linux.git/arch/x86/kernel/kvmclock.c, branch v6.0

x86/kvm: Don't waste kvmclock memory if there is nopv parameter

2022-04-13T17:37:19+00:00

When the "nopv" command line parameter is used, it should not waste
memory for kvmclock.

Signed-off-by: Wanpeng Li 
Message-Id: <1646727529-11774-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini

x86/kvmclock: Fix Hyper-V Isolated VM's boot issue when vCPUs > 64

2022-02-25T15:09:34+00:00

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() -> 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 >=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 > 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) 
Signed-off-by: Andrea Parri (Microsoft) 
Signed-off-by: Dexuan Cui 
Message-Id: <20220225084600.17817-1-decui@microsoft.com>
Signed-off-by: Paolo Bonzini

x86/kvm: Don't waste memory if kvmclock is disabled

2022-02-25T15:09:34+00:00

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 
Message-Id: <1645520523-30814-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini

x86/kvm: Silence per-cpu pr_info noise about KVM clocks and steal time

2022-01-07T15:44:43+00:00

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 
Message-Id: <20211209150938.3518-12-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini

x86/sev: Replace occurrences of sev_active() with cc_platform_has()

2021-10-04T09:46:58+00:00

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 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210928191009.32551-7-bp@alien8.de

x86/kvmclock: Move this_cpu_pvti into kvmclock.h

2021-09-30T08:08:01+00:00

There're other modules might use hv_clock_per_cpu variable like ptp_kvm,
so move it into kvmclock.h and export the symbol to make it visiable to
other modules.

Signed-off-by: Zelin Deng 
Cc: 
Message-Id: <1632892429-101194-2-git-send-email-zelin.deng@linux.alibaba.com>
Signed-off-by: Paolo Bonzini

x86/kvm: Disable all PV features on crash

2021-05-07T10:06:10+00:00

Crash shutdown handler only disables kvmclock and steal time, other PV
features remain active so we risk corrupting memory or getting some
side-effects in kdump kernel. Move crash handler to kvm.c and unify
with CPU offline.

Signed-off-by: Vitaly Kuznetsov 
Message-Id: <20210414123544.1060604-5-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini

x86/kvm: Disable kvmclock on all CPUs on shutdown

2021-05-07T10:06:10+00:00

Currenly, we disable kvmclock from machine_shutdown() hook and this
only happens for boot CPU. We need to disable it for all CPUs to
guard against memory corruption e.g. on restore from hibernate.

Note, writing '0' to kvmclock MSR doesn't clear memory location, it
just prevents hypervisor from updating the location so for the short
while after write and while CPU is still alive, the clock remains usable
and correct so we don't need to switch to some other clocksource.

Signed-off-by: Vitaly Kuznetsov 
Message-Id: <20210414123544.1060604-4-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini

Merge tag 'x86_alternatives_for_v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-04-26T16:01:29+00:00

Pull x86 alternatives/paravirt updates from Borislav Petkov:
 "First big cleanup to the paravirt infra to use alternatives and thus
  eliminate custom code patching.

  For that, the alternatives infrastructure is extended to accomodate
  paravirt's needs and, as a result, a lot of paravirt patching code
  goes away, leading to a sizeable cleanup and simplification.

  Work by Juergen Gross"

* tag 'x86_alternatives_for_v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/paravirt: Have only one paravirt patch function
  x86/paravirt: Switch functions with custom code to ALTERNATIVE
  x86/paravirt: Add new PVOP_ALT* macros to support pvops in ALTERNATIVEs
  x86/paravirt: Switch iret pvops to ALTERNATIVE
  x86/paravirt: Simplify paravirt macros
  x86/paravirt: Remove no longer needed 32-bit pvops cruft
  x86/paravirt: Add new features for paravirt patching
  x86/alternative: Use ALTERNATIVE_TERNARY() in _static_cpu_has()
  x86/alternative: Support ALTERNATIVE_TERNARY
  x86/alternative: Support not-feature
  x86/paravirt: Switch time pvops functions to use static_call()
  static_call: Add function to query current function
  static_call: Move struct static_call_key definition to static_call_types.h
  x86/alternative: Merge include files
  x86/alternative: Drop unused feature parameter from ALTINSTR_REPLACEMENT()

KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged

2021-03-12T18:18:16+00:00

# lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                88
On-line CPU(s) list:   0-63
Off-line CPU(s) list:  64-87

# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-5.10.0-rc3-tlinux2-0050+ root=/dev/mapper/cl-root ro
rd.lvm.lv=cl/root rhgb quiet console=ttyS0 LANG=en_US .UTF-8 no-kvmclock-vsyscall

# echo 1 > /sys/devices/system/cpu/cpu76/online
-bash: echo: write error: Cannot allocate memory

The per-cpu vsyscall pvclock data pointer assigns either an element of the
static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory
hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if
kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in
kvmclock_setup_percpu() which returns -ENOMEM. It's broken for no-vsyscall
and sometimes you end up with vsyscall disabled if the host does something
strange. This patch fixes it by allocating this dynamically memory
unconditionally even if vsyscall is disabled.

Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
Reported-by: Zelin Deng 
Cc: Brijesh Singh 
Cc: stable@vger.kernel.org#v4.19-rc5+
Signed-off-by: Wanpeng Li 
Message-Id: <1614130683-24137-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini