Re: [Xen-devel] [PATCH v4] x86/AMD: Add support for AMD's OSVW feature in guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.02.12 at 21:29, Boris Ostrovsky <boris.ostrovsky@xxxxxxx> wrote:
> On 02/02/12 08:22, Jan Beulich wrote:
>> As I was about to apply this to my local tree to give it a try, I had
>> to realize that the microcode integration is still not correct: There
>> is (at least from an abstract perspective) no guarantee for
>> cpu_request_microcode() to be called on all CPUs, yet you want
>> svm_host_osvw_init() to be re-run on all of them. If you choose
>> to not deal with this in a formally correct way, it should be stated
>> so in a code comment (to lower the risk of surprises when someone
>> touches that code) that this is not possible in practice because
>> collect_cpu_info() won't currently fail for CPUs of interest.
> 
> What if svm_host_osvw_init() is called from collect_cpu_info()? There 
> may be cases when svm_host_osvw_init() is called multiple times for the 
> same cpu but that should be harmless (and the routine will be renamed to 
> svm_host_osvw_update()).

Wouldn't that result in workaround bits that might get cleared with
the pending microcode update to get (and remain) set, as they're
being or-ed together over all invocations of the function after any
svm_host_osvw_reset()?

Jan


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