From: Sean Christopherson seanjc@google.com
commit c3e0c8c2e8b17bae30d5978bc2decdd4098f0f99 upstream.
Fully re-evaluate whether or not MMIO caching can be enabled when SPTE masks change; simply clearing enable_mmio_caching when a configuration isn't compatible with caching fails to handle the scenario where the masks are updated, e.g. by VMX for EPT or by SVM to account for the C-bit location, and toggle compatibility from false=>true.
Snapshot the original module param so that re-evaluating MMIO caching preserves userspace's desire to allow caching. Use a snapshot approach so that enable_mmio_caching still reflects KVM's actual behavior.
Fixes: 8b9e74bfbf8c ("KVM: x86/mmu: Use enable_mmio_caching to track if MMIO caching is enabled") Reported-by: Michael Roth michael.roth@amd.com Cc: Tom Lendacky thomas.lendacky@amd.com Cc: stable@vger.kernel.org Tested-by: Michael Roth michael.roth@amd.com Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Kai Huang kai.huang@intel.com Message-Id: 20220803224957.1285926-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/mmu/mmu.c | 4 ++++ arch/x86/kvm/mmu/spte.c | 19 +++++++++++++++++++ arch/x86/kvm/mmu/spte.h | 1 + 3 files changed, 24 insertions(+)
--- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -6274,11 +6274,15 @@ static int set_nx_huge_pages(const char /* * nx_huge_pages needs to be resolved to true/false when kvm.ko is loaded, as * its default value of -1 is technically undefined behavior for a boolean. + * Forward the module init call to SPTE code so that it too can handle module + * params that need to be resolved/snapshot. */ void __init kvm_mmu_x86_module_init(void) { if (nx_huge_pages == -1) __set_nx_huge_pages(get_nx_auto_mode()); + + kvm_mmu_spte_module_init(); }
/* --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -20,6 +20,7 @@ #include <asm/vmx.h>
bool __read_mostly enable_mmio_caching = true; +static bool __ro_after_init allow_mmio_caching; module_param_named(mmio_caching, enable_mmio_caching, bool, 0444); EXPORT_SYMBOL_GPL(enable_mmio_caching);
@@ -43,6 +44,18 @@ u64 __read_mostly shadow_nonpresent_or_r
u8 __read_mostly shadow_phys_bits;
+void __init kvm_mmu_spte_module_init(void) +{ + /* + * Snapshot userspace's desire to allow MMIO caching. Whether or not + * KVM can actually enable MMIO caching depends on vendor-specific + * hardware capabilities and other module params that can't be resolved + * until the vendor module is loaded, i.e. enable_mmio_caching can and + * will change when the vendor module is (re)loaded. + */ + allow_mmio_caching = enable_mmio_caching; +} + static u64 generation_mmio_spte_mask(u64 gen) { u64 mask; @@ -338,6 +351,12 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio BUG_ON((u64)(unsigned)access_mask != access_mask); WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
+ /* + * Reset to the original module param value to honor userspace's desire + * to (dis)allow MMIO caching. Update the param itself so that + * userspace can see whether or not KVM is actually using MMIO caching. + */ + enable_mmio_caching = allow_mmio_caching; if (!enable_mmio_caching) mmio_value = 0;
--- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -444,6 +444,7 @@ static inline u64 restore_acc_track_spte
u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn);
+void __init kvm_mmu_spte_module_init(void); void kvm_mmu_reset_all_pte_masks(void);
#endif