On Wed, Feb 23, 2022 at 05:31:53PM +0100, Jan Beulich wrote:
> On 23.02.2022 17:11, Roger Pau Monné wrote:
> > On Wed, Feb 23, 2022 at 09:38:56AM -0600, Alex Olson wrote:
> >> 1) For conditions in which MSR registers are writeable from PV guests
> >> (such as
> >> dom0), they should probably be r
On 23.02.2022 17:11, Roger Pau Monné wrote:
> On Wed, Feb 23, 2022 at 09:38:56AM -0600, Alex Olson wrote:
>> 1) For conditions in which MSR registers are writeable from PV guests (such
>> as
>> dom0), they should probably be readable well, looks like
>> MSR_IA32_THERM_CONTROL
>> is currently one
On 23.02.2022 16:38, Alex Olson wrote:
> It seems to me there are a few findings useful to the Xen developers from
> venturing down this rabbithole:
>
> 1) For conditions in which MSR registers are writeable from PV guests (such as
> dom0), they should probably be readable well, looks like
> MSR
On Wed, Feb 23, 2022 at 09:38:56AM -0600, Alex Olson wrote:
> I appreciate your interest, apologies for not replying right away. I've been
> digging deeper to have a more meaningful resposne.
>
> I had attempted to instrument the MSR reads, but only saw a small number reads
> being blocked by the
Hi Roger,
See my other reply which is more detailed. While enabling reads of
"MSR_IA32_ENERGY_PERF_BIAS" did not cause any effect in my case, it is one of a
handful of exceptions in which MSRs are writeable but not readable. I believe
this may result in potentially unexpected behavior in read-ch
I appreciate your interest, apologies for not replying right away. I've been
digging deeper to have a more meaningful resposne.
I had attempted to instrument the MSR reads, but only saw a small number reads
being blocked by the code change. They appear to be the list below and the
others seem fair
On Thu, Feb 10, 2022 at 11:27:15AM -0600, Alex Olson wrote:
> I'm seeing strange performance issues under Xen on a Supermicro server with a
> Xeon D-1541 CPU caused by an MSR-related commit.
>
> Commit 322ec7c89f6640ee2a99d1040b6f786cf04872cf 'x86/pv: disallow access to
> unknown MSRs'
> surpris
On 10/02/2022 17:27, Alex Olson wrote:
> I'm seeing strange performance issues under Xen on a Supermicro server with a
> Xeon D-1541 CPU caused by an MSR-related commit.
>
> Commit 322ec7c89f6640ee2a99d1040b6f786cf04872cf 'x86/pv: disallow access to
> unknown MSRs'
> surprisingly introduces a sev
I'm seeing strange performance issues under Xen on a Supermicro server with a
Xeon D-1541 CPU caused by an MSR-related commit.
Commit 322ec7c89f6640ee2a99d1040b6f786cf04872cf 'x86/pv: disallow access to
unknown MSRs'
surprisingly introduces a severe performance penality where dom0 has about 1/8t
