From: Andrew Cooper <andrew.cooper3@citrix.com>
To: jgross@suse.com
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com,
peterz@infradead.org, tglx@kernel.org, x86@kernel.org,
xin@zytor.com
Subject: Re: [PATCH v3 08/16] x86/extable: Add support for immediate form MSR instructions
Date: Wed, 18 Feb 2026 15:48:07 +0000 [thread overview]
Message-ID: <7135fe16-25eb-44c2-9b5d-99f4cecea3dc@citrix.com> (raw)
In-Reply-To: <20260218082133.400602-9-jgross@suse.com>
Ideally please CC xen-devel on all patches if you've CC'd some, or at
least CC me on all patches that you partially send to xen-devel. Having
only 4 patches of the series is very awkward to reply to.
> + /* + * To maintain consistency with existing RDMSR and WRMSR(NS)
> instructions, + * the register operand for immediate form MSR
> instructions is ALWAYS + * encoded as RAX in <asm/msr.h> for reading
> or writing the MSR value. + */ + u64 msr_val = regs->ax;
This is unsafe. It assumes that the only source of MSR $IMM
instructions anywhere are the wrappers.
While this might be the wish of the developers, that doesn't make it true.
You've already decoded the instruction and got the ModRM byte, so either
check that it really is encoding %rax, or select the proper GPR based on
ModRM.
~Andrew
next prev parent reply other threads:[~2026-02-18 15:48 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 [this message]
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
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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