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

[Jan Beulich <jbeulich@suse.com>]

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@suse.com>
>> ---
>> 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