From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Egger <Christoph.Egger@amd.com>
Subject: Re: [PATCH] x86/AMD: Add support for AMD's OSVW feature
	in guests
Date: Tue, 31 Jan 2012 11:36:07 +0100
Message-ID: <4F27C417.2070209@amd.com>
References: <1361d9895cb17aa8fce1.1327943146@wotan.osrc.amd.com>
	<4F27CCE40200007800070120@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@amd.com>, xen-devel@lists.xensource.com, keir@xen.org
List-Id: xen-devel@lists.xenproject.org

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;
>>
>
>
>


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