[PATCH v2 08/25] KVM: x86/mmu: split cpu_mode from mmu_role

Paolo Bonzini
2022-02-21T16:23:12Z

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 mode; and in fact the new function
kvm_calc_cpu_mode is analogous to the previous kvm_calc_nested_mmu_role,
except that it has role.base.direct equal to CR0.PG. It is not clear
what the code meant by "setting role.base.direct to true to detect bogus
usage of the nested MMU".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu/mmu.c | 107 ++++++++++++++++++++------------
arch/x86/kvm/mmu/paging_tmpl.h | 2 +-
3 files changed, 68 insertions(+), 42 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 92855d3984a7..cc268116eb3f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -433,6 +433,7 @@ 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_mode;
union kvm_mmu_role mmu_role;
u8 root_level;
u8 shadow_root_level;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7c835253a330..1af898f0cf87 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -221,7 +221,7 @@ 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_mode. base_or_ext . reg##_##name); \
}
BUILD_MMU_ROLE_ACCESSOR(ext, cr0, pg);
BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
@@ -4680,6 +4680,39 @@ static void paging32_init_context(struct kvm_mmu *context)
context->direct_map = false;
}

+static union kvm_mmu_role
+kvm_calc_cpu_mode(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.base.direct = !____is_cr0_pg(regs);
+ if (!role.base.direct) {
+ 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);
+ }
+
+ role.ext.valid = 1;
+ return role;
+}
+
static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
const struct kvm_mmu_role_regs *regs)
{
@@ -4739,13 +4772,16 @@ 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_mode = kvm_calc_cpu_mode(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_mode.as_u64 == context->cpu_mode.as_u64 &&
+ mmu_role.as_u64 == context->mmu_role.as_u64)
return;

- context->mmu_role.as_u64 = new_role.as_u64;
+ context->cpu_mode.as_u64 = cpu_mode.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;
@@ -4800,13 +4836,15 @@ 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_mode,
+ union kvm_mmu_role mmu_role)
{
- if (new_role.as_u64 == context->mmu_role.as_u64)
+ if (cpu_mode.as_u64 == context->cpu_mode.as_u64 &&
+ mmu_role.as_u64 == context->mmu_role.as_u64)
return;

- context->mmu_role.as_u64 = new_role.as_u64;
+ context->cpu_mode.as_u64 = cpu_mode.as_u64;
+ context->mmu_role.as_u64 = mmu_role.as_u64;

if (!is_cr0_pg(context))
nonpaging_init_context(context);
@@ -4814,10 +4852,10 @@ static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *conte
paging64_init_context(context);
else
paging32_init_context(context);
- context->root_level = role_regs_to_root_level(regs);
+ context->root_level = cpu_mode.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);
}
@@ -4826,10 +4864,11 @@ 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_mode = kvm_calc_cpu_mode(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_mode, mmu_role);
}

static union kvm_mmu_role
@@ -4854,11 +4893,10 @@ 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;
+ union kvm_mmu_role cpu_mode = kvm_calc_cpu_mode(vcpu, &regs);
+ union kvm_mmu_role mmu_role = kvm_calc_shadow_npt_root_page_role(vcpu, &regs);;

- new_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_mode, mmu_role);
kvm_mmu_new_pgd(vcpu, nested_cr3);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
@@ -4881,7 +4919,6 @@ 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;
@@ -4895,12 +4932,14 @@ 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_mode.as_u64) {
+ /* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */
+ context->cpu_mode.as_u64 = new_mode.as_u64;
+ context->mmu_role.as_u64 = new_mode.as_u64;

context->shadow_root_level = level;

@@ -4933,36 +4972,19 @@ static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
context->inject_page_fault = kvm_inject_page_fault_shadow;
}

-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_mode(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_mode.as_u64)
return;

- g_context->mmu_role.as_u64 = new_role.as_u64;
+ g_context->cpu_mode.as_u64 = new_mode.as_u64;
g_context->get_guest_pgd = kvm_get_guest_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
@@ -5020,6 +5042,9 @@ 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_mode.ext.valid = 0;
+ vcpu->arch.guest_mmu.cpu_mode.ext.valid = 0;
+ vcpu->arch.nested_mmu.cpu_mode.ext.valid = 0;
kvm_mmu_reset_context(vcpu);

/*
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index d1d17d28e81b..e1c2ecb4ddee 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -323,7 +323,7 @@ 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_mode.ext.cr4_pse);
#endif
/*
* PG_LEVEL_4K always terminates. The RHS has bit 7 set
--
2.31.1