From: Peter Zijlstra <peterz@infradead.org>
To: Manali Shukla <manali.shukla@amd.com>
Cc: kvm@vger.kernel.org, seanjc@google.com,
linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org,
x86@kernel.org, pbonzini@redhat.com, bp@alien8.de,
santosh.shukla@amd.com, ravi.bangoria@amd.com,
thomas.lendacky@amd.com, nikunj@amd.com
Subject: Re: [PATCH 00/13] Implement support for IBS virtualization
Date: Wed, 6 Sep 2023 21:56:19 +0200 [thread overview]
Message-ID: <20230906195619.GD28278@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <012c9897-51d7-87d3-e0e5-3856fa9644e5@amd.com>
On Wed, Sep 06, 2023 at 09:08:25PM +0530, Manali Shukla wrote:
> Hi Peter,
>
> Thank you for looking into this.
>
> On 9/5/2023 9:17 PM, Peter Zijlstra wrote:
> > On Mon, Sep 04, 2023 at 09:53:34AM +0000, Manali Shukla wrote:
> >
> >> Note that, since IBS registers are swap type C [2], the hypervisor is
> >> responsible for saving and restoring of IBS host state. Hypervisor
> >> does so only when IBS is active on the host to avoid unnecessary
> >> rdmsrs/wrmsrs. Hypervisor needs to disable host IBS before saving the
> >> state and enter the guest. After a guest exit, the hypervisor needs to
> >> restore host IBS state and re-enable IBS.
> >
> > Why do you think it is OK for a guest to disable the host IBS when
> > entering a guest? Perhaps the host was wanting to profile the guest.
> >
>
> 1. Since IBS registers are of swap type C [1], only guest state is saved
> and restored by the hardware. Host state needs to be saved and restored by
> hypervisor. In order to save IBS registers correctly, IBS needs to be
> disabled before saving the IBS registers.
>
> 2. As per APM [2],
> "When a VMRUN is executed to an SEV-ES guest with IBS virtualization enabled, the
> IbsFetchCtl[IbsFetchEn] and IbsOpCtl[IbsOpEn] MSR bits must be 0. If either of
> these bits are not 0, the VMRUN will fail with a VMEXIT_INVALID error code."
> This is enforced by hardware on SEV-ES guests when VIBS is enabled on SEV-ES
> guests.
I'm not sure I'm fluent in virt speak (in fact, I'm sure I'm not). Is
the above saying that a host can never IBS profile a guest?
Does the current IBS thing assert perf_event_attr::exclude_guest is set?
I can't quickly find anything :-(
next prev parent reply other threads:[~2023-09-06 19:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-04 9:53 [PATCH 00/13] Implement support for IBS virtualization Manali Shukla
2023-09-04 9:53 ` [PATCH 01/13] KVM: Add KVM_GET_LAPIC_W_EXTAPIC and KVM_SET_LAPIC_W_EXTAPIC for extapic Manali Shukla
2023-09-12 1:47 ` Chao Gao
2023-09-04 9:53 ` [PATCH 02/13] x86/cpufeatures: Add CPUID feature bit for Extended LVT Manali Shukla
2023-09-04 9:53 ` [PATCH 03/13] KVM: x86: Add emulation support for Extented LVT registers Manali Shukla
2023-09-12 2:36 ` Chao Gao
2023-09-04 9:53 ` [PATCH 04/13] x86/cpufeatures: Add CPUID feature bit for virtualized IBS Manali Shukla
2023-09-04 9:53 ` [PATCH 05/13] KVM: x86/cpuid: Add a KVM-only leaf for IBS capabilities Manali Shukla
2023-09-04 9:53 ` [PATCH 06/13] KVM: x86: Extend CPUID range to include new leaf Manali Shukla
2023-09-12 2:46 ` Chao Gao
2023-09-04 9:53 ` [PATCH 07/13] KVM: SVM: Extend VMCB area for virtualized IBS registers Manali Shukla
2023-09-12 2:50 ` Chao Gao
2023-09-04 9:53 ` [PATCH 08/13] perf/x86/amd: Add framework to save/restore host IBS state Manali Shukla
2023-09-05 14:54 ` Tom Lendacky
2023-09-04 9:53 ` [PATCH 09/13] KVM: SVM: add support for IBS virtualization for non SEV-ES guests Manali Shukla
2023-09-05 15:30 ` Tom Lendacky
2023-09-06 1:51 ` Alexey Kardashevskiy
2023-09-12 3:09 ` Chao Gao
2023-09-04 9:53 ` [PATCH 10/13] x86/cpufeatures: Add CPUID feature bit for VIBS in SEV-ES guest Manali Shukla
2023-09-04 9:53 ` [PATCH 11/13] KVM: SVM: Add support for IBS virtualization for SEV-ES guests Manali Shukla
2023-09-05 15:43 ` Tom Lendacky
2023-09-04 9:53 ` [PATCH 12/13] KVM: SVM: Enable IBS virtualization on non SEV-ES and " Manali Shukla
2023-09-05 16:00 ` Tom Lendacky
2023-09-12 3:30 ` Chao Gao
2023-09-04 9:53 ` [PATCH 13/13] KVM: x86: nSVM: Implement support for nested IBS virtualization Manali Shukla
2023-09-05 15:47 ` [PATCH 00/13] Implement support for " Peter Zijlstra
2023-09-06 15:38 ` Manali Shukla
2023-09-06 19:56 ` Peter Zijlstra [this message]
2023-09-07 15:49 ` Manali Shukla
2023-09-08 13:31 ` Peter Zijlstra
2023-09-11 12:32 ` Manali Shukla
2023-09-28 11:18 ` Manali Shukla
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