Messages in this thread | | | Date | Mon, 18 Oct 2021 14:47:45 +0200 | Subject | Re: [PATCH v2 6/7] KVM: VMX: Check Intel PT related CPUID leaves | From | Paolo Bonzini <> |
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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
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