Message-ID: <1b6740e6-677a-fbad-e7ed-a9cf89badfec@amd.com>
Date:   Wed, 15 Mar 2023 10:35:52 +0530
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Subject: Re: [RFC PATCH kernel 2/2] KVM: SEV: PreventHostIBS enablement for
 SEV-ES and SNP guest
To:     Manali Shukla <manali.shukla@amd.com>, linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
        jolsa@kernel.org, namhyung@kernel.org, tglx@linutronix.de,
        bp@alien8.de, dave.hansen@linux.intel.com, seanjc@google.com,
        pbonzini@redhat.com, jpoimboe@kernel.org,
        pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com,
        sandipan.das@amd.com, jmattson@google.com, thomas.lendacky@amd.com,
        ravi.bangoria@amd.com, eranian@google.com, irogers@google.com,
        kvm@vger.kernel.org, x86@kernel.org,
        linux-perf-users@vger.kernel.org
References: <20230206060545.628502-1-manali.shukla@amd.com>
 <20230206060545.628502-3-manali.shukla@amd.com>
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From:   "Nikunj A. Dadhania" <nikunj@amd.com>
In-Reply-To: <20230206060545.628502-3-manali.shukla@amd.com>
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On 06/02/23 11:35, Manali Shukla wrote:
> Currently, the hypervisor is able to inspect instruction based samples
> from a guest and gather execution information. SEV-ES and SNP guests
> can disallow the use of instruction based sampling by hypervisor by
> enabling the PreventHostIBS feature for the guest.  (More information
> in Section 15.36.17 APM Volume 2)
> 
> The MSR_AMD64_IBSFETCHCTL[IbsFetchEn] and MSR_AMD64_IBSOPCTL[IbsOpEn]
> bits need to be disabled before VMRUN is called when PreventHostIBS
> feature is enabled. If either of these bits are not 0, VMRUN will fail
> with VMEXIT_INVALID error code.
> 
> Because of an IBS race condition when disabling IBS, KVM needs to
> indicate when it is in a PreventHostIBS window. Activate the window
> based on whether IBS is currently active or inactive.
> 
> Signed-off-by: Manali Shukla <manali.shukla@amd.com>

Looks good.

Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>