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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: selftests: restore special vmmcall code layout
 needed by the harness
In-Reply-To: <Y4ffgC+HbftkPbaW@google.com>
References: <20221130181147.9911-1-pbonzini@redhat.com>
 <Y4ffgC+HbftkPbaW@google.com>
Date:   Thu, 01 Dec 2022 10:28:51 +0100
Message-ID: <87r0xjh3qk.fsf@ovpn-194-141.brq.redhat.com>
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Sean Christopherson <seanjc@google.com> writes:

> On Wed, Nov 30, 2022, Paolo Bonzini wrote:
>> Commit 8fda37cf3d41 ("KVM: selftests: Stuff RAX/RCX with 'safe' values
>> in vmmcall()/vmcall()", 2022-11-21) broke the svm_nested_soft_inject_test
>> because it placed a "pop rbp" instruction after vmmcall.  While this is
>> correct and mimics what is done in the VMX case, this particular test
>> expects a ud2 instruction right after the vmmcall, so that it can skip
>> over it in the L1 part of the test.
>> 
>> Inline a suitably-modified version of vmmcall() to restore the
>> functionality of the test.
>>
>> Fixes: 8fda37cf3d41 ("KVM: selftests: Stuff RAX/RCX with 'safe' values in vmmcall()/vmcall()"
>> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>
> We really, really need to save/restore guest GPRs in L1 when handling exits from L2.

+1, the amount of stuff we do to workaround the shortcoming (and time
we waste debugging) is getting ridiculously high. 

>
> For now,
>
> Reviewed-by: Sean Christopherson <seanjc@google.com>
>

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly