From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH] selftests: kvm: fix sync_regs_test with newer gccs
Date: Wed, 9 Oct 2019 09:22:31 -0700 [thread overview]
Message-ID: <20191009162230.GA31986@linux.intel.com> (raw)
In-Reply-To: <5b1b95e5-4836-ab55-fe4d-e9cc78a7a95e@redhat.com>
On Wed, Oct 09, 2019 at 01:11:24PM +0200, Paolo Bonzini wrote:
> On 09/10/19 12:42, Vitaly Kuznetsov wrote:
> > Paolo Bonzini <pbonzini@redhat.com> writes:
> >> There is no practical difference with Vitaly's patch. The first
> >> _vcpu_run has no pre-/post-conditions on the value of %rbx:
> >
> > I think what Sean was suggesting is to prevent GCC from inserting
> > anything (and thus clobbering RBX) between the call to guest_call() and
> > the beginning of 'asm volatile' block by calling *inside* 'asm volatile'
> > block instead.
>
> Yes, but there is no way that clobbering RBX will break the test,
> because RBX is not initialized until after the first _vcpu_run succeeds.
Ah, nice, wasn't aware of that.
prev parent reply other threads:[~2019-10-09 16:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 18:08 [PATCH] selftests: kvm: fix sync_regs_test with newer gccs Vitaly Kuznetsov
2019-10-08 18:29 ` Jim Mattson
2019-10-08 18:40 ` Sean Christopherson
2019-10-08 18:36 ` Sean Christopherson
2019-10-09 9:42 ` Paolo Bonzini
2019-10-09 10:42 ` Vitaly Kuznetsov
2019-10-09 11:11 ` Paolo Bonzini
2019-10-09 12:29 ` Vitaly Kuznetsov
2019-10-09 16:22 ` Sean Christopherson [this message]
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