Re: [kvm-unit-tests PATCH 3/3] x86: Add test coverage for the routing logic when exceptions occur in L2

From: Aaron Lewis <aaronlewis@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com
Subject: Re: [kvm-unit-tests PATCH 3/3] x86: Add test coverage for the routing logic when exceptions occur in L2
Date: Tue, 14 Dec 2021 01:19:00 +0000	[thread overview]
Message-ID: <CAAAPnDH9ghcFid5_b-US6o0eMyLFSCBWXBASbV_PB92srzdO6A@mail.gmail.com> (raw)
In-Reply-To: <YbJx1iB9ZowrVcuF@google.com>

> Having a gigantic asm blob is also unnecessary.  #GP can be generated with a
> non-canonical access purely in C.  Ditto for #AC though that may or may not be
> more readable.  #DE probably requires assembly to avoid compiler intervention.

For #AC I'd prefer to leave this in ASM.  To get this to work in C I
had to trick the compiler to not optimize the code away and when I was
playing with it in compiler explorer clang seemed to outsmart my
unaligning access with an aligned one which defeated the purpose.  It
seems more reliable for what I want to leave it in ASM.

> #UD and #BP should be short and sweet.  E.g.
>
> It should be fairly straightforward to create a framework to handle running each
> test, a la the vmx_tests array.  E.g. something like the below (completely untested).
> This way there's no need to skip instructions, thus no need for a exposing a bunch