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From: Jim Mattson <jmattson@google.com>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Yang Weijiang <weijiang.yang@intel.com>,
	pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com,
	wei.w.wang@intel.com, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"kan.liang@linux.intel.com" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v5 06/13] KVM: x86/vmx: Save/Restore host MSR_ARCH_LBR_CTL state
Date: Wed, 14 Jul 2021 09:15:10 -0700	[thread overview]
Message-ID: <CALMp9eQF2ZAs0qNfmjpXAUNwiR8ESfUiA8AjA3uPbDMeX_Aotw@mail.gmail.com> (raw)
In-Reply-To: <cb4c1daa-f7a3-4f9c-fcdd-6a91e0dbcab4@gmail.com>

On Wed, Jul 14, 2021 at 6:33 AM Like Xu <like.xu.linux@gmail.com> wrote:
>
> On 14/7/2021 1:00 am, Jim Mattson wrote:

> > We have no such concept in our user space. Features that are not
> > migratable should clearly be identified as such by an appropriate KVM
> > API. At present, I don't believe there is such an API.
>
> I couldn't agree with you more on this point.

Maybe KVM_GET_SUPPORTED_CPUID could be made more useful if it took an
argument, such as 'MAX', 'MIGRATABLE', etc.

> We do have a code gap to make Arch LBR migratable for any KVM user.

Right. My point is that the feature as architected appears to be
migratable. Therefore, it would be reasonable for userspace to assume
that any KVM implementation that claims to support the feature (via
KVM_GET_SUPPORTED_CPUID) should support it in a fully migratable way
(i.e. if the hardware supports the guest LBR depth, then it should be
able to run the VM, without loss of functionality).

  reply	other threads:[~2021-07-14 16:15 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-09 10:04 [PATCH v5 00/13] Introduce Architectural LBR for vPMU Yang Weijiang
2021-07-09 10:04 ` [PATCH v5 01/13] perf/x86/intel: Fix the comment about guest LBR support on KVM Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 02/13] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 03/13] KVM: x86: Add arch LBR MSRs to msrs_to_save_all list Yang Weijiang
2021-07-09 18:24   ` Jim Mattson
2021-07-12  8:55     ` Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 04/13] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_DEPTH for guest Arch LBR Yang Weijiang
2021-07-09 20:35   ` Jim Mattson
2021-07-12  9:17     ` Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 05/13] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL " Yang Weijiang
2021-07-09 21:55   ` Jim Mattson
2021-07-12  9:36     ` Yang Weijiang
2021-07-12 10:10       ` Like Xu
2021-07-13  9:05         ` Yang Weijiang
2021-07-10  0:42   ` kernel test robot
2021-07-10  0:42     ` kernel test robot
2021-07-09 10:05 ` [PATCH v5 06/13] KVM: x86/vmx: Save/Restore host MSR_ARCH_LBR_CTL state Yang Weijiang
2021-07-09 22:54   ` Jim Mattson
2021-07-09 23:41     ` Jim Mattson
2021-07-12  9:53       ` Yang Weijiang
2021-07-12 10:19         ` Like Xu
2021-07-12 17:20           ` Jim Mattson
2021-07-12 17:45             ` Jim Mattson
2021-07-13  9:49               ` Like Xu
2021-07-13 17:00                 ` Jim Mattson
2021-07-14 13:33                   ` Like Xu
2021-07-14 16:15                     ` Jim Mattson [this message]
2021-07-13  9:53             ` Yang Weijiang
2021-07-12  9:50     ` Yang Weijiang
2021-07-12 17:23       ` Jim Mattson
2021-07-13  9:47         ` Yang Weijiang
2021-07-13 10:16           ` Like Xu
2021-07-13 17:12             ` Jim Mattson
2021-07-14 13:55               ` Like Xu
2021-07-09 10:05 ` [PATCH v5 07/13] KVM: x86/pmu: Refactor code to support guest Arch LBR Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 08/13] KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 09/13] KVM: x86: Report XSS as an MSR to be saved if there are supported features Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 10/13] KVM: x86: Refine the matching and clearing logic for supported_xss Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 11/13] KVM: x86: Add XSAVE Support for Architectural LBR Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 12/13] KVM: x86/vmx: Check Arch LBR config when return perf capabilities Yang Weijiang
2021-07-09 10:05 ` [PATCH v5 13/13] KVM: x86/cpuid: Advise Arch LBR feature in CPUID Yang Weijiang

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