Re: [Xen-devel] [PATCH 01/10] VMX: Enable EPT A/D bit support

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/03/15 14:35, Kai Huang wrote:
> On Mon, Mar 30, 2015 at 5:36 PM, Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 30/03/15 07:11, Kai Huang wrote:
>>>
>>> On 03/28/2015 04:38 AM, Andrew Cooper wrote:
>>>> On 27/03/15 02:35, Kai Huang wrote:
>>>>> PML requires A/D bit support so enable it for further use.
>>>>>
>>>>> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
>>>>> ---
>>>>>   xen/arch/x86/hvm/vmx/vmcs.c        | 1 +
>>>>>   xen/arch/x86/mm/p2m-ept.c          | 8 +++++++-
>>>>>   xen/include/asm-x86/hvm/vmx/vmcs.h | 4 +++-
>>>>>   xen/include/asm-x86/hvm/vmx/vmx.h  | 5 ++++-
>>>>>   4 files changed, 15 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
>>>>> index d614638..2f645fe 100644
>>>>> --- a/xen/arch/x86/hvm/vmx/vmcs.c
>>>>> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
>>>>> @@ -103,6 +103,7 @@ static void __init vmx_display_features(void)
>>>>>       P(cpu_has_vmx_tpr_shadow, "APIC TPR shadow");
>>>>>       P(cpu_has_vmx_ept, "Extended Page Tables (EPT)");
>>>>>       P(cpu_has_vmx_vpid, "Virtual-Processor Identifiers (VPID)");
>>>>> +    P(cpu_has_vmx_ept_ad_bit, "EPT A/D bit");
>>>>>       P(cpu_has_vmx_vnmi, "Virtual NMI");
>>>>>       P(cpu_has_vmx_msr_bitmap, "MSR direct-access bitmap");
>>>>>       P(cpu_has_vmx_unrestricted_guest, "Unrestricted Guest");
>>>>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
>>>>> index c2d7720..8650092 100644
>>>>> --- a/xen/arch/x86/mm/p2m-ept.c
>>>>> +++ b/xen/arch/x86/mm/p2m-ept.c
>>>>> @@ -233,6 +233,9 @@ static int ept_split_super_page(struct
>>>>> p2m_domain *p2m, ept_entry_t *ept_entry,
>>>>>       if ( !ept_set_middle_entry(p2m, &neThanks,
> -Kaiw_ept) )
>>>>>           return 0;
>>>>>   +    /* It's better to copy A bit of Middle entry from original
>>>>> entry */
>>>>> +    new_ept.a = ept_entry->a;
>>>> Surely d needs to be propagated as well?
>>> No it's not necessary. D-bit is not defined in middle level EPT table.
>>> Only leaf table entry has D-bit definition.
>> Ok - so the middle doesn't have a D.
>>
>> What about the superpage having D set? Surely that needs propagated down
>> to the new shattered leaves?
> Yes shattered leaves will inherit both A and D bits from the original
> superpage entry in " *epte = *ept_entry; " statement in below code in
> ept_split_super_page.
>
>     for ( int i = 0; i < EPT_PAGETABLE_ENTRIES; i++ )
>     {
>         ept_entry_t *epte = table + i;
>
>         *epte = *ept_entry;
>         ......

So you are.  Apologies for the confusion.

~Andrew


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