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KVM: MMU: Emulate #PF error code of reserved bits violation
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Detect, indicate, and propagate page faults where reserved bits are set.
Take care to handle the different paging modes, each of which has different
sets of reserved bits.

[avi: fix pte reserved bits for efer.nxe=0]

Signed-off-by: Eddie Dong <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
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@dongyaozu @avikivity
dongyaozu authored and avikivity committed Jun 10, 2009
1 parent 362c105 commit 82725b2
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Showing 4 changed files with 88 additions and 0 deletions.
2 changes: 2 additions & 0 deletions arch/x86/include/asm/kvm_host.h
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Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,7 @@ struct kvm_mmu {
union kvm_mmu_page_role base_role;

u64 *pae_root;
u64 rsvd_bits_mask[2][4];
};

struct kvm_vcpu_arch {
Expand Down Expand Up @@ -791,5 +792,6 @@ asmlinkage void kvm_handle_fault_on_reboot(void);
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
int kvm_age_hva(struct kvm *kvm, unsigned long hva);
int cpuid_maxphyaddr(struct kvm_vcpu *vcpu);

#endif /* _ASM_X86_KVM_HOST_H */
69 changes: 69 additions & 0 deletions arch/x86/kvm/mmu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,7 @@ module_param(oos_shadow, bool, 0644);
#define PFERR_PRESENT_MASK (1U << 0)
#define PFERR_WRITE_MASK (1U << 1)
#define PFERR_USER_MASK (1U << 2)
#define PFERR_RSVD_MASK (1U << 3)
#define PFERR_FETCH_MASK (1U << 4)

#define PT_DIRECTORY_LEVEL 2
Expand Down Expand Up @@ -179,6 +180,11 @@ static u64 __read_mostly shadow_accessed_mask;
static u64 __read_mostly shadow_dirty_mask;
static u64 __read_mostly shadow_mt_mask;

static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
}

void kvm_mmu_set_nonpresent_ptes(u64 trap_pte, u64 notrap_pte)
{
shadow_trap_nonpresent_pte = trap_pte;
Expand Down Expand Up @@ -2151,6 +2157,14 @@ static void paging_free(struct kvm_vcpu *vcpu)
nonpaging_free(vcpu);
}

static bool is_rsvd_bits_set(struct kvm_vcpu *vcpu, u64 gpte, int level)
{
int bit7;

bit7 = (gpte >> 7) & 1;
return (gpte & vcpu->arch.mmu.rsvd_bits_mask[bit7][level-1]) != 0;
}

#define PTTYPE 64
#include "paging_tmpl.h"
#undef PTTYPE
Expand All @@ -2159,6 +2173,55 @@ static void paging_free(struct kvm_vcpu *vcpu)
#include "paging_tmpl.h"
#undef PTTYPE

static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, int level)
{
struct kvm_mmu *context = &vcpu->arch.mmu;
int maxphyaddr = cpuid_maxphyaddr(vcpu);
u64 exb_bit_rsvd = 0;

if (!is_nx(vcpu))
exb_bit_rsvd = rsvd_bits(63, 63);
switch (level) {
case PT32_ROOT_LEVEL:
/* no rsvd bits for 2 level 4K page table entries */
context->rsvd_bits_mask[0][1] = 0;
context->rsvd_bits_mask[0][0] = 0;
if (is_cpuid_PSE36())
/* 36bits PSE 4MB page */
context->rsvd_bits_mask[1][1] = rsvd_bits(17, 21);
else
/* 32 bits PSE 4MB page */
context->rsvd_bits_mask[1][1] = rsvd_bits(13, 21);
context->rsvd_bits_mask[1][0] = ~0ull;
break;
case PT32E_ROOT_LEVEL:
context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 62); /* PDE */
context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 62); /* PTE */
context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 62) |
rsvd_bits(13, 20); /* large page */
context->rsvd_bits_mask[1][0] = ~0ull;
break;
case PT64_ROOT_LEVEL:
context->rsvd_bits_mask[0][3] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
context->rsvd_bits_mask[0][2] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 51);
context->rsvd_bits_mask[1][3] = context->rsvd_bits_mask[0][3];
context->rsvd_bits_mask[1][2] = context->rsvd_bits_mask[0][2];
context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
rsvd_bits(maxphyaddr, 51) | rsvd_bits(13, 20);
context->rsvd_bits_mask[1][0] = ~0ull;
break;
}
}

static int paging64_init_context_common(struct kvm_vcpu *vcpu, int level)
{
struct kvm_mmu *context = &vcpu->arch.mmu;
Expand All @@ -2179,13 +2242,15 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu, int level)

static int paging64_init_context(struct kvm_vcpu *vcpu)
{
reset_rsvds_bits_mask(vcpu, PT64_ROOT_LEVEL);
return paging64_init_context_common(vcpu, PT64_ROOT_LEVEL);
}

static int paging32_init_context(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *context = &vcpu->arch.mmu;

reset_rsvds_bits_mask(vcpu, PT32_ROOT_LEVEL);
context->new_cr3 = paging_new_cr3;
context->page_fault = paging32_page_fault;
context->gva_to_gpa = paging32_gva_to_gpa;
Expand All @@ -2201,6 +2266,7 @@ static int paging32_init_context(struct kvm_vcpu *vcpu)

static int paging32E_init_context(struct kvm_vcpu *vcpu)
{
reset_rsvds_bits_mask(vcpu, PT32E_ROOT_LEVEL);
return paging64_init_context_common(vcpu, PT32E_ROOT_LEVEL);
}

Expand All @@ -2221,12 +2287,15 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
context->gva_to_gpa = nonpaging_gva_to_gpa;
context->root_level = 0;
} else if (is_long_mode(vcpu)) {
reset_rsvds_bits_mask(vcpu, PT64_ROOT_LEVEL);
context->gva_to_gpa = paging64_gva_to_gpa;
context->root_level = PT64_ROOT_LEVEL;
} else if (is_pae(vcpu)) {
reset_rsvds_bits_mask(vcpu, PT32E_ROOT_LEVEL);
context->gva_to_gpa = paging64_gva_to_gpa;
context->root_level = PT32E_ROOT_LEVEL;
} else {
reset_rsvds_bits_mask(vcpu, PT32_ROOT_LEVEL);
context->gva_to_gpa = paging32_gva_to_gpa;
context->root_level = PT32_ROOT_LEVEL;
}
Expand Down
7 changes: 7 additions & 0 deletions arch/x86/kvm/paging_tmpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
gfn_t table_gfn;
unsigned index, pt_access, pte_access;
gpa_t pte_gpa;
int rsvd_fault = 0;

pgprintk("%s: addr %lx\n", __func__, addr);
walk:
Expand Down Expand Up @@ -157,6 +158,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
if (!is_present_pte(pte))
goto not_present;

rsvd_fault = is_rsvd_bits_set(vcpu, pte, walker->level);
if (rsvd_fault)
goto access_error;

if (write_fault && !is_writeble_pte(pte))
if (user_fault || is_write_protection(vcpu))
goto access_error;
Expand Down Expand Up @@ -232,6 +237,8 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
walker->error_code |= PFERR_USER_MASK;
if (fetch_fault)
walker->error_code |= PFERR_FETCH_MASK;
if (rsvd_fault)
walker->error_code |= PFERR_RSVD_MASK;
return 0;
}

Expand Down
10 changes: 10 additions & 0 deletions arch/x86/kvm/x86.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3017,6 +3017,16 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
return best;
}

int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;

best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
if (best)
return best->eax & 0xff;
return 36;
}

void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
u32 function, index;
Expand Down

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