[PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level

Wei Huang
2021-08-08T19:27:23Z

AMD future CPUs will require a 5-level NPT if host CR4.LA57 is set.
To prevent kvm_mmu_get_tdp_level() from incorrectly changing NPT level
on behalf of CPUs, add a new parameter in kvm_configure_mmu() to force
a fixed TDP level.

Signed-off-by: Wei Huang <wei.huang2@amd.com>
---
arch/x86/include/asm/kvm_host.h | 5 ++---
arch/x86/kvm/mmu/mmu.c | 10 ++++++++--
arch/x86/kvm/svm/svm.c | 4 +++-
arch/x86/kvm/vmx/vmx.c | 3 ++-
4 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 974cbfb1eefe..6d16f75cc8da 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -723,7 +723,6 @@ struct kvm_vcpu_arch {

u64 reserved_gpa_bits;
int maxphyaddr;
- int max_tdp_level;

/* emulate context */

@@ -1747,8 +1746,8 @@ void kvm_mmu_invalidate_gva(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid);
void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd);

-void kvm_configure_mmu(bool enable_tdp, int tdp_max_root_level,
- int tdp_huge_page_level);
+void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
+ int tdp_max_root_level, int tdp_huge_page_level);

static inline u16 kvm_read_ldt(void)
{
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 66f7f5bc3482..c11ee4531f6d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -97,6 +97,7 @@ module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644);
bool tdp_enabled = false;

static int max_huge_page_level __read_mostly;
+static int tdp_root_level __read_mostly;
static int max_tdp_level __read_mostly;

enum {
@@ -4562,6 +4563,10 @@ static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,

static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
{
+ /* tdp_root_level is architecture forced level, use it if nonzero */
+ if (tdp_root_level)
+ return tdp_root_level;
+
/* Use 5-level TDP if and only if it's useful/necessary. */
if (max_tdp_level == 5 && cpuid_maxphyaddr(vcpu) <= 48)
return 4;
@@ -5253,10 +5258,11 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
*/
}

-void kvm_configure_mmu(bool enable_tdp, int tdp_max_root_level,
- int tdp_huge_page_level)
+void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
+ int tdp_max_root_level, int tdp_huge_page_level)
{
tdp_enabled = enable_tdp;
+ tdp_root_level = tdp_forced_root_level;
max_tdp_level = tdp_max_root_level;

/*
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e8ccab50ebf6..f361d466e18e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1015,7 +1015,9 @@ static __init int svm_hardware_setup(void)
if (!boot_cpu_has(X86_FEATURE_NPT))
npt_enabled = false;

- kvm_configure_mmu(npt_enabled, get_max_npt_level(), PG_LEVEL_1G);
+ /* Force VM NPT level equal to the host's max NPT level */
+ kvm_configure_mmu(npt_enabled, get_max_npt_level(),
+ get_max_npt_level(), PG_LEVEL_1G);
pr_info("kvm: Nested Paging %sabled\n", npt_enabled ? "en" : "dis");

/* Note, SEV setup consumes npt_enabled. */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 927a552393b9..034e1397c7d5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7803,7 +7803,8 @@ static __init int hardware_setup(void)
ept_lpage_level = PG_LEVEL_2M;
else
ept_lpage_level = PG_LEVEL_4K;
- kvm_configure_mmu(enable_ept, vmx_get_max_tdp_level(), ept_lpage_level);
+ kvm_configure_mmu(enable_ept, 0, vmx_get_max_tdp_level(),
+ ept_lpage_level);

/*
* Only enable PML when hardware supports PML feature, and both EPT
--
2.31.1