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Re: [PATCH 1/3] x86/Intel: skip PLATFORM_INFO reads on family 0xf


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 11 Feb 2022 10:59:10 +0100
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
  • Delivery-date: Fri, 11 Feb 2022 09:59:25 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 11.02.2022 10:40, Roger Pau Monné wrote:
> On Thu, Feb 10, 2022 at 03:55:52PM +0100, Jan Beulich wrote:
>> This avoids unnecessary (and always somewhat scary) log messages for the
>> recovered from #GP(0).
> 
> Could we maybe get rid of the #GP messages for cases like this where we
> are explicitly probing for MSR presence? (ie: it's expected that we
> can get a #GP)

This would mean some form of annotation of such RDMSR attempts (for
the recovery code to recognize in order to skip the printk()). Not
all rdmsr_safe() uses are, strictly speaking, probes, so I wouldn't
want to put such in rdmsr_safe() itself.

In any event - quite a bit more work. Plus I'm not convinced it's a
good idea to suppress any such log messages.

>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> ---
>> Perhaps even use "!= 6" in at least the CPUID-faulting family check?
> 
> Likely, or else you would also need to check for family 11 (Knights
> Corner?) which doesn't seem to support PLATFORM_INFO either.

I don't think Xen is able to run on these (likewise for IA64, which
iirc were surfacing as x86 model 7)? These are the co-processor ones,
aren't they? My question was more towards whether we would (wrongly)
exclude future processors when using != 6, if Intel decided to ever
make new CPUs with a family other than 6.

Jan




 


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