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

[Christoph Egger <Christoph.Egger@amd.com>]

On 01/31/12 11:13, Jan Beulich wrote:
>> --- a/xen/arch/x86/platform_hypercall.c	Thu Jan 26 17:43:31 2012 +0000
>> +++ b/xen/arch/x86/platform_hypercall.c	Mon Jan 30 18:00:50 2012 +0100
>> @@ -166,7 +166,17 @@ ret_t do_platform_op(XEN_GUEST_HANDLE(xe
>>               break;
>>
>>           guest_from_compat_handle(data, op->u.microcode.data);
>> +
>> +        while ( !domctl_lock_acquire() )
>
> It's not clear to me what you're trying to protect against here. I don't
> think this prevents guests from making progress (and hence possibly
> seeing the intermediate [and wrong] OSVW state between
> svm_host_osvw_reset() and svm_host_osvw_init()).

The reason is because when we allocated VCPUs (via XEN_DOMCTL_max_vcpus 
and possibly other controls) we call svm_vcpu_initialise() -> 
svm_guest_osvw_init(). If we are in the middle of microcode update then 
osvw_length/osvw_status may be in an inconsistent state.

Christoph

> Jan
>
>> +            if ( hypercall_preempt_check() )
>> +            {
>> +                ret = hypercall_create_continuation(
>> +                    __HYPERVISOR_platform_op, "h", u_xenpf_op);
>> +                goto out;
>> +            }
>> +
>>           ret = microcode_update(data, op->u.microcode.length);
>> +        domctl_lock_release();
>>       }
>>       break;
>>
>
>
>


-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Einsteinring 24, 85689 Dornach b. Muenchen
Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632