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X-CSE-ConnectionGUID: tTzk+SnnQpKDDWXbiHU55A== X-CSE-MsgGUID: dGYxyRtURTmqOxfv8r4ttQ== X-IronPort-AV: E=McAfee;i="6700,10204,11323"; a="37993873" X-IronPort-AV: E=Sophos;i="6.13,226,1732608000"; d="scan'208";a="37993873" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jan 2025 16:36:38 -0800 X-CSE-ConnectionGUID: Cs17F97wSD+OhDom8NAC6w== X-CSE-MsgGUID: eXwomfsXTg+Vmotv7MBSAA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,226,1732608000"; d="scan'208";a="107228394" Received: from tfalcon-desk.amr.corp.intel.com (HELO [10.124.222.224]) ([10.124.222.224]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jan 2025 16:36:30 -0800 Message-ID: Date: Wed, 22 Jan 2025 16:36:31 -0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/2] x86, lib: Add WBNOINVD helper functions To: Kevin Loughlin , linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, kirill.shutemov@linux.intel.com, kai.huang@intel.com, ubizjak@gmail.com, jgross@suse.com, kvm@vger.kernel.org, thomas.lendacky@amd.com, pgonda@google.com, sidtelang@google.com, mizhang@google.com, rientjes@google.com, manalinandan@google.com, szy0127@sjtu.edu.cn References: <20250122013438.731416-1-kevinloughlin@google.com> <20250123002422.1632517-1-kevinloughlin@google.com> <20250123002422.1632517-2-kevinloughlin@google.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/22/25 16:24, Kevin Loughlin wrote: > +static __always_inline void wbnoinvd(void) > +{ > + /* > + * WBNOINVD is encoded as 0xf3 0x0f 0x09. Making this > + * encoding explicit ensures compatibility with older versions of > + * binutils, which may not know about WBNOINVD. This kinda pokes at one of my pet peeves. It's writing a comment where code would do. I'd *much* rather write a function that explains to you in code that "WBNOINVD is encoded as 0xf3 0x0f 0x09": static __always_inline void native_wbnoinvd(void) { asm volatile(".byte 0xf3,0x0f,0x09\n\t": : :"memory"); } instead of writing out a comment. It's kinda silly to have to write out the encoding explicitly in a comment and then have to rewrite it in the code.