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Message-ID: <ZMfFaF2M6Vrh/QdW@google.com>
Date: Mon, 31 Jul 2023 07:30:00 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: wuzongyong <wuzongyo@...l.ustc.edu.cn>
Cc: linux-kernel@...r.kernel.org, thomas.lendacky@....com,
kvm@...r.kernel.org, x86@...nel.org, linux-coco@...ts.linux.dev
Subject: Re: [Question] int3 instruction generates a #UD in SEV VM
On Sat, Jul 29, 2023, wuzongyong wrote:
> Hi,
> I am writing a firmware in Rust to support SEV based on project td-shim[1].
> But when I create a SEV VM (just SEV, no SEV-ES and no SEV-SNP) with the firmware,
> the linux kernel crashed because the int3 instruction in int3_selftest() cause a
> #UD.
...
> BTW, if a create a normal VM without SEV by qemu & OVMF, the int3 instruction always generates a
> #BP.
> So I am confused now about the behaviour of int3 instruction, could anyone help to explain the behaviour?
> Any suggestion is appreciated!
Have you tried my suggestions from the other thread[*]?
: > > I'm curious how this happend. I cannot find any condition that would
: > > cause the int3 instruction generate a #UD according to the AMD's spec.
:
: One possibility is that the value from memory that gets executed diverges from the
: value that is read out be the #UD handler, e.g. due to patching (doesn't seem to
: be the case in this test), stale cache/tlb entries, etc.
:
: > > BTW, it worked nomarlly with qemu and ovmf.
: >
: > Does this happen every time you boot the guest with your firmware? What
: > processor are you running on?
:
: And have you ruled out KVM as the culprit? I.e. verified that KVM is NOT injecting
: a #UD. That obviously shouldn't happen, but it should be easy to check via KVM
: tracepoints.
[*] https://lore.kernel.org/all/ZMFd5kkehlkIfnBA@google.com
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