Messages in this thread | | | Date | Tue, 23 Jun 2020 13:30:07 +0200 | From | Joerg Roedel <> | Subject | Re: Should SEV-ES #VC use IST? (Re: [PATCH] Allow RDTSC and RDTSCP from userspace) |
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On Tue, Jun 23, 2020 at 01:07:06PM +0200, Peter Zijlstra wrote: > On Tue, Apr 28, 2020 at 09:55:12AM +0200, Joerg Roedel wrote:
> So what happens if this #VC triggers on the first access to the #VC > stack, because the malicious host has craftily mucked with only the #VC > IST stack page? > > Or on the NMI IST stack, then we get #VC in NMI before the NMI can fix > you up. > > AFAICT all of that is non-recoverable.
I am not 100% sure, but I think if the #VC stack page is not validated, the #VC should be promoted to a #DF.
Note that this is an issue only with secure nested paging (SNP), which is not enabled yet with this patch-set. When it gets enabled a stack recursion check in the #VC handler is needed which panics the VM. That also fixes the #VC-in-early-NMI problem.
Regards,
Joerg
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