Messages in this thread | | | Date | Fri, 31 Mar 2023 14:39:26 +0800 | Subject | Re: [RFC PATCH 0/7] SVM guest shadow stack support | From | "Yang, Weijiang" <> |
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On 3/31/2023 4:05 AM, Sean Christopherson wrote: > On Thu, Mar 30, 2023, John Allen wrote: >> On Thu, Mar 30, 2023 at 01:37:38PM +0800, Yang, Weijiang wrote: >>> On 3/29/2023 8:16 AM, Yang, Weijiang wrote: >>>>> Now that the baremetal series has been accepted, how do we want to >>>>> proceed? I think I'd like to send a refreshed version based on the >>>>> version that was accpeted, but I'd want to wait to base it on a new >>>>> version of Weijiang's kvm/vmx series (if one is planned). >>> Patch 1/7 did what I wanted to implement to support AMD SHSTK, my next >>> version will continue refactoring them in vmx scope, then� your series may >>> pick up the helper and modify accordingly. >>> >>> Please note, in my series, I removed check for MSR_IA32_PL{0,1,2}_SSP since >>> they're not supported right now, but your series supports for the MSRs, so >>> you have to change the helper a bit to adapt to your patches. >> The reason we decided to include the PL{0,1,2}_SSP MSRs is that even >> though linux doesn't support supervisor shadow stack, a non-linux guest >> OS might support it and could make use of the MSRs. It could be >> something the vmx patches might want to account for as well > And emulating/virtualizing those MSRs is mandatory unless KVM can hide those MSRs > without violating the architecture (been a while since I looked at CET). If the > architecture does allow enumerating support for userspace but not supervisor, then > ideally the two would be enabled separately in KVM, e.g. so that that if one is > completely busted, we might be able to precisely revert only the broken code.
OK, I'll add a separate patch to expose these supervisor MSRs but they are not accessible on Intel
platform right now, i.e., resulting into #GP.
Meanwhile CPUID(7,1).EDX.bit 18 is always cleared to tell guest supervisor SHSTK is not supported.
Allen can modify per AMD needs.
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