Re: [PATCH v3] KVM: vmx: fix ept reserved bits for 1-GByte page

Wanpeng Li
2014-08-20T07:30:38Z

On Wed, Aug 20, 2014 at 08:51:38AM +0200, Paolo Bonzini wrote:
>Il 20/08/2014 05:17, Wanpeng Li ha scritto:
>> + else if (spte & (1ULL << 7))
>
>You have to check level == 1 specifically here, or add...
>
>> + /*
>> + * 1GB/2MB page, bits 29:12 or 20:12 reserved respectively,
>> + * level == 1 if the hypervisor is using the ignored bit 7.
>> + */
>> + mask |= (PAGE_SIZE << ((level - 1) * 9)) - PAGE_SIZE;
>> + else
>
>... "if (level > 1)" here.
>
>Otherwise, you're marking bits 6:3 as reserved for 4K pages. This
>should cause a WARN, because KVM puts 0110 in those bits:
>
> ret = (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT)
> | VMX_EPT_IPAT_BIT;
>
>(in vmx_get_mt_mask: writeback memory, ignore PAT memory type from the
>guest's page tables)
>

Got it.

Regards,
Wanpeng Li

>How are you testing this patch?
>
>Paolo
>
>> + /* bits 6:3 reserved */
>> + mask |= 0x78;