linux-kernel - RE: [PATCH] KVM/VMX: Do not declare vmread

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Message-ID: <CY5PR11MB636505ECC6D27486065E5CE0DC7E9@CY5PR11MB6365.namprd11.prod.outlook.com>
Date:   Tue, 6 Sep 2022 07:28:22 +0000
From:   "Wang, Wei W" <wei.w.wang@...el.com>
To:     "Christopherson,, Sean" <seanjc@...gle.com>,
        Uros Bizjak <ubizjak@...il.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: RE: [PATCH] KVM/VMX: Do not declare vmread_error asmlinkage

On Thursday, September 1, 2022 11:37 PM, Sean Christopherson wrote:
> > > And vmread_error() isn't the only case where asmlinkage appears to be a
> burden, e.g.
> > > schedule_tail_wrapper() => schedule_tail() seems to exist purely to
> > > deal with the side affect of asmlinkage generating -regparm=0 on 32-bit
> kernels.
> >
> > schedule_tail is external to the x86 arch directory, and for some
> > reason marked asmlinkage. So, the call from asm must follow asmlinkage
> > ABI.
> 
> Ahhh, it's a common helper that's called from assembly on other architectures.
> That makes sense.

I still doubt the necessity. The compilation is architecture specific, and we don't
build one architecture-agnostic kernel binary to run on different architectures,
right?

Thanks,
Wei