On 12/19/2023 11:26 PM, Sean Christopherson wrote:
KVM can simply
constrain the advertised MAXPHYADDR, no?
Sean. It looks you agree with this patch (Patch 1) now.
I think it's better for you to comment the original code from Tao
instead of throwing out your own version. Tao needs to know why his
version is not OK/correct and what can be improved.
Thanks,
-Xiaoyao
---
arch/x86/kvm/cpuid.c | 17 +++++++++++++----
arch/x86/kvm/mmu.h | 2 ++
arch/x86/kvm/mmu/mmu.c | 5 +++++
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 294e5bd5f8a0..5c346e1a10bd 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1233,12 +1233,21 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
*
* If TDP is enabled but an explicit guest MAXPHYADDR is not
* provided, use the raw bare metal MAXPHYADDR as reductions to
- * the HPAs do not affect GPAs.
+ * the HPAs do not affect GPAs. Finally, if TDP is enabled and
+ * doesn't support 5-level paging, cap guest MAXPHYADDR at 48
+ * bits as KVM can't install SPTEs for larger GPAs.
*/
- if (!tdp_enabled)
+ if (!tdp_enabled) {
g_phys_as = boot_cpu_data.x86_phys_bits;
- else if (!g_phys_as)
- g_phys_as = phys_as;
+ } else {
+ u8 max_tdp_level = kvm_mmu_get_max_tdp_level();
+
+ if (!g_phys_as)
+ g_phys_as = phys_as;
+
+ if (max_tdp_level < 5)
+ g_phys_as = min(g_phys_as, 48);
+ }
entry->eax = g_phys_as | (virt_as << 8);
entry->ecx &= ~(GENMASK(31, 16) | GENMASK(11, 8));
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 60f21bb4c27b..b410a227c601 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -100,6 +100,8 @@ static inline u8 kvm_get_shadow_phys_bits(void)
return boot_cpu_data.x86_phys_bits;
}
+u8 kvm_mmu_get_max_tdp_level(void);
+
void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask);
void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 3c844e428684..b2845f5520b3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5267,6 +5267,11 @@ static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
return max_tdp_level;
}
+u8 kvm_mmu_get_max_tdp_level(void)
+{
+ return tdp_root_level ? tdp_root_level : max_tdp_level;
+}
+
static union kvm_mmu_page_role
kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
union kvm_cpu_role cpu_role)
base-commit: f2a3fb7234e52f72ff4a38364dbf639cf4c7d6c6
--
