On 09/11/2015 13:43, Paolo Bonzini wrote:
>
>
> On 09/11/2015 12:54, 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 <[email protected]>
>>
>> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
>> index e4202e4..bbb5555 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 +25,11 @@
>> #define PT_PAGE_SIZE_MASK (1ULL << PT_PAGE_SIZE_SHIFT)
>> #define PT_PAT_MASK (1ULL << 7)
>> #define PT_GLOBAL_MASK (1ULL << 8)
>> +
>> +#define PT64_PKEY_BIT0 (1ULL << _PAGE_BIT_PKEY_BIT0)
>> +#define PT64_PKEY_BIT1 (1ULL << _PAGE_BIT_PKEY_BIT1)
>> +#define PT64_PKEY_BIT2 (1ULL << _PAGE_BIT_PKEY_BIT2)
>> +#define PT64_PKEY_BIT3 (1ULL << _PAGE_BIT_PKEY_BIT3)
>> #define PT64_NX_SHIFT 63
>> #define PT64_NX_MASK (1ULL << PT64_NX_SHIFT)
>>
>> @@ -45,6 +51,15 @@
>> #define PT_PAGE_TABLE_LEVEL 1
>> #define PT_MAX_HUGEPAGE_LEVEL (PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES - 1)
>>
>> +#define PKEYS_BIT0_VALUE (1ULL << 0)
>> +#define PKEYS_BIT1_VALUE (1ULL << 1)
>> +#define PKEYS_BIT2_VALUE (1ULL << 2)
>> +#define PKEYS_BIT3_VALUE (1ULL << 3)
>> +
>> +#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 +160,44 @@ 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;
>> + int cpl, index;
>> + bool wf, uf, pk, pkru_ad, pkru_wd;
>> +
>> + cpl = kvm_x86_ops->get_cpl(vcpu);
>> + rflags = kvm_x86_ops->get_rflags(vcpu);
>> +
>> + pkru = read_pkru();
>> +
>> + /*
>> + * PKRU defines 32 bits, there are 16 domains and 2 attribute bits per
>> + * domain in pkru, pkey is index to a defined domain, so the value of
>> + * pkey * PKRU_ATTRS + R/W is offset of a defined domain attribute.
>> + */
>> + pkru_ad = (pkru >> (pte_pkeys * PKRU_ATTRS + PKRU_READ)) & 1;
>> + pkru_wd = (pkru >> (pte_pkeys * PKRU_ATTRS + PKRU_WRITE)) & 1;
>> +
>> + wf = pfec & PFERR_WRITE_MASK;
>> + uf = pfec & PFERR_USER_MASK;
>> +
>> + /*
>> + * PKeys 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
>> + */
>> + pk = is_long_mode(vcpu) && (pkru_ad ||
>> + (pkru_wd && wf && (is_write_protection(vcpu) || uf)));
A little more optimized:
pkru_bits = (pkru >> (pte_pkeys * PKRU_ATTRS)) & 3;
/*
* Ignore PKRU.WD if not relevant to this access (a read,
* or a supervisor mode access if CR0.WP=0).
*/
if (!wf || (!uf && !is_write_protection(vcpu)))
pkru_bits &= ~(1 << PKRU_WRITE);
... and then just check pkru_bits != 0.
>> + /*
>> + * PK bit right value in pfec equal to
>> + * PK bit current value in pfec and pk value.
>> + */
>> + pfec &= (pk << PFERR_PK_BIT) + ~PFERR_PK_MASK;
>
> PK is only applicable to guest page tables, but if you do not support
> PKRU without EPT (patch 9), none of this is necessary, is it?
Doh. :( Sorry, this is of course needed for the emulation case.
I think you should optimize this for the common case where pkru is zero,
hence pk will always be zero. So something like
pkru = is_long_mode(vcpu) ? read_pkru() : 0;
if (unlikely(pkru) && (pfec & PFERR_PK_MASK)) {
... from above ... */
/* Flip PFERR_PK_MASK if pkru_bits is non-zero */
pfec ^= -pkru_bits & PFERR_PK_MASK;
}
Paolo
>> /*
>> * If CPL < 3, SMAP prevention are disabled if EFLAGS.AC = 1.
>> @@ -163,8 +212,8 @@ 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));
>>
>> WARN_ON(pfec & PFERR_RSVD_MASK);
>> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
>> index 736e6ab..99563bc 100644
>> --- a/arch/x86/kvm/paging_tmpl.h
>> +++ b/arch/x86/kvm/paging_tmpl.h
>> @@ -253,6 +253,17 @@ 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
>> + pkeys = ((gpte & PT64_PKEY_BIT0) ? PKEYS_BIT0_VALUE : 0) |
>> + ((gpte & PT64_PKEY_BIT1) ? PKEYS_BIT1_VALUE : 0) |
>> + ((gpte & PT64_PKEY_BIT2) ? PKEYS_BIT2_VALUE : 0) |
>> + ((gpte & PT64_PKEY_BIT3) ? PKEYS_BIT3_VALUE : 0);
>
> This is just pkeys = (gpte >> _PAGE_BIT_PKEY_BIT0) & 15.
>
> Paolo
>
>> +#endif
>> + return pkeys;
>> +}
>>
>> /*
>> * Fetch a guest pte for a guest virtual address
>> @@ -265,12 +276,13 @@ 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 +368,9 @@ 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 +413,7 @@ retry_walk:
>> return 1;
>>
>> error:
>> - errcode |= write_fault | user_fault;
>> + errcode |= write_fault | user_fault | pk_fault;
>> 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 5181834..7a84b83 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -4107,7 +4107,7 @@ 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)) {
>> *gpa = vcpu->arch.mmio_gfn << PAGE_SHIFT |
>> (gva & (PAGE_SIZE - 1));
>> trace_vcpu_match_mmio(gva, *gpa, write, false);
>>
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