From: Dave Hansen <dave.hansen@intel.com>
To: Sean Christopherson <seanjc@google.com>, Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
kvm@vger.kernel.org, llvm@lists.linux.dev, Xin Li <xin@zytor.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>
Subject: Re: [PATCH v3 09/16] x86/msr: Use the alternatives mechanism for WRMSR
Date: Wed, 18 Feb 2026 13:37:42 -0800 [thread overview]
Message-ID: <e05a65a7-bf8e-420b-8a36-2d76e56b43b0@intel.com> (raw)
In-Reply-To: <aZYoUE7CmrLg3SVe@google.com>
On 2/18/26 13:00, Sean Christopherson wrote:
> On Wed, Feb 18, 2026, Juergen Gross wrote:
>> When available use one of the non-serializing WRMSR variants (WRMSRNS
>> with or without an immediate operand specifying the MSR register) in
>> __wrmsrq().
> Silently using a non-serializing version (or not) seems dangerous (not for KVM,
> but for the kernel at-large), unless the rule is going to be that MSR writes need
> to be treated as non-serializing by default.
Yeah, there's no way we can do this in general. It'll work for 99% of
the MSRs on 99% of the systems for a long time. Then the one new system
with WRMSRNS is going to have one hell of a heisenbug that'll take years
off some poor schmuck's life.
We should really encourage *new* code to use wrmsrns() when it can at
least for annotation that it doesn't need serialization. But I don't
think we should do anything to old, working code.
next prev parent reply other threads:[~2026-02-18 21:37 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-18 8:21 [PATCH v3 00/16] x86/msr: Inline rdmsr/wrmsr instructions Juergen Gross
2026-02-18 8:21 ` [PATCH v3 01/16] x86/alternative: Support alt_replace_call() with instructions after call Juergen Gross
2026-04-02 13:58 ` Juergen Gross
2026-02-18 8:21 ` [PATCH v3 02/16] coco/tdx: Rename MSR access helpers Juergen Gross
2026-02-18 14:11 ` Edgecombe, Rick P
2026-02-18 8:21 ` [PATCH v3 03/16] x86/sev: Replace call of native_wrmsr() with native_wrmsrq() Juergen Gross
2026-02-18 8:21 ` [PATCH v3 04/16] KVM: x86: Remove the KVM private read_msr() function Juergen Gross
2026-02-18 14:21 ` Edgecombe, Rick P
2026-02-18 14:29 ` Sean Christopherson
2026-02-18 8:21 ` [PATCH v3 05/16] x86/msr: Minimize usage of native_*() msr access functions Juergen Gross
2026-02-18 8:21 ` [PATCH v3 06/16] x86/msr: Move MSR trace calls one function level up Juergen Gross
2026-02-18 8:21 ` [PATCH v3 07/16] x86/opcode: Add immediate form MSR instructions Juergen Gross
2026-02-18 8:21 ` [PATCH v3 08/16] x86/extable: Add support for " Juergen Gross
2026-02-18 15:48 ` Andrew Cooper
2026-02-18 16:28 ` Jürgen Groß
2026-02-18 8:21 ` [PATCH v3 09/16] x86/msr: Use the alternatives mechanism for WRMSR Juergen Gross
2026-02-18 21:00 ` Sean Christopherson
2026-02-18 21:37 ` Dave Hansen [this message]
2026-02-18 23:36 ` H. Peter Anvin
2026-02-19 6:41 ` Jürgen Groß
2026-02-19 6:44 ` Jürgen Groß
2026-02-20 17:12 ` Xin Li
2026-02-20 17:32 ` Sean Christopherson
2026-02-20 17:40 ` Dave Hansen
2026-02-23 17:56 ` Xin Li
2026-02-23 21:34 ` H. Peter Anvin
2026-02-18 8:21 ` [PATCH v3 10/16] x86/msr: Use the alternatives mechanism for RDMSR Juergen Gross
2026-02-18 15:12 ` kernel test robot
2026-02-18 15:48 ` Juergen Gross
2026-02-18 8:21 ` [PATCH v3 11/16] x86/alternatives: Add ALTERNATIVE_4() Juergen Gross
2026-02-18 8:21 ` [PATCH v3 12/16] x86/paravirt: Split off MSR related hooks into new header Juergen Gross
2026-02-18 8:21 ` [PATCH v3 13/16] x86/paravirt: Prepare support of MSR instruction interfaces Juergen Gross
2026-02-18 8:21 ` [PATCH v3 14/16] x86/paravirt: Switch MSR access pv_ops functions to " Juergen Gross
2026-02-18 8:21 ` [PATCH v3 15/16] x86/msr: Reduce number of low level MSR access helpers Juergen Gross
2026-02-18 8:21 ` [PATCH v3 16/16] x86/paravirt: Use alternatives for MSR access with paravirt Juergen Gross
2026-02-18 13:49 ` kernel test robot
2026-02-18 15:49 ` Juergen Gross
2026-02-18 20:37 ` [PATCH v3 00/16] x86/msr: Inline rdmsr/wrmsr instructions H. Peter Anvin
2026-02-19 6:28 ` Jürgen Groß
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