On Mon, Feb 27, 2023, Jeremi Piotrowski wrote:
> Disable TDP MMU when using SVM Hyper-V for the time being while we
> search for a better fix.
...
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c91ee2927dd7..5c0e28a7a3bc 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5787,14 +5787,15 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
> }
>
> void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
> - int tdp_max_root_level, int tdp_huge_page_level)
> + int tdp_max_root_level, int tdp_huge_page_level,
> + bool enable_tdp_mmu)
> {
> tdp_enabled = enable_tdp;
> tdp_root_level = tdp_forced_root_level;
> max_tdp_level = tdp_max_root_level;
>
> #ifdef CONFIG_X86_64
> - tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled;
> + tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled && enable_tdp_mmu;
> #endif
Thinking about this more, I would rather revert commit 1e0c7d40758b ("KVM: SVM:
hyper-v: Remote TLB flush for SVM") or fix the thing properly straitaway. KVM
doesn't magically handle the flushes correctly for the shadow/legacy MMU, KVM just
happens to get lucky and not run afoul of the underlying bugs. The revert appears
to be reasonably straightforward (see bottom).
And _if_ we want to hack-a-fix it, then I would strongly prefer a very isolated,
obviously hacky fix, e.g.
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 36e4561554ca..a9ba4ae14fda 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5779,8 +5779,13 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
tdp_root_level = tdp_forced_root_level;
max_tdp_level = tdp_max_root_level;
+ /*
+ * FIXME: Remove the enlightened TLB restriction when KVM properly
+ * handles TLB flushes for said enlightenment.
+ */.
#ifdef CONFIG_X86_64
- tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled;
+ tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled &&
+ !(ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB);
#endif
/*
* max_huge_page_level reflects KVM's MMU capabilities irrespective
The revert...
---
arch/x86/kvm/svm/svm.c | 3 ---
arch/x86/kvm/svm/svm_onhyperv.h | 27 ---------------------------
2 files changed, 30 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 11068e8eb969..292650dc85a0 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1320,7 +1320,6 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
if (sev_guest(vcpu->kvm))
sev_init_vmcb(svm);
- svm_hv_init_vmcb(vmcb);
init_vmcb_after_set_cpuid(vcpu);
vmcb_mark_all_dirty(vmcb);
@@ -4075,8 +4074,6 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
svm->vmcb->control.nested_cr3 = __sme_set(root_hpa);
vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
- hv_track_root_tdp(vcpu, root_hpa);
-
cr3 = vcpu->arch.cr3;
} else if (root_level >= PT64_ROOT_4LEVEL) {
cr3 = __sme_set(root_hpa) | kvm_get_active_pcid(vcpu);
diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
index 6981c1e9a809..5118fd273e73 100644
--- a/arch/x86/kvm/svm/svm_onhyperv.h
+++ b/arch/x86/kvm/svm/svm_onhyperv.h
@@ -15,31 +15,8 @@ static struct kvm_x86_ops svm_x86_ops;
int svm_hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu);
-static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
-{
- struct hv_vmcb_enlightenments *hve = &vmcb->control.hv_enlightenments;
-
- BUILD_BUG_ON(sizeof(vmcb->control.hv_enlightenments) !=
- sizeof(vmcb->control.reserved_sw));
-
- if (npt_enabled &&
- ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB)
- hve->hv_enlightenments_control.enlightened_npt_tlb = 1;
-
- if (ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)
- hve->hv_enlightenments_control.msr_bitmap = 1;
-}
-
static inline void svm_hv_hardware_setup(void)
{
- if (npt_enabled &&
- ms_hyperv.nested_features & HV_X64_NESTED_ENLIGHTENED_TLB) {
- pr_info(KBUILD_MODNAME ": Hyper-V enlightened NPT TLB flush enabled\n");
- svm_x86_ops.tlb_remote_flush = hv_remote_flush_tlb;
- svm_x86_ops.tlb_remote_flush_with_range =
- hv_remote_flush_tlb_with_range;
- }
-
if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH) {
int cpu;
@@ -80,10 +57,6 @@ static inline void svm_hv_update_vp_id(struct vmcb *vmcb, struct kvm_vcpu *vcpu)
}
#else
-static inline void svm_hv_init_vmcb(struct vmcb *vmcb)
-{
-}
-
static inline void svm_hv_hardware_setup(void)
{
}
base-commit: cb8748a781fe983e451f616ce4861a1c49ce79dd
--
