Re: [PATCHv5 1/2] x86/ept: invalidate guest physical mappings on VMENTER

From: George Dunlap <george.dunlap@citrix.com>
To: David Vrabel <david.vrabel@citrix.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Jan Beulich <jbeulich@suse.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>
Subject: Re: [PATCHv5 1/2] x86/ept: invalidate guest physical mappings on VMENTER
Date: Fri, 18 Dec 2015 10:24:20 +0000	[thread overview]
Message-ID: <5673DED4.7020707@citrix.com> (raw)
In-Reply-To: <5673DD64.90500@citrix.com>

On 18/12/15 10:18, David Vrabel wrote:
> On 18/12/15 07:53, Tian, Kevin wrote:
>>> From: David Vrabel [mailto:david.vrabel@citrix.com]
>>> Sent: Thursday, December 17, 2015 11:17 PM
>>
>> [...]
>>
>>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>>> index f7c5e4f..cca35f2 100644
>>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>>
>> [...]
>>
>>> @@ -3507,6 +3495,16 @@ void vmx_vmenter_helper(const struct cpu_user_regs *regs)
>>>      if ( unlikely(need_flush) )
>>>          vpid_sync_all();
>>>
>>> +    if ( paging_mode_hap(curr->domain) )
>>> +    {
>>> +        struct ept_data *ept = &p2m_get_hostp2m(curr->domain)->ept;
>>> +        unsigned int cpu = smp_processor_id();
>>> +
>>> +        if ( cpumask_test_cpu(cpu, ept->invalidate)
>>> +             && cpumask_test_and_clear_cpu(cpu, ept->invalidate) )
>>
>> Just test_and_clear should be enough.
> 
> The first test is to avoid the locked test and clear in the common case.
>  But this is probably better written as
> 
>   if ( cpumask_test_cpu(cpu, ept->invalidate) )
>   {
>       cpumask_clear_cpu(cpu, ept->invalidate);
>       __invept(...);
>    }
> 
>>> --- a/xen/arch/x86/mm/p2m-ept.c
>>> +++ b/xen/arch/x86/mm/p2m-ept.c
>>> @@ -1089,9 +1089,10 @@ static void ept_memory_type_changed(struct p2m_domain
>>> *p2m)
>>>
>>>  static void __ept_sync_domain(void *info)
>>>  {
>>> -    struct ept_data *ept = &((struct p2m_domain *)info)->ept;
>>> -
>>> -    __invept(INVEPT_SINGLE_CONTEXT, ept_get_eptp(ept), 0);
>>> +    /*
>>> +     * The invalidate will be done before VMENTER (see
>>
>> invalidate -> invalidation?
> 
> That would be the correct English grammer, yes.

FWIW I think either one is acceptable English grammar.

 -George