On 03/05/2016 07:27 PM, Huaitong Han wrote:
Protection keys define a new 4-bit protection key field (PKEY) in bits
62:59 of leaf entries of the page tables, the PKEY is an index to PKRU
register(16 domains), every domain has 2 bits(write disable bit, access
disable bit).
Static logic has been produced in update_permission_bitmask, dynamic logic
need read pkey from page table entries, get pkru value, and deduce the
correct result.
Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>
---
Changes in v4:
*Patch has rebased on http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/log/?h=mm/pkeys
pte_pkey function has been deleted in kernel PKU support, so KVM patches use
pte_flags_pkey(pte_flags(pte)) instead of pte_pkey(pte).
arch/x86/kvm/mmu.h | 56 +++++++++++++++++++++++++++++++++++++++++-----
arch/x86/kvm/paging_tmpl.h | 18 ++++++++++++---
arch/x86/kvm/x86.c | 2 +-
3 files changed, 67 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 55ffb7b..7a9f627 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -3,6 +3,7 @@
#include <linux/kvm_host.h>
#include "kvm_cache_regs.h"
+#include "x86.h"
#define PT64_PT_BITS 9
#define PT64_ENT_PER_PAGE (1 << PT64_PT_BITS)
@@ -24,6 +25,7 @@
#define PT_PAGE_SIZE_MASK (1ULL << PT_PAGE_SIZE_SHIFT)
#define PT_PAT_MASK (1ULL << 7)
#define PT_GLOBAL_MASK (1ULL << 8)
+
#define PT64_NX_SHIFT 63
#define PT64_NX_MASK (1ULL << PT64_NX_SHIFT)
@@ -45,6 +47,10 @@
#define PT_PAGE_TABLE_LEVEL 1
#define PT_MAX_HUGEPAGE_LEVEL (PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES - 1)
+#define PKRU_READ 0
+#define PKRU_WRITE 1
+#define PKRU_ATTRS 2
+
static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
@@ -145,10 +151,50 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu)
* fault with the given access (in ACC_* format)?
*/
static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
- unsigned pte_access, unsigned pfec)
+ unsigned pte_access, unsigned pte_pkeys, unsigned pfec)
{
- int cpl = kvm_x86_ops->get_cpl(vcpu);
- unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
+ unsigned long smap, rflags;
+ u32 pkru, pkru_bits;
+ int cpl, index;
+ bool wf, uf;
+
+ cpl = kvm_x86_ops->get_cpl(vcpu);
+ rflags = kvm_x86_ops->get_rflags(vcpu);
+
+ /*
+ * PKU is computed dynamically in permission_fault.
+ * 2nd and 6th conditions:
+ * 2.EFER_LMA=1
+ * 6.PKRU.AD=1
+ * or The access is a data write and PKRU.WD=1 and
+ * either CR0.WP=1 or it is a user mode access
+ */
+ pkru = is_long_mode(vcpu) ? read_pkru() : 0;
+ if (unlikely(pkru) && (pfec & PFERR_PK_MASK))
+ {
+ /*
+ * PKRU defines 32 bits, there are 16 domains and 2 attribute bits per
+ * domain in pkru, pkey is the index to a defined domain, so the value
+ * of pkey * PKRU_ATTRS is offset of a defined domain.
+ */
+ pkru_bits = (pkru >> (pte_pkeys * PKRU_ATTRS)) & 3;
+
+ wf = pfec & PFERR_WRITE_MASK;
+ uf = pfec & PFERR_USER_MASK;
+
+ /*
+ * Ignore PKRU.WD if not relevant to this access (a read,
+ * or a supervisor mode access if CR0.WP=0).
+ * So 6th conditions is equivalent to "pkru_bits != 0"
+ */
+ if (!wf || (!uf && !is_write_protection(vcpu)))
+ pkru_bits &= ~(1 << PKRU_WRITE);
+
+ /* Flip pfec on PK bit if pkru_bits is zero */
+ pfec ^= pkru_bits ? 0 : PFERR_PK_MASK;
+ }
+ else
+ pfec &= ~PFERR_PK_MASK;
/*
* If CPL < 3, SMAP prevention are disabled if EFLAGS.AC = 1.
@@ -163,8 +209,8 @@ static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
* but it will be one in index if SMAP checks are being overridden.
* It is important to keep this branchless.
*/
- unsigned long smap = (cpl - 3) & (rflags & X86_EFLAGS_AC);
- int index = (pfec >> 1) +
+ smap = (cpl - 3) & (rflags & X86_EFLAGS_AC);
+ index = (pfec >> 1) +
(smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1));
See my comments in the previous patch.
WARN_ON(pfec & PFERR_RSVD_MASK);
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 6c9fed9..9afc066 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -253,6 +253,15 @@ static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
}
return 0;
}
+static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte)
+{
+ unsigned pkeys = 0;
+#if PTTYPE == 64
+ pte_t pte = {.pte = gpte};
+ pkeys = pte_flags_pkey(pte_flags(pte));
+#endif
It works for PAE guest either.
It is not a problem as the bits used by PKEY are reserved on PAE mode which should
be figured out by is_rsvd_bits_set() prior to this call and PKEY is ignored if
EFER.LMA = 0. But please add some comments here to explain why it is safe.
+ return pkeys;
+}
/*
* Fetch a guest pte for a guest virtual address
@@ -265,12 +274,13 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
pt_element_t pte;
pt_element_t __user *uninitialized_var(ptep_user);
gfn_t table_gfn;
- unsigned index, pt_access, pte_access, accessed_dirty;
+ unsigned index, pt_access, pte_access, accessed_dirty, pte_pkeys;
gpa_t pte_gpa;
int offset;
const int write_fault = access & PFERR_WRITE_MASK;
const int user_fault = access & PFERR_USER_MASK;
const int fetch_fault = access & PFERR_FETCH_MASK;
+ const int pk_fault = access & PFERR_PK_MASK;
u16 errcode = 0;
gpa_t real_gpa;
gfn_t gfn;
@@ -356,7 +366,9 @@ retry_walk:
walker->ptes[walker->level - 1] = pte;
} while (!is_last_gpte(mmu, walker->level, pte));
- if (unlikely(permission_fault(vcpu, mmu, pte_access, access))) {
+ pte_pkeys = FNAME(gpte_pkeys)(vcpu, pte);
+ if (unlikely(permission_fault(vcpu, mmu, pte_access, pte_pkeys,
+ access))) {
errcode |= PFERR_PRESENT_MASK;
goto error;
}
@@ -399,7 +411,7 @@ retry_walk:
return 1;
error:
- errcode |= write_fault | user_fault;
+ errcode |= write_fault | user_fault | pk_fault;
No. The pk_fault is not always caused by guest page table as it's depends on
CR0.WP which is always true on shadow page table.
if (fetch_fault && (mmu->nx ||
kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)))
errcode |= PFERR_FETCH_MASK;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 05e7838..b697a99 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4317,7 +4317,7 @@ static int vcpu_mmio_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva,
if (vcpu_match_mmio_gva(vcpu, gva)
&& !permission_fault(vcpu, vcpu->arch.walk_mmu,
- vcpu->arch.access, access)) {
+ vcpu->arch.access, 0, access)) {
No. The pkey is not always 0.
We should cache PKEY for the mmio access and use it here to check if the right
is adequate.
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