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Subject[PATCH v3 6/9] x86/kvm/mmu: make space for source data caching in struct kvm_mmu
Date
In preparation to MMU reconfiguration avoidance we need a space to
cache source data. As this partially intersects with kvm_mmu_page_role,
create 64bit sized union kvm_mmu_role holding both base and extended data.
No functional change.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
Changes since v2:
- Use u32 for base_role instead of unsigned int in kvm_mmu_pte_write
[Sean Christopherson]
---
arch/x86/include/asm/kvm_host.h | 16 ++++++++++++++--
arch/x86/kvm/mmu.c | 28 +++++++++++++++++++++-------
arch/x86/kvm/vmx.c | 2 +-
3 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a64da200aed1..1821b0215230 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -247,7 +247,7 @@ struct kvm_mmu_memory_cache {
* @nxe, @cr0_wp, @smep_andnot_wp and @smap_andnot_wp.
*/
union kvm_mmu_page_role {
- unsigned word;
+ u32 word;
struct {
unsigned level:4;
unsigned cr4_pae:1;
@@ -273,6 +273,18 @@ union kvm_mmu_page_role {
};
};

+union kvm_mmu_extended_role {
+ u32 word;
+};
+
+union kvm_mmu_role {
+ u64 as_u64;
+ struct {
+ union kvm_mmu_page_role base;
+ union kvm_mmu_extended_role ext;
+ };
+};
+
struct kvm_rmap_head {
unsigned long val;
};
@@ -360,7 +372,7 @@ struct kvm_mmu {
void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
u64 *spte, const void *pte);
hpa_t root_hpa;
- union kvm_mmu_page_role base_role;
+ union kvm_mmu_role mmu_role;
u8 root_level;
u8 shadow_root_level;
u8 ept_ad;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 02bc3d6c27a3..60c916286bf4 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2359,7 +2359,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
int collisions = 0;
LIST_HEAD(invalid_list);

- role = vcpu->arch.mmu->base_role;
+ role = vcpu->arch.mmu->mmu_role.base;
role.level = level;
role.direct = direct;
if (role.direct)
@@ -4407,7 +4407,8 @@ static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
void
reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
{
- bool uses_nx = context->nx || context->base_role.smep_andnot_wp;
+ bool uses_nx = context->nx ||
+ context->mmu_role.base.smep_andnot_wp;
struct rsvd_bits_validate *shadow_zero_check;
int i;

@@ -4726,7 +4727,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *context = vcpu->arch.mmu;

- context->base_role.word = mmu_base_role_mask.word &
+ context->mmu_role.base.word = mmu_base_role_mask.word &
kvm_calc_tdp_mmu_root_page_role(vcpu).word;
context->page_fault = tdp_page_fault;
context->sync_page = nonpaging_sync_page;
@@ -4807,7 +4808,7 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
else
paging32_init_context(vcpu, context);

- context->base_role.word = mmu_base_role_mask.word &
+ context->mmu_role.base.word = mmu_base_role_mask.word &
kvm_calc_shadow_mmu_root_page_role(vcpu).word;
reset_shadow_zero_bits_mask(vcpu, context);
}
@@ -4816,7 +4817,7 @@ EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
static union kvm_mmu_page_role
kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty)
{
- union kvm_mmu_page_role role = vcpu->arch.mmu->base_role;
+ union kvm_mmu_page_role role = vcpu->arch.mmu->mmu_role.base;

/* Role is inherited from root_mmu */
role.word = vcpu->arch.root_mmu.base_role.word;
@@ -4849,7 +4850,8 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
context->update_pte = ept_update_pte;
context->root_level = PT64_ROOT_4LEVEL;
context->direct_map = false;
- context->base_role.word = root_page_role.word & mmu_base_role_mask.word;
+ context->mmu_role.base.word =
+ root_page_role.word & mmu_base_role_mask.word;

update_permission_bitmask(vcpu, context, true);
update_pkru_bitmask(vcpu, context, true);
@@ -5163,10 +5165,12 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,

local_flush = true;
while (npte--) {
+ u32 base_role = vcpu->arch.mmu->mmu_role.base.word;
+
entry = *spte;
mmu_page_zap_pte(vcpu->kvm, sp, spte);
if (gentry &&
- !((sp->role.word ^ vcpu->arch.mmu->base_role.word)
+ !((sp->role.word ^ base_role)
& mmu_base_role_mask.word) && rmap_can_add(vcpu))
mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);
if (need_remote_flush(entry, *spte))
@@ -5863,6 +5867,16 @@ int kvm_mmu_module_init(void)
{
int ret = -ENOMEM;

+ /*
+ * MMU roles use union aliasing which is, generally speaking, an
+ * undefined behavior. However, we supposedly know how compilers behave
+ * and the current status quo is unlikely to change. Guardians below are
+ * supposed to let us know if the assumption becomes false.
+ */
+ BUILD_BUG_ON(sizeof(union kvm_mmu_page_role) != sizeof(u32));
+ BUILD_BUG_ON(sizeof(union kvm_mmu_extended_role) != sizeof(u32));
+ BUILD_BUG_ON(sizeof(union kvm_mmu_role) != sizeof(u64));
+
kvm_mmu_reset_all_pte_masks();

pte_list_desc_cache = kmem_cache_create("pte_list_desc",
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 73f04a8638d3..c4ad4e84b898 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9321,7 +9321,7 @@ static int nested_vmx_eptp_switching(struct kvm_vcpu *vcpu,

kvm_mmu_unload(vcpu);
mmu->ept_ad = accessed_dirty;
- mmu->base_role.ad_disabled = !accessed_dirty;
+ mmu->mmu_role.base.ad_disabled = !accessed_dirty;
vmcs12->ept_pointer = address;
/*
* TODO: Check what's the correct approach in case
--
2.17.1
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