lkml.org 
[lkml]   [2020]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH][v6] KVM: X86: support APERF/MPERF registers
From
Date
Hi RongQing,

On 2020/6/5 9:44, Li RongQing wrote:
> Guest kernel reports a fixed cpu frequency in /proc/cpuinfo,
> this is confused to user when turbo is enable, and aperf/mperf
> can be used to show current cpu frequency after 7d5905dc14a
> "(x86 / CPU: Always show current CPU frequency in /proc/cpuinfo)"
> so guest should support aperf/mperf capability
>
> This patch implements aperf/mperf by three mode: none, software
> emulation, and pass-through
>
> None: default mode, guest does not support aperf/mperf
s/None/Note
>
> Software emulation: the period of aperf/mperf in guest mode are
> accumulated as emulated value
>
> Pass-though: it is only suitable for KVM_HINTS_REALTIME, Because
> that hint guarantees we have a 1:1 vCPU:CPU binding and guaranteed
> no over-commit.
The flag "KVM_HINTS_REALTIME 0" (in the Documentation/virt/kvm/cpuid.rst)
is claimed as "guest checks this feature bit to determine that vCPUs are never
preempted for an unlimited time allowing optimizations".

I couldn't see its relationship with "1:1 vCPU: pCPU binding".
The patch doesn't check this flag as well for your pass-through purpose.

Thanks,
Like Xu
>
> And a per-VM capability is added to configure aperfmperf mode
>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> Signed-off-by: Chai Wen <chaiwen@baidu.com>
> Signed-off-by: Jia Lina <jialina01@baidu.com>
> ---
> diff v5:
> return error if guest is configured with mperf/aperf, but host cpu has not
>
> diff v4:
> fix maybe-uninitialized warning
>
> diff v3:
> fix interception of MSR_IA32_MPERF/APERF in svm
>
> diff v2:
> support aperfmperf pass though
> move common codes to kvm_get_msr_common
>
> diff v1:
> 1. support AMD, but not test
> 2. support per-vm capability to enable
>
>
> Documentation/virt/kvm/api.rst | 10 ++++++++++
> arch/x86/include/asm/kvm_host.h | 11 +++++++++++
> arch/x86/kvm/cpuid.c | 15 ++++++++++++++-
> arch/x86/kvm/svm/svm.c | 8 ++++++++
> arch/x86/kvm/vmx/vmx.c | 6 ++++++
> arch/x86/kvm/x86.c | 42 +++++++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/x86.h | 15 +++++++++++++++
> include/uapi/linux/kvm.h | 1 +
> 8 files changed, 107 insertions(+), 1 deletion(-)

\
 
 \ /
  Last update: 2020-06-05 04:33    [W:0.087 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site