Re: [PATCH 00/32] x86/msr: Drop 32-bit MSR interfaces

[Jan Beulich <jbeulich@xxxxxxxx>]

On 29.06.2026 10:15, Jürgen Groß wrote:
> On 29.06.26 10:06, Arnd Bergmann wrote:
>> On Mon, Jun 29, 2026, at 09:01, Jürgen Groß wrote:
>>> On 29.06.26 08:52, Arnd Bergmann wrote:
>>>> On Mon, Jun 29, 2026, at 08:04, Juergen Gross wrote:
>>>>
>>>> I assume this is fine, but since you don't mention it explicitly here,
>>>> please clarify what this means for 32-bit CPUs without the rdmsrq
>>>> instruction. Those will continue using the same instructions as before
>>>> and just change the calling conventions, right?
>>>
>>> Yes. I thought this would be clear from the following:
>>>
>>>     - They are based on primitives using 64-bit sized values anyway.
>>
>> Right, that was my reading of it as well, but it's not entirely
>> clear when the function name is the same as the mnemonic of an
>> instruction that only exists on newer CPUs and the later patch
> 
> There is no RDMSRQ instruction on any x86 CPU.

And perhaps wrongly so. On the binutils side I did argue previously that it
is in the spirit of the original AT&T assembler language to permit, but not
require, suffixes matching the size of (uniform) register operands. Even for
insns not allowing for memory operands, simply for overall consistency.

(I took the liberty to at least limit the number of Cc-ed lists some.)

Jan