[RFC v2 4/7] KVM: MMU: Refactor pkr_mask to cache condition

[Chenyi Qiang]

pkr_mask bitmap indicates if protection key checks are needed for user
pages currently. It is indexed by page fault error code bits [4:1] with
PFEC.RSVD replaced by the ACC_USER_MASK from the page tables. Refactor
it by reverting to the use of PFEC.RSVD. After that, PKS and PKU can
share the same bitmap.

Signed-off-by: Chenyi Qiang <chenyi.qi...@intel.com>
---
 arch/x86/kvm/mmu.h     | 10 ++++++----
 arch/x86/kvm/mmu/mmu.c | 16 ++++++++++------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 306608248594..597b9159c10b 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -204,11 +204,13 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, 
struct kvm_mmu *mmu,
                * index of the protection domain, so pte_pkey * 2 is
                * is the index of the first bit for the domain.
                */
-               pkr_bits = (vcpu->arch.pkru >> (pte_pkey * 2)) & 3;
+               if (pte_access & PT_USER_MASK)
+                       pkr_bits = (vcpu->arch.pkru >> (pte_pkey * 2)) & 3;
+               else
+                       pkr_bits = 0;
 
-               /* clear present bit, replace PFEC.RSVD with ACC_USER_MASK. */
-               offset = (pfec & ~1) +
-                       ((pte_access & PT_USER_MASK) << (PFERR_RSVD_BIT - 
PT_USER_SHIFT));
+               /* clear present bit */
+               offset = (pfec & ~1);
 
                pkr_bits &= mmu->pkr_mask >> offset;
                errcode |= -pkr_bits & PFERR_PK_MASK;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 834a95cf49fa..f9814ab0596d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4716,21 +4716,25 @@ static void update_pkr_bitmask(struct kvm_vcpu *vcpu, 
struct kvm_mmu *mmu,
 
        for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {
                unsigned pfec, pkey_bits;
-               bool check_pkey, check_write, ff, uf, wf, pte_user;
+               bool check_pkey, check_write, ff, uf, wf, rsvdf;
 
                pfec = bit << 1;
                ff = pfec & PFERR_FETCH_MASK;
                uf = pfec & PFERR_USER_MASK;
                wf = pfec & PFERR_WRITE_MASK;
 
-               /* PFEC.RSVD is replaced by ACC_USER_MASK. */
-               pte_user = pfec & PFERR_RSVD_MASK;
+               /*
+                * PFERR_RSVD_MASK bit is not set if the
+                * access is subject to PK restrictions.
+                */
+               rsvdf = pfec & PFERR_RSVD_MASK;
 
                /*
-                * Only need to check the access which is not an
-                * instruction fetch and is to a user page.
+                * need to check the access which is not an
+                * instruction fetch and is not a rsvd fault.
                 */
-               check_pkey = (!ff && pte_user);
+               check_pkey = (!ff && !rsvdf);
+
                /*
                 * write access is controlled by PKRU if it is a
                 * user access or CR0.WP = 1.
-- 
2.17.1