From: Paolo Bonzini <pbonzini@redhat.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>,
Sean Christopherson <seanjc@google.com>
Cc: 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 6/7] KVM: VMX: Check Intel PT related CPUID leaves
Date: Mon, 18 Oct 2021 14:47:45 +0200 [thread overview]
Message-ID: <486f0075-494d-1d84-2d85-1d451496d1f0@redhat.com> (raw)
In-Reply-To: <a7988439-5a4c-3d5a-ea4a-0fad181ad733@intel.com>
On 10/09/21 03:59, Xiaoyao Li wrote:
>>
>> Ugh, looking at the rest of the code, even this isn't sufficient
>> because pt_desc.guest.addr_{a,b} are hardcoded at 4 entries, i.e.
>> running KVM on hardware with >4 entries will lead to buffer
>> overflows.
>
> it's hardcoded to 4 because there is a note of "no processors support
> more than 4 address ranges" in SDM vol.3 Chapter 31.3.1, table
> 31-11
True, but I agree with Sean that it's not pretty.
>> One option would be to bump that to the theoretical max of 15,
>> which doesn't seem too horrible, especially if pt_desc as a whole
>> is allocated on-demand, which it probably should be since it isn't
>> exactly tiny (nor ubiquitous)
>>
>> A different option would be to let userspace define whatever it
>> wants for guest CPUID, and instead cap nr_addr_ranges at
>> min(host.cpuid, guest.cpuid, RTIT_ADDR_RANGE).
This is the safest option.
Paolo
next prev parent reply other threads:[~2021-10-18 12:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-27 7:02 [PATCH v2 0/7] KVM: VMX: PT (processor trace) optimization cleanup and fixes Xiaoyao Li
2021-08-27 7:02 ` [PATCH v2 1/7] KVM: VMX: Restore host's MSR_IA32_RTIT_CTL when it's not zero Xiaoyao Li
2021-08-27 7:02 ` [PATCH v2 2/7] KVM: VMX: Use precomputed vmx->pt_desc.addr_range Xiaoyao Li
2021-08-27 7:02 ` [PATCH v2 3/7] KVM: VMX: Rename pt_desc.addr_range to pt_desc.nr_addr_range Xiaoyao Li
2021-10-18 12:41 ` Paolo Bonzini
2021-08-27 7:02 ` [PATCH v2 4/7] KVM: VMX: RTIT_CTL_BRANCH_EN has no dependency on other CPUID bit Xiaoyao Li
2021-08-27 7:02 ` [PATCH v2 5/7] KVM: VMX: Disallow PT MSRs accessing if PT is not exposed to guest Xiaoyao Li
2021-10-18 12:46 ` Paolo Bonzini
2021-08-27 7:02 ` [PATCH v2 6/7] KVM: VMX: Check Intel PT related CPUID leaves Xiaoyao Li
2021-09-09 21:41 ` Sean Christopherson
2021-09-10 1:59 ` Xiaoyao Li
2021-10-18 7:01 ` Xiaoyao Li
2021-10-18 12:47 ` Paolo Bonzini [this message]
2021-10-18 13:56 ` Xiaoyao Li
2021-10-18 17:26 ` Sean Christopherson
2021-10-19 1:46 ` Xiaoyao Li
2021-08-27 7:02 ` [PATCH v2 7/7] KVM: VMX: Only context switch some PT MSRs when they exist Xiaoyao Li
2021-10-18 13:08 ` Paolo Bonzini
2021-10-18 14:04 ` Xiaoyao Li
2021-10-18 15:20 ` Paolo Bonzini
2021-10-19 16:52 ` [PATCH v2 0/7] KVM: VMX: PT (processor trace) optimization cleanup and fixes Paolo Bonzini
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