linux-kernel - Re: [PATCH] KVM: selftests: restore special vmmcall code layout needed by the harness

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

Sean Christopherson <seanjc@...gle.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@...hat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.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@...gle.com>
>

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

-- 
Vitaly