linux-kernel - Re: [PATCH v2 RESEND] x86/asm: Force native_apic_mem

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Message-ID: <81950d38-4d5a-6902-bc2e-327d2800eb58@amd.com>
Date:   Wed, 5 Oct 2022 08:28:56 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "H. Peter Anvin" <hpa@...or.com>,
        Adam Dunlap <acdunlap@...gle.com>,
        Peter Gonda <pgonda@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ben Dooks <ben-linux@...ff.org>,
        LKML <linux-kernel@...r.kernel.org>, llvm@...ts.linux.dev,
        Jacob Xu <jacobhxu@...gle.com>,
        Alper Gun <alpergun@...gle.com>, Marc Orr <marcorr@...gle.com>
Subject: Re: [PATCH v2 RESEND] x86/asm: Force native_apic_mem_read to use mov

On 10/3/22 18:11, H. Peter Anvin wrote:
> On October 3, 2022 4:01:01 PM PDT, Adam Dunlap <acdunlap@...gle.com> wrote:
>> Thanks for all the responses. Is the consensus that we should use the
>> readl function here or instead use inline assembly directly as in the patch
>> I originally sent out:
>>
>> asm_inline("movl %1, %0" : "=r"(out) : "m"(*addr));
>>
>> ? The readl function has this exact same code, I'm just not sure
>> which version fits better stylistically.
> 
> Is mov with an arbitrary addressing mode still acceptable for whatever is causing this problem?

The acceptable forms of MOV are covered by insn_decode_mmio() in 
arch/x86/lib/insn-eval.c.

Thanks,
Tom