From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BF7018DB02; Fri, 25 Apr 2025 20:14:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745612044; cv=none; b=sp91BArNqj6Phs9RWqq1MVLvwgfgUHUJ4KqFkOmKpLEUbAkITnWByLNJz6YiCTxjKGE6I4buakGEE1x8oO6XJPBHsI4wk6rE/QETq/FCSmm1Q7SUHYpkr45s6xS2nvM0Kv81p/v0i0NfL8yLNeVqeBUVx92rAgrwNj6eKEJmii0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745612044; c=relaxed/simple; bh=Pgn/TZ1ujuuwbnzguLrmQLLDyPec5k7g882M+f0Gsi8=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=M9+r+P3gfZZetmZPbQhgWB/kwEhQGCGOHh6DMLbBvuv28JJuzmumxl9PNeMdB0spGiXuGhjl55np4YEU91C1+fiudletsi2dNvqfI4/I0LQHK7DAkDRM+XiIbBUTghzGQUMTt+PIEkszl1ft79YZ0NKgeLvpx8STCVscfwmNI/g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=LoudM2O5; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="LoudM2O5" Received: from [127.0.0.1] ([76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 53PKCYWU3252234 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 25 Apr 2025 13:12:35 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 53PKCYWU3252234 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025042001; t=1745611957; bh=Pgn/TZ1ujuuwbnzguLrmQLLDyPec5k7g882M+f0Gsi8=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=LoudM2O5Ggb8UKAE6BloQQgcPc3DDE93Uie4tiM2kEIfkYTDiUipcf8Neu/KvASRD bE9VD4R7oFqzmvtHTCFXcREprEax191bGlgx7zIbx5omdo51jLm5RkfhQX4yDbIVRa GVL5VijALlpGtEZskIkKxZJvEBt7FnMylbJIzjd/5nwjnzxaNo83Yy1fNK7XF6PF8t DnRu+iOKDqlUdSjj+DZ7GCvEpBZIZH9XdMoGw1VbkegsrdCwgEQlt1Pl2oarHuisPj gl4+pko/7dDkS+MuVeY76Vou/tfvTznub+Ylyb0SFF25MRCp2uGdpU5pdOUWL4jNE7 1qvVj2z6FqDTA== Date: Fri, 25 Apr 2025 13:12:33 -0700 From: "H. Peter Anvin" To: =?ISO-8859-1?Q?J=FCrgen_Gro=DF?= , Peter Zijlstra CC: Xin Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-pm@vger.kernel.org, linux-edac@vger.kernel.org, xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org, linux-hwmon@vger.kernel.org, netdev@vger.kernel.org, platform-driver-x86@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, acme@kernel.org, andrew.cooper3@citrix.com, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, wei.liu@kernel.org, ajay.kaher@broadcom.com, bcm-kernel-feedback-list@broadcom.com, tony.luck@intel.com, pbonzini@redhat.com, vkuznets@redhat.com, seanjc@google.com, luto@kernel.org, boris.ostrovsky@oracle.com, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com Subject: =?US-ASCII?Q?Re=3A_=5BRFC_PATCH_v2_21/34=5D_x86/msr=3A_Utiliz?= =?US-ASCII?Q?e_the_alternatives_mechanism_to_write_MSR?= User-Agent: K-9 Mail for Android In-Reply-To: <35979102-2eb2-4566-b32a-f2b02ded8ae6@suse.com> References: <20250422082216.1954310-1-xin@zytor.com> <20250422082216.1954310-22-xin@zytor.com> <37c88ea3-dd24-4607-9ee1-0f19025aaef3@suse.com> <20250425123317.GB22125@noisy.programming.kicks-ass.net> <35979102-2eb2-4566-b32a-f2b02ded8ae6@suse.com> Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On April 25, 2025 5:51:27 AM PDT, "J=C3=BCrgen Gro=C3=9F" wrote: >On 25=2E04=2E25 14:33, Peter Zijlstra wrote: >> On Wed, Apr 23, 2025 at 06:05:19PM +0200, J=C3=BCrgen Gro=C3=9F wrote: >>=20 >>>> It's not a major change, but when it is patched to use the immediate >>>> form MSR write instruction, it's straightforwardly streamlined=2E >>>=20 >>> It should be rather easy to switch the current wrmsr/rdmsr paravirt pa= tching >>> locations to use the rdmsr/wrmsr instructions instead of doing a call = to >>> native_*msr()=2E >>=20 >> Right, just make the Xen functions asm stubs that expect the instructio= n >> registers instead of C-abi and ALT_NOT_XEN the thing=2E >>=20 >> Shouldn't be hard at all=2E > >Correct=2E And for the new immediate form we can use ALTERNATIVE_3()=2E > > >Juergen Yes; in the ultimate case there are *four* alternatives, but the concept i= s the same and again we have it implemented already=2E