Re: [Xen-devel] [PATCH v2 1/2] x86/mem_event: Deliver gla fault EPT violation information

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/08/2014 22:53, Tamas Lengyel wrote:
> On Thu, Aug 7, 2014 at 11:39 PM, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx
>> wrote:
>> On 08/07/2014 03:47 PM, Tamas K Lengyel wrote:
>>
>>> On Intel EPT the exit qualification generated by a violation also
>>> includes a bit (EPT_GLA_FAULT) which describes the following information:
>>> Set if the access causing the EPT violation is to a guest-physical
>>> address that is the translation of a linear address. Clear if the access
>>> causing the EPT violation is to a paging-structure entry as part of a page
>>> walk or the update of an accessed or dirty bit.
>>>
>>> For more information see Table 27-7 in the Intel SDM.
>>>
>>> This patch extends the mem_event system to deliver this extra
>>> information, which could be useful for determining the cause of a violation.
>>>
>>> v2: Split gla_fault into fault_in_gpt and fault_gla to be more compatible
>>> with the AMD implementation.
>>>
>>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
>>> ---
>>>   xen/arch/x86/hvm/hvm.c         |  8 ++++++--
>>>   xen/arch/x86/hvm/svm/svm.c     |  2 +-
>>>   xen/arch/x86/hvm/vmx/vmx.c     | 23 ++++++++++++++++++++++-
>>>   xen/arch/x86/mm/p2m.c          |  5 ++++-
>>>   xen/include/asm-x86/hvm/hvm.h  |  5 ++++-
>>>   xen/include/asm-x86/p2m.h      |  3 ++-
>>>   xen/include/public/mem_event.h |  4 +++-
>>>   7 files changed, 42 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
>>> index e834406..d7b5e2b 100644
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -2725,6 +2725,8 @@ void hvm_inject_page_fault(int errcode, unsigned
>>> long cr2)
>>>   int hvm_hap_nested_page_fault(paddr_t gpa,
>>>                                 bool_t gla_valid,
>>>                                 unsigned long gla,
>>> +                              bool_t fault_in_gpt,
>>> +                              bool_t fault_gla,
>>>                                 bool_t access_r,
>>>                                 bool_t access_w,
>>>                                 bool_t access_x)
>>> @@ -2832,8 +2834,10 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
>>>             if ( violation )
>>>           {
>>> -            if ( p2m_mem_access_check(gpa, gla_valid, gla, access_r,
>>> -                                        access_w, access_x, &req_ptr) )
>>> +            if ( p2m_mem_access_check(gpa, gla_valid, gla,
>>> +                                        fault_in_gpt, fault_gla,
>>> +                                        access_r, access_w, access_x,
>>> +                                        &req_ptr) )
>>>               {
>>>                   fall_through = 1;
>>>               } else {
>>> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
>>> index 76616ac..9e35e7a 100644
>>> --- a/xen/arch/x86/hvm/svm/svm.c
>>> +++ b/xen/arch/x86/hvm/svm/svm.c
>>> @@ -1403,7 +1403,7 @@ static void svm_do_nested_pgfault(struct vcpu *v,
>>>       p2m_access_t p2ma;
>>>       struct p2m_domain *p2m = NULL;
>>>   -    ret = hvm_hap_nested_page_fault(gpa, 0, ~0ul,
>>> +    ret = hvm_hap_nested_page_fault(gpa, 0, ~0ul, 0, 0,
>>>
>>
>> Why not pass the actual bits that the HW provides?
>>
> The actual bits could be passed but it makes no difference at this point
> since the AMD side isn't setup to work with mem_event. When it is
> integrated, those bits could and should be passed accordingly.
>
> Tamas

There is a lot more than mem_event which might want these bits from AMD.

If the bits are easily available at this point, you should fill them in.

~Andrew

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