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KVM: x86/mmu: split cpu_role from mmu_role
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Snapshot the state of the processor registers that govern page walk into
a new field of struct kvm_mmu.  This is a more natural representation
than having it *mostly* in mmu_role but not exclusively; the delta
right now is represented in other fields, such as root_level.

The nested MMU now has only the CPU role; and in fact the new function
kvm_calc_cpu_role is analogous to the previous kvm_calc_nested_mmu_role,
except that it has role.base.direct equal to !CR0.PG.  For a walk-only
MMU, "direct" has no meaning, but we set it to !CR0.PG so that
role.ext.cr0_pg can go away in a future patch.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Paolo Bonzini committed Apr 29, 2022
1 parent b898050 commit e5ed0fb
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Showing 3 changed files with 70 additions and 42 deletions.
1 change: 1 addition & 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 @@ -438,6 +438,7 @@ struct kvm_mmu {
struct kvm_mmu_page *sp);
void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
struct kvm_mmu_root_info root;
union kvm_mmu_role cpu_role;
union kvm_mmu_role mmu_role;
u8 root_level;
u8 shadow_root_level;
Expand Down
109 changes: 68 additions & 41 deletions arch/x86/kvm/mmu/mmu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -222,7 +222,7 @@ BUILD_MMU_ROLE_REGS_ACCESSOR(efer, lma, EFER_LMA);
#define BUILD_MMU_ROLE_ACCESSOR(base_or_ext, reg, name) \
static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu) \
{ \
return !!(mmu->mmu_role. base_or_ext . reg##_##name); \
return !!(mmu->cpu_role. base_or_ext . reg##_##name); \
}
BUILD_MMU_ROLE_ACCESSOR(ext, cr0, pg);
BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
Expand Down Expand Up @@ -4748,6 +4748,41 @@ static void paging32_init_context(struct kvm_mmu *context)
context->direct_map = false;
}

static union kvm_mmu_role
kvm_calc_cpu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
{
union kvm_mmu_role role = {0};

role.base.access = ACC_ALL;
role.base.smm = is_smm(vcpu);
role.base.guest_mode = is_guest_mode(vcpu);
role.ext.valid = 1;

if (!____is_cr0_pg(regs)) {
role.base.direct = 1;
return role;
}

role.base.efer_nx = ____is_efer_nx(regs);
role.base.cr0_wp = ____is_cr0_wp(regs);
role.base.smep_andnot_wp = ____is_cr4_smep(regs) && !____is_cr0_wp(regs);
role.base.smap_andnot_wp = ____is_cr4_smap(regs) && !____is_cr0_wp(regs);
role.base.has_4_byte_gpte = !____is_cr4_pae(regs);
role.base.level = role_regs_to_root_level(regs);

role.ext.cr0_pg = 1;
role.ext.cr4_pae = ____is_cr4_pae(regs);
role.ext.cr4_smep = ____is_cr4_smep(regs);
role.ext.cr4_smap = ____is_cr4_smap(regs);
role.ext.cr4_pse = ____is_cr4_pse(regs);

/* PKEY and LA57 are active iff long mode is active. */
role.ext.cr4_pke = ____is_efer_lma(regs) && ____is_cr4_pke(regs);
role.ext.cr4_la57 = ____is_efer_lma(regs) && ____is_cr4_la57(regs);
role.ext.efer_lma = ____is_efer_lma(regs);
return role;
}

static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
Expand Down Expand Up @@ -4807,13 +4842,16 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
struct kvm_mmu *context = &vcpu->arch.root_mmu;
union kvm_mmu_role new_role =
union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, regs);
union kvm_mmu_role mmu_role =
kvm_calc_tdp_mmu_root_page_role(vcpu, regs);

if (new_role.as_u64 == context->mmu_role.as_u64)
if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
mmu_role.as_u64 == context->mmu_role.as_u64)
return;

context->mmu_role.as_u64 = new_role.as_u64;
context->cpu_role.as_u64 = cpu_role.as_u64;
context->mmu_role.as_u64 = mmu_role.as_u64;
context->page_fault = kvm_tdp_page_fault;
context->sync_page = nonpaging_sync_page;
context->invlpg = NULL;
Expand Down Expand Up @@ -4868,24 +4906,26 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu,
}

static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
const struct kvm_mmu_role_regs *regs,
union kvm_mmu_role new_role)
union kvm_mmu_role cpu_role,
union kvm_mmu_role mmu_role)
{
if (new_role.as_u64 == context->mmu_role.as_u64)
if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
mmu_role.as_u64 == context->mmu_role.as_u64)
return;

context->mmu_role.as_u64 = new_role.as_u64;
context->cpu_role.as_u64 = cpu_role.as_u64;
context->mmu_role.as_u64 = mmu_role.as_u64;

if (!is_cr0_pg(context))
nonpaging_init_context(context);
else if (is_cr4_pae(context))
paging64_init_context(context);
else
paging32_init_context(context);
context->root_level = role_regs_to_root_level(regs);
context->root_level = cpu_role.base.level;

reset_guest_paging_metadata(vcpu, context);
context->shadow_root_level = new_role.base.level;
context->shadow_root_level = mmu_role.base.level;

reset_shadow_zero_bits_mask(vcpu, context);
}
Expand All @@ -4894,10 +4934,11 @@ static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
struct kvm_mmu *context = &vcpu->arch.root_mmu;
union kvm_mmu_role new_role =
union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, regs);
union kvm_mmu_role mmu_role =
kvm_calc_shadow_mmu_root_page_role(vcpu, regs);

shadow_mmu_init_context(vcpu, context, regs, new_role);
shadow_mmu_init_context(vcpu, context, cpu_role, mmu_role);
}

static union kvm_mmu_role
Expand All @@ -4922,11 +4963,10 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
.cr4 = cr4 & ~X86_CR4_PKE,
.efer = efer,
};
union kvm_mmu_role new_role;

new_role = kvm_calc_shadow_npt_root_page_role(vcpu, &regs);
union kvm_mmu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);
union kvm_mmu_role mmu_role = kvm_calc_shadow_npt_root_page_role(vcpu, &regs);

shadow_mmu_init_context(vcpu, context, &regs, new_role);
shadow_mmu_init_context(vcpu, context, cpu_role, mmu_role);
kvm_mmu_new_pgd(vcpu, nested_cr3);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
Expand All @@ -4949,7 +4989,6 @@ kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
role.base.guest_mode = true;
role.base.access = ACC_ALL;

/* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */
role.ext.word = 0;
role.ext.execonly = execonly;
role.ext.valid = 1;
Expand All @@ -4963,12 +5002,14 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
{
struct kvm_mmu *context = &vcpu->arch.guest_mmu;
u8 level = vmx_eptp_page_walk_level(new_eptp);
union kvm_mmu_role new_role =
union kvm_mmu_role new_mode =
kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty,
execonly, level);

if (new_role.as_u64 != context->mmu_role.as_u64) {
context->mmu_role.as_u64 = new_role.as_u64;
if (new_mode.as_u64 != context->cpu_role.as_u64) {
/* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */
context->cpu_role.as_u64 = new_mode.as_u64;
context->mmu_role.as_u64 = new_mode.as_u64;

context->shadow_root_level = level;

Expand Down Expand Up @@ -5001,37 +5042,20 @@ static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
context->inject_page_fault = kvm_inject_page_fault;
}

static union kvm_mmu_role
kvm_calc_nested_mmu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
{
union kvm_mmu_role role;

role = kvm_calc_shadow_root_page_role_common(vcpu, regs);

/*
* Nested MMUs are used only for walking L2's gva->gpa, they never have
* shadow pages of their own and so "direct" has no meaning. Set it
* to "true" to try to detect bogus usage of the nested MMU.
*/
role.base.direct = true;
role.base.level = role_regs_to_root_level(regs);
return role;
}

static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
union kvm_mmu_role new_role = kvm_calc_nested_mmu_role(vcpu, regs);
union kvm_mmu_role new_mode = kvm_calc_cpu_role(vcpu, regs);
struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;

if (new_role.as_u64 == g_context->mmu_role.as_u64)
if (new_mode.as_u64 == g_context->cpu_role.as_u64)
return;

g_context->mmu_role.as_u64 = new_role.as_u64;
g_context->cpu_role.as_u64 = new_mode.as_u64;
g_context->get_guest_pgd = get_cr3;
g_context->get_pdptr = kvm_pdptr_read;
g_context->inject_page_fault = kvm_inject_page_fault;
g_context->root_level = new_role.base.level;
g_context->root_level = new_mode.base.level;

/*
* L2 page tables are never shadowed, so there is no need to sync
Expand Down Expand Up @@ -5089,6 +5113,9 @@ void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu)
vcpu->arch.root_mmu.mmu_role.ext.valid = 0;
vcpu->arch.guest_mmu.mmu_role.ext.valid = 0;
vcpu->arch.nested_mmu.mmu_role.ext.valid = 0;
vcpu->arch.root_mmu.cpu_role.ext.valid = 0;
vcpu->arch.guest_mmu.cpu_role.ext.valid = 0;
vcpu->arch.nested_mmu.cpu_role.ext.valid = 0;
kvm_mmu_reset_context(vcpu);

/*
Expand Down
2 changes: 1 addition & 1 deletion arch/x86/kvm/mmu/paging_tmpl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -281,7 +281,7 @@ static inline bool FNAME(is_last_gpte)(struct kvm_mmu *mmu,
* is not reserved and does not indicate a large page at this level,
* so clear PT_PAGE_SIZE_MASK in gpte if that is the case.
*/
gpte &= level - (PT32_ROOT_LEVEL + mmu->mmu_role.ext.cr4_pse);
gpte &= level - (PT32_ROOT_LEVEL + mmu->cpu_role.ext.cr4_pse);
#endif
/*
* PG_LEVEL_4K always terminates. The RHS has bit 7 set
Expand Down

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