lkml.org 
[lkml]   [2021]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2 6/7] KVM: VMX: Check Intel PT related CPUID leaves
From
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

\
 
 \ /
  Last update: 2021-10-18 14:48    [W:0.136 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site