linux-kernel - Re: [PATCH] KVM: selftests: Double check on the current CPU in rseq

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Message-ID: <a2ade925-89db-5d05-ba44-e3b77125032e@redhat.com>
Date:   Thu, 14 Jul 2022 17:42:22 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Gavin Shan <gshan@...hat.com>, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        shuah@...nel.org, maz@...nel.org, oliver.upton@...ux.dev,
        shan.gavin@...il.com
Subject: Re: [PATCH] KVM: selftests: Double check on the current CPU in
 rseq_test

On 7/14/22 17:35, Sean Christopherson wrote:
>> Can you check that smp_rmb() and smp_wmb() generate correct instructions on
>> arm64?
> 
> That seems like the most likely scenario (or a kernel bug), I distinctly remember
> the barriers provided by tools/ being rather bizarre.

Maybe we should bite the bait and use C11 atomics in tools/.  I've long 
planned an article "C11 atomics for kernel programmers", especially 
because this will also be an issue when Rust gets into the mix...

Paolo