From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: Like Xu <like.xu.linux@gmail.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Like Xu <likexu@tencent.com>
Subject: Re: [PATCH v2 1/6] KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs
Date: Thu, 9 Dec 2021 19:57:23 +0100 [thread overview]
Message-ID: <81fe9f7a-79d5-a77a-089d-99a3b89d78fb@redhat.com> (raw)
In-Reply-To: <CALMp9eR-eniyvu_zsqUHidoDX9V=eAA2zJXKPHdUT6SOY+EQrA@mail.gmail.com>
On 12/9/21 19:53, Jim Mattson wrote:
>> How do we know that i < size? For example, Ice Lake supports 4 fixed
>> counters, but fixed_pmc_events only has three entries.
>
> We don't, and it's a preexisting bug in intel_pmu_refresh.
> As Like points out, KVM_GET_SUPPORTED_CPUID indicates that only three
> fixed counters are supported. So, per the KVM contract, if userspace
> configures four in the guest cpuid info, all bets are off.
Out of bounds accesses are not part of the contract though, even if
squashed by an unorthodox use of array_index_nospec. So I'll post my hack.
> I don't like that contract, but changing it means introducing KVM_SET_CPUID3.
And especially it means getting it right, which is the difficult part.
Paolo
next prev parent reply other threads:[~2021-12-09 18:57 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 7:42 [PATCH v2 0/6] KVM: x86/pmu: Count two basic events for emulated instructions Like Xu
2021-11-30 7:42 ` [PATCH v2 1/6] KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs Like Xu
2021-12-06 19:57 ` Jim Mattson
2021-12-09 18:49 ` Paolo Bonzini
2021-12-09 18:53 ` Jim Mattson
2021-12-09 18:57 ` Paolo Bonzini [this message]
2021-12-10 10:20 ` Like Xu
[not found] ` <CALMp9eTq8H_bJOVKwi_7j3Kum9RvW6o-G3zCLUFco1A1cvNrkQ@mail.gmail.com>
2021-12-07 6:07 ` Like Xu
2021-12-07 17:42 ` Jim Mattson
2021-11-30 7:42 ` [PATCH v2 2/6] KVM: x86/pmu: Refactoring find_arch_event() to pmc_perf_hw_id() Like Xu
2021-12-09 3:52 ` Jim Mattson
2021-12-09 8:11 ` Like Xu
2021-12-09 19:24 ` Paolo Bonzini
2022-02-05 1:55 ` Jim Mattson
2022-02-09 9:00 ` Like Xu
2022-02-09 19:30 ` Jim Mattson
2022-02-10 11:28 ` Like Xu
2022-02-11 9:56 ` Ravi Bangoria
2022-02-11 18:16 ` Jim Mattson
2022-02-14 10:14 ` Ravi Bangoria
2022-02-16 7:44 ` Like Xu
2022-02-16 11:24 ` Ravi Bangoria
2021-11-30 7:42 ` [PATCH v2 3/6] KVM: x86/pmu: Reuse pmc_perf_hw_id() and drop find_fixed_event() Like Xu
2021-12-09 3:58 ` Jim Mattson
2021-11-30 7:42 ` [PATCH v2 4/6] KVM: x86/pmu: Add pmc->intr to refactor kvm_perf_overflow{_intr}() Like Xu
2021-12-09 4:25 ` Jim Mattson
2021-12-09 8:28 ` Like Xu
2021-12-10 0:54 ` Jim Mattson
2021-12-10 9:35 ` Paolo Bonzini
2021-12-10 10:11 ` Like Xu
2021-12-10 22:55 ` Jim Mattson
2021-12-10 22:59 ` Paolo Bonzini
2021-12-10 23:31 ` Jim Mattson
2021-12-12 4:56 ` Jim Mattson
2021-12-13 6:37 ` Jim Mattson
2021-12-16 9:57 ` Like Xu
2021-12-16 17:52 ` Jim Mattson
2021-11-30 7:42 ` [PATCH v2 5/6] KVM: x86: Update vPMCs when retiring instructions Like Xu
2021-12-09 4:33 ` Jim Mattson
2021-12-09 8:44 ` Like Xu
2021-12-09 9:23 ` Like Xu
2021-11-30 7:42 ` [PATCH v2 6/6] KVM: x86: Update vPMCs when retiring branch instructions Like Xu
2021-12-09 4:40 ` Jim Mattson
2021-12-09 19:30 ` [PATCH v2 0/6] KVM: x86/pmu: Count two basic events for emulated instructions Paolo Bonzini
2021-12-16 10:14 ` Like Xu
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