From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH 2/2] x86/hvm: Don't intercept #UD exceptions
	in general
Date: Wed, 27 Jan 2016 14:14:24 -0500
Message-ID: <56A91710.7010701@oracle.com>
References: <1453918273-23008-1-git-send-email-andrew.cooper3@citrix.com>
	<1453918273-23008-2-git-send-email-andrew.cooper3@citrix.com>
	<56A91122.50502@oracle.com> <56A91390.4030604@citrix.com>
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To: Andrew Cooper <andrew.cooper3@citrix.com>, Xen-devel <xen-devel@lists.xen.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>, Kevin Tian <kevin.tian@intel.com>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Jun Nakajima <jun.nakajima@intel.com>, Jan Beulich <JBeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 01/27/2016 01:59 PM, Andrew Cooper wrote:
> On 27/01/16 18:49, Boris Ostrovsky wrote:
>> On 01/27/2016 01:11 PM, Andrew Cooper wrote:
>>> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
>>> index 1d71216..1084e82 100644
>>> --- a/xen/arch/x86/domctl.c
>>> +++ b/xen/arch/x86/domctl.c
>>> @@ -65,8 +65,20 @@ static void update_domain_cpuid_info(struct domain
>>> *d,
>>>                    .ecx = ctl->ecx
>>>                }
>>>            };
>>> +        int old_vendor = d->arch.x86_vendor;
>>>              d->arch.x86_vendor = get_cpu_vendor(vendor_id.str,
>>> gcv_guest);
>>> +
>>> +        if ( is_hvm_domain(d) && (d->arch.x86_vendor != old_vendor) )
>>> +        {
>>> +            struct vcpu *v;
>>> +
>>> +            domain_pause(d);
>>> +            for_each_vcpu( d, v )
>>> +                hvm_update_guest_vendor(v);
>>> +            domain_unpause(d);
>>> +        }
>>> +
>>>            break;
>>>        }
>> Not specific to this patch, but shouldn't we pause/unpause domain for
>> the whole routine?
> Not specifically, although that might be better lonterm.
>
> In practice, this hypercall is only made as part of domain construction,
> and never at domain runtime.

Is it safe to unpause a domain here if it is not running?

-boris