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nEPT: Add nEPT violation/misconfigration support
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Inject nEPT fault to L1 guest. This patch is original from Xinhao.

Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Yang Zhang authored and Paolo Bonzini committed Aug 7, 2013
1 parent 5316622 commit 25d9208
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Showing 4 changed files with 95 additions and 14 deletions.
4 changes: 4 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 @@ -286,6 +286,7 @@ struct kvm_mmu {
u64 *pae_root;
u64 *lm_root;
u64 rsvd_bits_mask[2][4];
u64 bad_mt_xwr;

/*
* Bitmap: bit set = last pte in walk
Expand Down Expand Up @@ -512,6 +513,9 @@ struct kvm_vcpu_arch {
* instruction.
*/
bool write_fault_to_shadow_pgtable;

/* set at EPT violation at this point */
unsigned long exit_qualification;
};

struct kvm_lpage_info {
Expand Down
61 changes: 50 additions & 11 deletions arch/x86/kvm/mmu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3519,6 +3519,8 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
int maxphyaddr = cpuid_maxphyaddr(vcpu);
u64 exb_bit_rsvd = 0;

context->bad_mt_xwr = 0;

if (!context->nx)
exb_bit_rsvd = rsvd_bits(63, 63);
switch (context->root_level) {
Expand Down Expand Up @@ -3574,7 +3576,40 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
}
}

static void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
struct kvm_mmu *context, bool execonly)
{
int maxphyaddr = cpuid_maxphyaddr(vcpu);
int pte;

context->rsvd_bits_mask[0][3] =
rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 7);
context->rsvd_bits_mask[0][2] =
rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 6);
context->rsvd_bits_mask[0][1] =
rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 6);
context->rsvd_bits_mask[0][0] = rsvd_bits(maxphyaddr, 51);

/* large page */
context->rsvd_bits_mask[1][3] = context->rsvd_bits_mask[0][3];
context->rsvd_bits_mask[1][2] =
rsvd_bits(maxphyaddr, 51) | rsvd_bits(12, 29);
context->rsvd_bits_mask[1][1] =
rsvd_bits(maxphyaddr, 51) | rsvd_bits(12, 20);
context->rsvd_bits_mask[1][0] = context->rsvd_bits_mask[0][0];

for (pte = 0; pte < 64; pte++) {
int rwx_bits = pte & 7;
int mt = pte >> 3;
if (mt == 0x2 || mt == 0x3 || mt == 0x7 ||
rwx_bits == 0x2 || rwx_bits == 0x6 ||
(rwx_bits == 0x4 && !execonly))
context->bad_mt_xwr |= (1ull << pte);
}
}

static void update_permission_bitmask(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu, bool ept)
{
unsigned bit, byte, pfec;
u8 map;
Expand All @@ -3592,12 +3627,16 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu
w = bit & ACC_WRITE_MASK;
u = bit & ACC_USER_MASK;

/* Not really needed: !nx will cause pte.nx to fault */
x |= !mmu->nx;
/* Allow supervisor writes if !cr0.wp */
w |= !is_write_protection(vcpu) && !uf;
/* Disallow supervisor fetches of user code if cr4.smep */
x &= !(smep && u && !uf);
if (!ept) {
/* Not really needed: !nx will cause pte.nx to fault */
x |= !mmu->nx;
/* Allow supervisor writes if !cr0.wp */
w |= !is_write_protection(vcpu) && !uf;
/* Disallow supervisor fetches of user code if cr4.smep */
x &= !(smep && u && !uf);
} else
/* Not really needed: no U/S accesses on ept */
u = 1;

fault = (ff && !x) || (uf && !u) || (wf && !w);
map |= fault << bit;
Expand Down Expand Up @@ -3632,7 +3671,7 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu,
context->root_level = level;

reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context);
update_permission_bitmask(vcpu, context, false);
update_last_pte_bitmap(vcpu, context);

ASSERT(is_pae(vcpu));
Expand Down Expand Up @@ -3662,7 +3701,7 @@ static int paging32_init_context(struct kvm_vcpu *vcpu,
context->root_level = PT32_ROOT_LEVEL;

reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context);
update_permission_bitmask(vcpu, context, false);
update_last_pte_bitmap(vcpu, context);

context->new_cr3 = paging_new_cr3;
Expand Down Expand Up @@ -3724,7 +3763,7 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
context->gva_to_gpa = paging32_gva_to_gpa;
}

update_permission_bitmask(vcpu, context);
update_permission_bitmask(vcpu, context, false);
update_last_pte_bitmap(vcpu, context);

return 0;
Expand Down Expand Up @@ -3803,7 +3842,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
g_context->gva_to_gpa = paging32_gva_to_gpa_nested;
}

update_permission_bitmask(vcpu, g_context);
update_permission_bitmask(vcpu, g_context, false);
update_last_pte_bitmap(vcpu, g_context);

return 0;
Expand Down
25 changes: 22 additions & 3 deletions arch/x86/kvm/paging_tmpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -129,10 +129,10 @@ static inline void FNAME(protect_clean_gpte)(unsigned *access, unsigned gpte)

static bool FNAME(is_rsvd_bits_set)(struct kvm_mmu *mmu, u64 gpte, int level)
{
int bit7;
int bit7 = (gpte >> 7) & 1, low6 = gpte & 0x3f;

bit7 = (gpte >> 7) & 1;
return (gpte & mmu->rsvd_bits_mask[bit7][level-1]) != 0;
return (gpte & mmu->rsvd_bits_mask[bit7][level-1]) |
((mmu->bad_mt_xwr & (1ull << low6)) != 0);
}

static inline int FNAME(is_present_gpte)(unsigned long pte)
Expand Down Expand Up @@ -386,6 +386,25 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
walker->fault.vector = PF_VECTOR;
walker->fault.error_code_valid = true;
walker->fault.error_code = errcode;

#if PTTYPE == PTTYPE_EPT
/*
* Use PFERR_RSVD_MASK in error_code to to tell if EPT
* misconfiguration requires to be injected. The detection is
* done by is_rsvd_bits_set() above.
*
* We set up the value of exit_qualification to inject:
* [2:0] - Derive from [2:0] of real exit_qualification at EPT violation
* [5:3] - Calculated by the page walk of the guest EPT page tables
* [7:8] - Derived from [7:8] of real exit_qualification
*
* The other bits are set to 0.
*/
if (!(errcode & PFERR_RSVD_MASK)) {
vcpu->arch.exit_qualification &= 0x187;
vcpu->arch.exit_qualification |= ((pt_access & pte) & 0x7) << 3;
}
#endif
walker->fault.address = addr;
walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu;

Expand Down
19 changes: 19 additions & 0 deletions arch/x86/kvm/vmx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5317,9 +5317,13 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)

/* It is a write fault? */
error_code = exit_qualification & (1U << 1);
/* It is a fetch fault? */
error_code |= (exit_qualification & (1U << 2)) << 2;
/* ept page table is present? */
error_code |= (exit_qualification >> 3) & 0x1;

vcpu->arch.exit_qualification = exit_qualification;

return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
}

Expand Down Expand Up @@ -7348,6 +7352,21 @@ static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
entry->ecx |= bit(X86_FEATURE_VMX);
}

static void nested_ept_inject_page_fault(struct kvm_vcpu *vcpu,
struct x86_exception *fault)
{
struct vmcs12 *vmcs12;
nested_vmx_vmexit(vcpu);
vmcs12 = get_vmcs12(vcpu);

if (fault->error_code & PFERR_RSVD_MASK)
vmcs12->vm_exit_reason = EXIT_REASON_EPT_MISCONFIG;
else
vmcs12->vm_exit_reason = EXIT_REASON_EPT_VIOLATION;
vmcs12->exit_qualification = vcpu->arch.exit_qualification;
vmcs12->guest_physical_address = fault->address;
}

/*
* prepare_vmcs02 is called when the L1 guest hypervisor runs its nested
* L2 guest. L1 has a vmcs for L2 (vmcs12), and this function "merges" it
Expand Down

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