From: Like Xu <like.xu@linux.intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/4] KVM: vmx/pmu: Add MSR_ARCH_LBR_DEPTH emulation for Arch LBR
Date: Tue, 2 Mar 2021 10:52:51 +0800 [thread overview]
Message-ID: <d194f89a-cd56-6f32-4797-ae11956bf5ba@linux.intel.com> (raw)
In-Reply-To: <YD1r2G1UQjVXkUk5@google.com>
On 2021/3/2 6:34, Sean Christopherson wrote:
> On Wed, Feb 03, 2021, Like Xu wrote:
>> @@ -348,10 +352,26 @@ static bool intel_pmu_handle_lbr_msrs_access(struct kvm_vcpu *vcpu,
>> return true;
>> }
>>
>> +/*
>> + * Check if the requested depth values is supported
>> + * based on the bits [0:7] of the guest cpuid.1c.eax.
>> + */
>> +static bool arch_lbr_depth_is_valid(struct kvm_vcpu *vcpu, u64 depth)
>> +{
>> + struct kvm_cpuid_entry2 *best;
>> +
>> + best = kvm_find_cpuid_entry(vcpu, 0x1c, 0);
>> + if (depth && best)
>
>> + return (best->eax & 0xff) & (1ULL << (depth / 8 - 1));
>
> I believe this will genereate undefined behavior if depth > 64. Or if depth < 8.
> And I believe this check also needs to enforce that depth is a multiple of 8.
>
> For each bit n set in this field, the IA32_LBR_DEPTH.DEPTH value 8*(n+1) is
> supported.
>
> Thus it's impossible for 0-7, 9-15, etc... to be legal depths.
Thank you! How about:
best = kvm_find_cpuid_entry(vcpu, 0x1c, 0);
if (best && depth && !(depth % 8))
return (best->eax & 0xff) & (1ULL << (depth / 8 - 1));
return false;
>
>
>> +
>> + return false;
>> +}
>> +
>
next prev parent reply other threads:[~2021-03-02 15:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 13:57 [PATCH v2 0/4] KVM: x86/pmu: Guest Architectural LBR Enabling Like Xu
2021-02-03 13:57 ` [PATCH v2 1/4] KVM: vmx/pmu: Add MSR_ARCH_LBR_DEPTH emulation for Arch LBR Like Xu
2021-03-01 22:34 ` Sean Christopherson
2021-03-02 2:52 ` Like Xu [this message]
2021-02-03 13:57 ` [PATCH v2 2/4] KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL " Like Xu
2021-02-03 13:57 ` [PATCH v2 3/4] KVM: vmx/pmu: Add Arch LBR emulation and its VMCS field Like Xu
2021-02-03 13:57 ` [PATCH v2 4/4] KVM: x86: Expose Architectural LBR CPUID and its XSAVES bit Like Xu
2021-02-03 14:37 ` Paolo Bonzini
2021-02-04 0:59 ` Xu, Like
2021-02-05 8:16 ` Xu, Like
2021-02-05 11:00 ` Paolo Bonzini
2021-02-07 1:02 ` Xu, Like
2021-02-08 10:31 ` Paolo Bonzini
2021-04-14 1:00 ` Xu, Like
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