On 03/25/2016 10:21 PM, Paolo Bonzini wrote:
On 25/03/2016 14:19, Xiao Guangrong wrote:
WARN_ON(pfec & (PFERR_PK_MASK | PFERR_RSVD_MASK));
- pfec |= PFERR_PRESENT_MASK;
+ errcode = PFERR_PRESENT_MASK;
if (unlikely(mmu->pkru_mask)) {
u32 pkru_bits, offset;
@@ -193,11 +193,11 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
((pte_access & PT_USER_MASK) << (PFERR_RSVD_BIT - PT_USER_SHIFT));
pkru_bits &= mmu->pkru_mask >> offset;
- pfec |= -pkru_bits & PFERR_PK_MASK;
+ errcode |= -pkru_bits & PFERR_PK_MASK;
fault |= (pkru_bits != 0);
}
- return -(uint32_t)fault & pfec;
+ return -(uint32_t)fault & errcode;
}
I have another doubt here.
If you get a fault due to U=0, you would not get PFERR_PK_MASK. This
is checked implicitly through the pte_user bit which we moved to
PFERR_RSVD_BIT. However, if you get a fault due to W=0 _and_
PKRU.AD=1 or PKRU.WD=1 for the page's protection key, would the PK
bit be set in the error code? If not, we would need something like
this:
Based on the SDM:
PK flag (bit 5).
This flag is 1 if (1) IA32_EFER.LMA = CR4.PKE = 1; (2) the access causing the page-fault exception
was a data access; (3) the linear address was a user-mode address with protection key i; and (5) the
PKRU register (see Section 4.6.2) is such that either (a) ADi = 1; or (b) the following all hold:
(i) WDi = 1; (ii) the access is a write access; and (iii) either CR0.WP = 1 or the access causing
the page-fault exception was a user-mode access.
So I think PKEY check and ordinary check are independent, i.e, PFEC.PKEY may be
set even if the on permission on the page table is not adequate.
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