linux.git/arch/x86/kernel/kvmclock.c, branch v5.15

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

x86/paravirt: Switch time pvops functions to use static_call()

2021-03-11T15:17:52+00:00

The time pvops functions are the only ones left which might be
used in 32-bit mode and which return a 64-bit value.

Switch them to use the static_call() mechanism instead of pvops, as
this allows quite some simplification of the pvops implementation.

Signed-off-by: Juergen Gross 
Signed-off-by: Borislav Petkov 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20210311142319.4723-5-jgross@suse.com

x86/kvm: remove unused macro HV_CLOCK_SIZE

2020-11-16T18:14:21+00:00

This macro is useless, and could cause gcc warning:
arch/x86/kernel/kvmclock.c:47:0: warning: macro "HV_CLOCK_SIZE" is not
used [-Wunused-macros]
Let's remove it.

Signed-off-by: Alex Shi 
Cc: Paolo Bonzini 
Cc: Sean Christopherson 
Cc: Vitaly Kuznetsov 
Cc: Wanpeng Li 
Cc: Jim Mattson 
Cc: Joerg Roedel 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: x86@kernel.org
Cc: "H. Peter Anvin" 
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Message-Id: <1604651963-10067-1-git-send-email-alex.shi@linux.alibaba.com>
Signed-off-by: Paolo Bonzini

x86/vdso: Use generic VDSO clock mode storage

2020-02-17T13:40:23+00:00

Switch to the generic VDSO clock mode storage.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Vincenzo Frascino  (VDSO parts)
Acked-by: Juergen Gross  (Xen parts)
Acked-by: Paolo Bonzini  (KVM parts)
Link: https://lkml.kernel.org/r/20200207124403.152039903@linutronix.de

x86/vdso: Move VDSO clocksource state tracking to callback

2020-02-17T13:40:22+00:00

All architectures which use the generic VDSO code have their own storage
for the VDSO clock mode. That's pointless and just requires duplicate code.

X86 abuses the function which retrieves the architecture specific clock
mode storage to mark the clocksource as used in the VDSO. That's silly
because this is invoked on every tick when the VDSO data is updated.

Move this functionality to the clocksource::enable() callback so it gets
invoked once when the clocksource is installed. This allows to make the
clock mode storage generic.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Michael Kelley   (Hyper-V parts)
Reviewed-by: Vincenzo Frascino  (VDSO parts)
Acked-by: Juergen Gross  (Xen parts)
Link: https://lkml.kernel.org/r/20200207124402.934519777@linutronix.de

x86: kvmguest: use TSC clocksource if invariant TSC is exposed

2019-02-20T21:48:52+00:00

The invariant TSC bit has the following meaning:

"The time stamp counter in newer processors may support an enhancement,
referred to as invariant TSC. Processor's support for invariant TSC
is indicated by CPUID.80000007H:EDX[8]. The invariant TSC will run
at a constant rate in all ACPI P-, C-. and T-states. This is the
architectural behavior moving forward. On processors with invariant TSC
support, the OS may use the TSC for wall clock timer services (instead
of ACPI or HPET timers). TSC reads are much more efficient and do not
incur the overhead associated with a ring transition or access to a
platform resource."

IOW, TSC does not change frequency. In such case, and with
TSC scaling hardware available to handle migration, it is possible
to use the TSC clocksource directly, whose system calls are
faster.

Reduce the rating of kvmclock clocksource to allow TSC clocksource
to be the default if invariant TSC is exposed.

Signed-off-by: Marcelo Tosatti 

v2: Use feature bits and tsc_unstable() check (Sean Christopherson)
Signed-off-by: Paolo Bonzini