<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/arch/x86/kernel/kvmclock.c, branch v6.8</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm</title>
<updated>2024-01-17T21:03:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-01-17T21:03:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=09d1c6a80f2cf94c6e70be919203473d4ab8e26c'/>
<id>09d1c6a80f2cf94c6e70be919203473d4ab8e26c</id>
<content type='text'>
Pull kvm updates from Paolo Bonzini:
 "Generic:

   - Use memdup_array_user() to harden against overflow.

   - Unconditionally advertise KVM_CAP_DEVICE_CTRL for all
     architectures.

   - Clean up Kconfigs that all KVM architectures were selecting

   - New functionality around "guest_memfd", a new userspace API that
     creates an anonymous file and returns a file descriptor that refers
     to it. guest_memfd files are bound to their owning virtual machine,
     cannot be mapped, read, or written by userspace, and cannot be
     resized. guest_memfd files do however support PUNCH_HOLE, which can
     be used to switch a memory area between guest_memfd and regular
     anonymous memory.

   - New ioctl KVM_SET_MEMORY_ATTRIBUTES allowing userspace to specify
     per-page attributes for a given page of guest memory; right now the
     only attribute is whether the guest expects to access memory via
     guest_memfd or not, which in Confidential SVMs backed by SEV-SNP,
     TDX or ARM64 pKVM is checked by firmware or hypervisor that
     guarantees confidentiality (AMD PSP, Intel TDX module, or EL2 in
     the case of pKVM).

  x86:

   - Support for "software-protected VMs" that can use the new
     guest_memfd and page attributes infrastructure. This is mostly
     useful for testing, since there is no pKVM-like infrastructure to
     provide a meaningfully reduced TCB.

   - Fix a relatively benign off-by-one error when splitting huge pages
     during CLEAR_DIRTY_LOG.

   - Fix a bug where KVM could incorrectly test-and-clear dirty bits in
     non-leaf TDP MMU SPTEs if a racing thread replaces a huge SPTE with
     a non-huge SPTE.

   - Use more generic lockdep assertions in paths that don't actually
     care about whether the caller is a reader or a writer.

   - let Xen guests opt out of having PV clock reported as "based on a
     stable TSC", because some of them don't expect the "TSC stable" bit
     (added to the pvclock ABI by KVM, but never set by Xen) to be set.

   - Revert a bogus, made-up nested SVM consistency check for
     TLB_CONTROL.

   - Advertise flush-by-ASID support for nSVM unconditionally, as KVM
     always flushes on nested transitions, i.e. always satisfies flush
     requests. This allows running bleeding edge versions of VMware
     Workstation on top of KVM.

   - Sanity check that the CPU supports flush-by-ASID when enabling SEV
     support.

   - On AMD machines with vNMI, always rely on hardware instead of
     intercepting IRET in some cases to detect unmasking of NMIs

   - Support for virtualizing Linear Address Masking (LAM)

   - Fix a variety of vPMU bugs where KVM fail to stop/reset counters
     and other state prior to refreshing the vPMU model.

   - Fix a double-overflow PMU bug by tracking emulated counter events
     using a dedicated field instead of snapshotting the "previous"
     counter. If the hardware PMC count triggers overflow that is
     recognized in the same VM-Exit that KVM manually bumps an event
     count, KVM would pend PMIs for both the hardware-triggered overflow
     and for KVM-triggered overflow.

   - Turn off KVM_WERROR by default for all configs so that it's not
     inadvertantly enabled by non-KVM developers, which can be
     problematic for subsystems that require no regressions for W=1
     builds.

   - Advertise all of the host-supported CPUID bits that enumerate
     IA32_SPEC_CTRL "features".

   - Don't force a masterclock update when a vCPU synchronizes to the
     current TSC generation, as updating the masterclock can cause
     kvmclock's time to "jump" unexpectedly, e.g. when userspace
     hotplugs a pre-created vCPU.

   - Use RIP-relative address to read kvm_rebooting in the VM-Enter
     fault paths, partly as a super minor optimization, but mostly to
     make KVM play nice with position independent executable builds.

   - Guard KVM-on-HyperV's range-based TLB flush hooks with an #ifdef on
     CONFIG_HYPERV as a minor optimization, and to self-document the
     code.

   - Add CONFIG_KVM_HYPERV to allow disabling KVM support for HyperV
     "emulation" at build time.

  ARM64:

   - LPA2 support, adding 52bit IPA/PA capability for 4kB and 16kB base
     granule sizes. Branch shared with the arm64 tree.

   - Large Fine-Grained Trap rework, bringing some sanity to the
     feature, although there is more to come. This comes with a prefix
     branch shared with the arm64 tree.

   - Some additional Nested Virtualization groundwork, mostly
     introducing the NV2 VNCR support and retargetting the NV support to
     that version of the architecture.

   - A small set of vgic fixes and associated cleanups.

  Loongarch:

   - Optimization for memslot hugepage checking

   - Cleanup and fix some HW/SW timer issues

   - Add LSX/LASX (128bit/256bit SIMD) support

  RISC-V:

   - KVM_GET_REG_LIST improvement for vector registers

   - Generate ISA extension reg_list using macros in get-reg-list
     selftest

   - Support for reporting steal time along with selftest

  s390:

   - Bugfixes

  Selftests:

   - Fix an annoying goof where the NX hugepage test prints out garbage
     instead of the magic token needed to run the test.

   - Fix build errors when a header is delete/moved due to a missing
     flag in the Makefile.

   - Detect if KVM bugged/killed a selftest's VM and print out a helpful
     message instead of complaining that a random ioctl() failed.

   - Annotate the guest printf/assert helpers with __printf(), and fix
     the various bugs that were lurking due to lack of said annotation"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (185 commits)
  x86/kvm: Do not try to disable kvmclock if it was not enabled
  KVM: x86: add missing "depends on KVM"
  KVM: fix direction of dependency on MMU notifiers
  KVM: introduce CONFIG_KVM_COMMON
  KVM: arm64: Add missing memory barriers when switching to pKVM's hyp pgd
  KVM: arm64: vgic-its: Avoid potential UAF in LPI translation cache
  RISC-V: KVM: selftests: Add get-reg-list test for STA registers
  RISC-V: KVM: selftests: Add steal_time test support
  RISC-V: KVM: selftests: Add guest_sbi_probe_extension
  RISC-V: KVM: selftests: Move sbi_ecall to processor.c
  RISC-V: KVM: Implement SBI STA extension
  RISC-V: KVM: Add support for SBI STA registers
  RISC-V: KVM: Add support for SBI extension registers
  RISC-V: KVM: Add SBI STA info to vcpu_arch
  RISC-V: KVM: Add steal-update vcpu request
  RISC-V: KVM: Add SBI STA extension skeleton
  RISC-V: paravirt: Implement steal-time support
  RISC-V: Add SBI STA extension definitions
  RISC-V: paravirt: Add skeleton for pv-time support
  RISC-V: KVM: Fix indentation in kvm_riscv_vcpu_set_reg_csr()
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kvm updates from Paolo Bonzini:
 "Generic:

   - Use memdup_array_user() to harden against overflow.

   - Unconditionally advertise KVM_CAP_DEVICE_CTRL for all
     architectures.

   - Clean up Kconfigs that all KVM architectures were selecting

   - New functionality around "guest_memfd", a new userspace API that
     creates an anonymous file and returns a file descriptor that refers
     to it. guest_memfd files are bound to their owning virtual machine,
     cannot be mapped, read, or written by userspace, and cannot be
     resized. guest_memfd files do however support PUNCH_HOLE, which can
     be used to switch a memory area between guest_memfd and regular
     anonymous memory.

   - New ioctl KVM_SET_MEMORY_ATTRIBUTES allowing userspace to specify
     per-page attributes for a given page of guest memory; right now the
     only attribute is whether the guest expects to access memory via
     guest_memfd or not, which in Confidential SVMs backed by SEV-SNP,
     TDX or ARM64 pKVM is checked by firmware or hypervisor that
     guarantees confidentiality (AMD PSP, Intel TDX module, or EL2 in
     the case of pKVM).

  x86:

   - Support for "software-protected VMs" that can use the new
     guest_memfd and page attributes infrastructure. This is mostly
     useful for testing, since there is no pKVM-like infrastructure to
     provide a meaningfully reduced TCB.

   - Fix a relatively benign off-by-one error when splitting huge pages
     during CLEAR_DIRTY_LOG.

   - Fix a bug where KVM could incorrectly test-and-clear dirty bits in
     non-leaf TDP MMU SPTEs if a racing thread replaces a huge SPTE with
     a non-huge SPTE.

   - Use more generic lockdep assertions in paths that don't actually
     care about whether the caller is a reader or a writer.

   - let Xen guests opt out of having PV clock reported as "based on a
     stable TSC", because some of them don't expect the "TSC stable" bit
     (added to the pvclock ABI by KVM, but never set by Xen) to be set.

   - Revert a bogus, made-up nested SVM consistency check for
     TLB_CONTROL.

   - Advertise flush-by-ASID support for nSVM unconditionally, as KVM
     always flushes on nested transitions, i.e. always satisfies flush
     requests. This allows running bleeding edge versions of VMware
     Workstation on top of KVM.

   - Sanity check that the CPU supports flush-by-ASID when enabling SEV
     support.

   - On AMD machines with vNMI, always rely on hardware instead of
     intercepting IRET in some cases to detect unmasking of NMIs

   - Support for virtualizing Linear Address Masking (LAM)

   - Fix a variety of vPMU bugs where KVM fail to stop/reset counters
     and other state prior to refreshing the vPMU model.

   - Fix a double-overflow PMU bug by tracking emulated counter events
     using a dedicated field instead of snapshotting the "previous"
     counter. If the hardware PMC count triggers overflow that is
     recognized in the same VM-Exit that KVM manually bumps an event
     count, KVM would pend PMIs for both the hardware-triggered overflow
     and for KVM-triggered overflow.

   - Turn off KVM_WERROR by default for all configs so that it's not
     inadvertantly enabled by non-KVM developers, which can be
     problematic for subsystems that require no regressions for W=1
     builds.

   - Advertise all of the host-supported CPUID bits that enumerate
     IA32_SPEC_CTRL "features".

   - Don't force a masterclock update when a vCPU synchronizes to the
     current TSC generation, as updating the masterclock can cause
     kvmclock's time to "jump" unexpectedly, e.g. when userspace
     hotplugs a pre-created vCPU.

   - Use RIP-relative address to read kvm_rebooting in the VM-Enter
     fault paths, partly as a super minor optimization, but mostly to
     make KVM play nice with position independent executable builds.

   - Guard KVM-on-HyperV's range-based TLB flush hooks with an #ifdef on
     CONFIG_HYPERV as a minor optimization, and to self-document the
     code.

   - Add CONFIG_KVM_HYPERV to allow disabling KVM support for HyperV
     "emulation" at build time.

  ARM64:

   - LPA2 support, adding 52bit IPA/PA capability for 4kB and 16kB base
     granule sizes. Branch shared with the arm64 tree.

   - Large Fine-Grained Trap rework, bringing some sanity to the
     feature, although there is more to come. This comes with a prefix
     branch shared with the arm64 tree.

   - Some additional Nested Virtualization groundwork, mostly
     introducing the NV2 VNCR support and retargetting the NV support to
     that version of the architecture.

   - A small set of vgic fixes and associated cleanups.

  Loongarch:

   - Optimization for memslot hugepage checking

   - Cleanup and fix some HW/SW timer issues

   - Add LSX/LASX (128bit/256bit SIMD) support

  RISC-V:

   - KVM_GET_REG_LIST improvement for vector registers

   - Generate ISA extension reg_list using macros in get-reg-list
     selftest

   - Support for reporting steal time along with selftest

  s390:

   - Bugfixes

  Selftests:

   - Fix an annoying goof where the NX hugepage test prints out garbage
     instead of the magic token needed to run the test.

   - Fix build errors when a header is delete/moved due to a missing
     flag in the Makefile.

   - Detect if KVM bugged/killed a selftest's VM and print out a helpful
     message instead of complaining that a random ioctl() failed.

   - Annotate the guest printf/assert helpers with __printf(), and fix
     the various bugs that were lurking due to lack of said annotation"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (185 commits)
  x86/kvm: Do not try to disable kvmclock if it was not enabled
  KVM: x86: add missing "depends on KVM"
  KVM: fix direction of dependency on MMU notifiers
  KVM: introduce CONFIG_KVM_COMMON
  KVM: arm64: Add missing memory barriers when switching to pKVM's hyp pgd
  KVM: arm64: vgic-its: Avoid potential UAF in LPI translation cache
  RISC-V: KVM: selftests: Add get-reg-list test for STA registers
  RISC-V: KVM: selftests: Add steal_time test support
  RISC-V: KVM: selftests: Add guest_sbi_probe_extension
  RISC-V: KVM: selftests: Move sbi_ecall to processor.c
  RISC-V: KVM: Implement SBI STA extension
  RISC-V: KVM: Add support for SBI STA registers
  RISC-V: KVM: Add support for SBI extension registers
  RISC-V: KVM: Add SBI STA info to vcpu_arch
  RISC-V: KVM: Add steal-update vcpu request
  RISC-V: KVM: Add SBI STA extension skeleton
  RISC-V: paravirt: Implement steal-time support
  RISC-V: Add SBI STA extension definitions
  RISC-V: paravirt: Add skeleton for pv-time support
  RISC-V: KVM: Fix indentation in kvm_riscv_vcpu_set_reg_csr()
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/kvm: Do not try to disable kvmclock if it was not enabled</title>
<updated>2024-01-08T17:14:41+00:00</updated>
<author>
<name>Kirill A. Shutemov</name>
<email>kirill.shutemov@linux.intel.com</email>
</author>
<published>2023-12-05T00:45:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=1c6d984f523f67ecfad1083bb04c55d91977bb15'/>
<id>1c6d984f523f67ecfad1083bb04c55d91977bb15</id>
<content type='text'>
kvm_guest_cpu_offline() tries to disable kvmclock regardless if it is
present in the VM. It leads to write to a MSR that doesn't exist on some
configurations, namely in TDX guest:

	unchecked MSR access error: WRMSR to 0x12 (tried to write 0x0000000000000000)
	at rIP: 0xffffffff8110687c (kvmclock_disable+0x1c/0x30)

kvmclock enabling is gated by CLOCKSOURCE and CLOCKSOURCE2 KVM paravirt
features.

Do not disable kvmclock if it was not enabled.

Signed-off-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
Reviewed-by: Sean Christopherson &lt;seanjc@google.com&gt;
Reviewed-by: Vitaly Kuznetsov &lt;vkuznets@redhat.com&gt;
Cc: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Cc: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Cc: stable@vger.kernel.org
Message-Id: &lt;20231205004510.27164-6-kirill.shutemov@linux.intel.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
kvm_guest_cpu_offline() tries to disable kvmclock regardless if it is
present in the VM. It leads to write to a MSR that doesn't exist on some
configurations, namely in TDX guest:

	unchecked MSR access error: WRMSR to 0x12 (tried to write 0x0000000000000000)
	at rIP: 0xffffffff8110687c (kvmclock_disable+0x1c/0x30)

kvmclock enabling is gated by CLOCKSOURCE and CLOCKSOURCE2 KVM paravirt
features.

Do not disable kvmclock if it was not enabled.

Signed-off-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
Reviewed-by: Sean Christopherson &lt;seanjc@google.com&gt;
Reviewed-by: Vitaly Kuznetsov &lt;vkuznets@redhat.com&gt;
Cc: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Cc: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Cc: stable@vger.kernel.org
Message-Id: &lt;20231205004510.27164-6-kirill.shutemov@linux.intel.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>arch/x86: Fix typos</title>
<updated>2024-01-03T10:46:22+00:00</updated>
<author>
<name>Bjorn Helgaas</name>
<email>bhelgaas@google.com</email>
</author>
<published>2024-01-03T00:40:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=54aa699e8094efb7d7675fefbc03dfce24f98456'/>
<id>54aa699e8094efb7d7675fefbc03dfce24f98456</id>
<content type='text'>
Fix typos, most reported by "codespell arch/x86".  Only touches comments,
no code changes.

Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fix typos, most reported by "codespell arch/x86".  Only touches comments,
no code changes.

Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/tsc: Provide sched_clock_noinstr()</title>
<updated>2023-06-05T19:11:08+00:00</updated>
<author>
<name>Peter Zijlstra</name>
<email>peterz@infradead.org</email>
</author>
<published>2023-05-19T10:21:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=5c5e9a2b25b6a79d4b7a5f2a54d02ef1c36dc35a'/>
<id>5c5e9a2b25b6a79d4b7a5f2a54d02ef1c36dc35a</id>
<content type='text'>
With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by providing a noinstr sched_clock_noinstr()
function.

Specifically, preempt_enable_*() calls out to schedule(), which upsets
noinstr validation efforts.

  vmlinux.o: warning: objtool: native_sched_clock+0x96: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
  vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Michael Kelley &lt;mikelley@microsoft.com&gt;  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.910937674@infradead.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by providing a noinstr sched_clock_noinstr()
function.

Specifically, preempt_enable_*() calls out to schedule(), which upsets
noinstr validation efforts.

  vmlinux.o: warning: objtool: native_sched_clock+0x96: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
  vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Tested-by: Michael Kelley &lt;mikelley@microsoft.com&gt;  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.910937674@infradead.org
</pre>
</div>
</content>
</entry>
<entry>
<title>sched/clock/x86: Mark sched_clock() noinstr</title>
<updated>2023-01-31T14:01:47+00:00</updated>
<author>
<name>Peter Zijlstra</name>
<email>peterz@infradead.org</email>
</author>
<published>2023-01-26T15:08:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=8739c6811572b087decd561f96382087402cc343'/>
<id>8739c6811572b087decd561f96382087402cc343</id>
<content type='text'>
In order to use sched_clock() from noinstr code, mark it and all it's
implenentations noinstr.

The whole pvclock thing (used by KVM/Xen) is a bit of a pain,
since it calls out to watchdogs, create a
pvclock_clocksource_read_nowd() variant doesn't do that and can be
noinstr.

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Link: https://lore.kernel.org/r/20230126151323.702003578@infradead.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In order to use sched_clock() from noinstr code, mark it and all it's
implenentations noinstr.

The whole pvclock thing (used by KVM/Xen) is a bit of a pain,
since it calls out to watchdogs, create a
pvclock_clocksource_read_nowd() variant doesn't do that and can be
noinstr.

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Link: https://lore.kernel.org/r/20230126151323.702003578@infradead.org
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/kvm: Don't waste kvmclock memory if there is nopv parameter</title>
<updated>2022-04-13T17:37:19+00:00</updated>
<author>
<name>Wanpeng Li</name>
<email>wanpengli@tencent.com</email>
</author>
<published>2022-03-08T08:18:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=77d727926607ba42f0c4ba82baaec1076e8cbebf'/>
<id>77d727926607ba42f0c4ba82baaec1076e8cbebf</id>
<content type='text'>
When the "nopv" command line parameter is used, it should not waste
memory for kvmclock.

Signed-off-by: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Message-Id: &lt;1646727529-11774-1-git-send-email-wanpengli@tencent.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When the "nopv" command line parameter is used, it should not waste
memory for kvmclock.

Signed-off-by: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Message-Id: &lt;1646727529-11774-1-git-send-email-wanpengli@tencent.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/kvmclock: Fix Hyper-V Isolated VM's boot issue when vCPUs &gt; 64</title>
<updated>2022-02-25T15:09:34+00:00</updated>
<author>
<name>Dexuan Cui</name>
<email>decui@microsoft.com</email>
</author>
<published>2022-02-25T08:46:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=92e68cc558774de01024c18e8b35cdce4731c910'/>
<id>92e68cc558774de01024c18e8b35cdce4731c910</id>
<content type='text'>
When Linux runs as an Isolated VM on Hyper-V, it supports AMD SEV-SNP
but it's partially enlightened, i.e. cc_platform_has(
CC_ATTR_GUEST_MEM_ENCRYPT) is true but sev_active() is false.

Commit 4d96f9109109 per se is good, but with it now
kvm_setup_vsyscall_timeinfo() -&gt; kvmclock_init_mem() calls
set_memory_decrypted(), and later gets stuck when trying to zere out
the pages pointed by 'hvclock_mem', if Linux runs as an Isolated VM on
Hyper-V. The cause is that here now the Linux VM should no longer access
the original guest physical addrss (GPA); instead the VM should do
memremap() and access the original GPA + ms_hyperv.shared_gpa_boundary:
see the example code in drivers/hv/connection.c: vmbus_connect() or
drivers/hv/ring_buffer.c: hv_ringbuffer_init(). If the VM tries to
access the original GPA, it keepts getting injected a fault by Hyper-V
and gets stuck there.

Here the issue happens only when the VM has &gt;=65 vCPUs, because the
global static array hv_clock_boot[] can hold 64 "struct
pvclock_vsyscall_time_info" (the sizeof of the struct is 64 bytes), so
kvmclock_init_mem() only allocates memory in the case of vCPUs &gt; 64.

Since the 'hvclock_mem' pages are only useful when the kvm clock is
supported by the underlying hypervisor, fix the issue by returning
early when Linux VM runs on Hyper-V, which doesn't support kvm clock.

Fixes: 4d96f9109109 ("x86/sev: Replace occurrences of sev_active() with cc_platform_has()")
Tested-by: Andrea Parri (Microsoft) &lt;parri.andrea@gmail.com&gt;
Signed-off-by: Andrea Parri (Microsoft) &lt;parri.andrea@gmail.com&gt;
Signed-off-by: Dexuan Cui &lt;decui@microsoft.com&gt;
Message-Id: &lt;20220225084600.17817-1-decui@microsoft.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When Linux runs as an Isolated VM on Hyper-V, it supports AMD SEV-SNP
but it's partially enlightened, i.e. cc_platform_has(
CC_ATTR_GUEST_MEM_ENCRYPT) is true but sev_active() is false.

Commit 4d96f9109109 per se is good, but with it now
kvm_setup_vsyscall_timeinfo() -&gt; kvmclock_init_mem() calls
set_memory_decrypted(), and later gets stuck when trying to zere out
the pages pointed by 'hvclock_mem', if Linux runs as an Isolated VM on
Hyper-V. The cause is that here now the Linux VM should no longer access
the original guest physical addrss (GPA); instead the VM should do
memremap() and access the original GPA + ms_hyperv.shared_gpa_boundary:
see the example code in drivers/hv/connection.c: vmbus_connect() or
drivers/hv/ring_buffer.c: hv_ringbuffer_init(). If the VM tries to
access the original GPA, it keepts getting injected a fault by Hyper-V
and gets stuck there.

Here the issue happens only when the VM has &gt;=65 vCPUs, because the
global static array hv_clock_boot[] can hold 64 "struct
pvclock_vsyscall_time_info" (the sizeof of the struct is 64 bytes), so
kvmclock_init_mem() only allocates memory in the case of vCPUs &gt; 64.

Since the 'hvclock_mem' pages are only useful when the kvm clock is
supported by the underlying hypervisor, fix the issue by returning
early when Linux VM runs on Hyper-V, which doesn't support kvm clock.

Fixes: 4d96f9109109 ("x86/sev: Replace occurrences of sev_active() with cc_platform_has()")
Tested-by: Andrea Parri (Microsoft) &lt;parri.andrea@gmail.com&gt;
Signed-off-by: Andrea Parri (Microsoft) &lt;parri.andrea@gmail.com&gt;
Signed-off-by: Dexuan Cui &lt;decui@microsoft.com&gt;
Message-Id: &lt;20220225084600.17817-1-decui@microsoft.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/kvm: Don't waste memory if kvmclock is disabled</title>
<updated>2022-02-25T15:09:34+00:00</updated>
<author>
<name>Wanpeng Li</name>
<email>wanpengli@tencent.com</email>
</author>
<published>2022-02-22T09:02:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=3c51d0a6c761c2025c6db1ed4d3a7273167bf899'/>
<id>3c51d0a6c761c2025c6db1ed4d3a7273167bf899</id>
<content type='text'>
Even if "no-kvmclock" is passed in cmdline parameter, the guest kernel
still allocates hvclock_mem which is scaled by the number of vCPUs,
let's check kvmclock enable in advance to avoid this memory waste.

Signed-off-by: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Message-Id: &lt;1645520523-30814-1-git-send-email-wanpengli@tencent.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Even if "no-kvmclock" is passed in cmdline parameter, the guest kernel
still allocates hvclock_mem which is scaled by the number of vCPUs,
let's check kvmclock enable in advance to avoid this memory waste.

Signed-off-by: Wanpeng Li &lt;wanpengli@tencent.com&gt;
Message-Id: &lt;1645520523-30814-1-git-send-email-wanpengli@tencent.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/kvm: Silence per-cpu pr_info noise about KVM clocks and steal time</title>
<updated>2022-01-07T15:44:43+00:00</updated>
<author>
<name>David Woodhouse</name>
<email>dwmw@amazon.co.uk</email>
</author>
<published>2021-12-09T15:09:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f3f26dae05e39f0f286f588669b54d49b61dcfb8'/>
<id>f3f26dae05e39f0f286f588669b54d49b61dcfb8</id>
<content type='text'>
I made the actual CPU bringup go nice and fast... and then Linux spends
half a minute printing stupid nonsense about clocks and steal time for
each of 256 vCPUs. Don't do that. Nobody cares.

Signed-off-by: David Woodhouse &lt;dwmw@amazon.co.uk&gt;
Message-Id: &lt;20211209150938.3518-12-dwmw2@infradead.org&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
I made the actual CPU bringup go nice and fast... and then Linux spends
half a minute printing stupid nonsense about clocks and steal time for
each of 256 vCPUs. Don't do that. Nobody cares.

Signed-off-by: David Woodhouse &lt;dwmw@amazon.co.uk&gt;
Message-Id: &lt;20211209150938.3518-12-dwmw2@infradead.org&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/sev: Replace occurrences of sev_active() with cc_platform_has()</title>
<updated>2021-10-04T09:46:58+00:00</updated>
<author>
<name>Tom Lendacky</name>
<email>thomas.lendacky@amd.com</email>
</author>
<published>2021-09-08T22:58:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=4d96f9109109be93618050a50cabb8df7c931ba7'/>
<id>4d96f9109109be93618050a50cabb8df7c931ba7</id>
<content type='text'>
Replace uses of sev_active() with the more generic cc_platform_has()
using CC_ATTR_GUEST_MEM_ENCRYPT. If future support is added for other
memory encryption technologies, the use of CC_ATTR_GUEST_MEM_ENCRYPT
can be updated, as required.

Signed-off-by: Tom Lendacky &lt;thomas.lendacky@amd.com&gt;
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Link: https://lkml.kernel.org/r/20210928191009.32551-7-bp@alien8.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Replace uses of sev_active() with the more generic cc_platform_has()
using CC_ATTR_GUEST_MEM_ENCRYPT. If future support is added for other
memory encryption technologies, the use of CC_ATTR_GUEST_MEM_ENCRYPT
can be updated, as required.

Signed-off-by: Tom Lendacky &lt;thomas.lendacky@amd.com&gt;
Signed-off-by: Borislav Petkov &lt;bp@suse.de&gt;
Link: https://lkml.kernel.org/r/20210928191009.32551-7-bp@alien8.de
</pre>
</div>
</content>
</entry>
</feed>
