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KVM, pkeys: introduce pkru_mask to cache conditions 

PKEYS defines a new status bit in the PFEC. PFEC.PK (bit 5), if some
conditions is true, the fault is considered as a PKU violation.
pkru_mask indicates if we need to check PKRU.ADi and PKRU.WDi, and
does cache some conditions for permission_fault.

[ Huaitong: Xiao helps to modify many sections. ]

Signed-off-by: Huaitong Han <huaitong.han@intel.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Huaitong Han 2016-03-22 16:51:19 +08:00 committed by Paolo Bonzini
parent 1be0e61c1f
commit 2d344105f5
2 changed files with 88 additions and 0 deletions
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8
arch/x86/include/asm/kvm_host.h
View File

@ -335,6 +335,14 @@ struct kvm_mmu {
*/
u8 permissions[16];
/*
* The pkru_mask indicates if protection key checks are needed. It
* consists of 16 domains indexed by page fault error code bits [4:1],
* with PFEC.RSVD replaced by ACC_USER_MASK from the page tables.
* Each domain has 2 bits which are ANDed with AD and WD from PKRU.
*/
u32 pkru_mask;
u64 *pae_root;
u64 *lm_root;

80
arch/x86/kvm/mmu.c
View File

@ -3923,6 +3923,81 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu,
}
}
/*
* PKU is an additional mechanism by which the paging controls access to
* user-mode addresses based on the value in the PKRU register. Protection
* key violations are reported through a bit in the page fault error code.
* Unlike other bits of the error code, the PK bit is not known at the
* call site of e.g. gva_to_gpa; it must be computed directly in
* permission_fault based on two bits of PKRU, on some machine state (CR4,
* CR0, EFER, CPL), and on other bits of the error code and the page tables.
*
* In particular the following conditions come from the error code, the
* page tables and the machine state:
* - PK is always zero unless CR4.PKE=1 and EFER.LMA=1
* - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch)
* - PK is always zero if U=0 in the page tables
* - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access.
*
* The PKRU bitmask caches the result of these four conditions. The error
* code (minus the P bit) and the page table's U bit form an index into the
* PKRU bitmask. Two bits of the PKRU bitmask are then extracted and ANDed
* with the two bits of the PKRU register corresponding to the protection key.
* For the first three conditions above the bits will be 00, thus masking
* away both AD and WD. For all reads or if the last condition holds, WD
* only will be masked away.
*/
static void update_pkru_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
bool ept)
{
unsigned bit;
bool wp;
if (ept) {
mmu->pkru_mask = 0;
return;
}
/* PKEY is enabled only if CR4.PKE and EFER.LMA are both set. */
if (!kvm_read_cr4_bits(vcpu, X86_CR4_PKE) || !is_long_mode(vcpu)) {
mmu->pkru_mask = 0;
return;
}
wp = is_write_protection(vcpu);
for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {
unsigned pfec, pkey_bits;
bool check_pkey, check_write, ff, uf, wf, pte_user;
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;
/*
* Only need to check the access which is not an
* instruction fetch and is to a user page.
*/
check_pkey = (!ff && pte_user);
/*
* write access is controlled by PKRU if it is a
* user access or CR0.WP = 1.
*/
check_write = check_pkey && wf && (uf || wp);
/* PKRU.AD stops both read and write access. */
pkey_bits = !!check_pkey;
/* PKRU.WD stops write access. */
pkey_bits |= (!!check_write) << 1;
mmu->pkru_mask |= (pkey_bits & 3) << pfec;
}
}
static void update_last_nonleaf_level(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
unsigned root_level = mmu->root_level;
@ -3941,6 +4016,7 @@ static void paging64_init_context_common(struct kvm_vcpu *vcpu,
reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context, false);
update_pkru_bitmask(vcpu, context, false);
update_last_nonleaf_level(vcpu, context);
MMU_WARN_ON(!is_pae(vcpu));
@ -3968,6 +4044,7 @@ static void paging32_init_context(struct kvm_vcpu *vcpu,
reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context, false);
update_pkru_bitmask(vcpu, context, false);
update_last_nonleaf_level(vcpu, context);
context->page_fault = paging32_page_fault;
@ -4026,6 +4103,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
}
update_permission_bitmask(vcpu, context, false);
update_pkru_bitmask(vcpu, context, false);
update_last_nonleaf_level(vcpu, context);
reset_tdp_shadow_zero_bits_mask(vcpu, context);
}
@ -4078,6 +4156,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly)
context->direct_map = false;
update_permission_bitmask(vcpu, context, true);
update_pkru_bitmask(vcpu, context, true);
reset_rsvds_bits_mask_ept(vcpu, context, execonly);
reset_ept_shadow_zero_bits_mask(vcpu, context, execonly);
}
@ -4132,6 +4211,7 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
}
update_permission_bitmask(vcpu, g_context, false);
update_pkru_bitmask(vcpu, g_context, false);
update_last_nonleaf_level(vcpu, g_context);
}