Re: [RFC PATCH v2 21/34] x86/msr: Utilize the alternatives mechanism to write MSR

Jürgen Groß
2025-04-25T12:51:31Z

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On 25.04.25 14:33, Peter Zijlstra wrote:
> On Wed, Apr 23, 2025 at 06:05:19PM +0200, Jürgen Groß wrote:
>
>>> It's not a major change, but when it is patched to use the immediate
>>> form MSR write instruction, it's straightforwardly streamlined.
>>
>> It should be rather easy to switch the current wrmsr/rdmsr paravirt patching
>> locations to use the rdmsr/wrmsr instructions instead of doing a call to
>> native_*msr().
>
> Right, just make the Xen functions asm stubs that expect the instruction
> registers instead of C-abi and ALT_NOT_XEN the thing.
>
> Shouldn't be hard at all.

Correct. And for the new immediate form we can use ALTERNATIVE_3().

Juergen

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