2022-09-06 20:58:13

by Peter Zijlstra

Subject: Re: [PATCH] x86/cpu: Avoid writing MSR_IA32_TSX_CTRL when writing it is not supported

On Tue, Sep 06, 2022 at 10:17:43PM +0200, Hans de Goede wrote:
> On an Intel Atom N2600 (and presumable other Cedar Trail models)
> MSR_IA32_TSX_CTRL can be read, causing saved_msr.valid to be set for it
> by msr_build_context().
>
> This causes restore_processor_state() to try and restore it, but writing
> this MSR is not allowed on the Intel Atom N2600 leading to:

FWIW, virt tends to do this same thing a lot. They'll allow reading
random MSRs and only fail on write.

2022-09-06 21:28:32

by Hans de Goede

Subject: Re: [PATCH] x86/cpu: Avoid writing MSR_IA32_TSX_CTRL when writing it is not supported

Hi,

On 9/6/22 22:43, Peter Zijlstra wrote:
> On Tue, Sep 06, 2022 at 10:17:43PM +0200, Hans de Goede wrote:
>> On an Intel Atom N2600 (and presumable other Cedar Trail models)
>> MSR_IA32_TSX_CTRL can be read, causing saved_msr.valid to be set for it
>> by msr_build_context().
>>
>> This causes restore_processor_state() to try and restore it, but writing
>> this MSR is not allowed on the Intel Atom N2600 leading to:
>
> FWIW, virt tends to do this same thing a lot. They'll allow reading
> random MSRs and only fail on write.

Right. So I guess I should send a v2 with an updated commit
message mentioning this ?

Regards,

Hans