This is a note to let you know that I've just added the patch titled
KVM: x86/mmu: Fully re-evaluate MMIO caching when SPTE masks change
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-mmu-fully-re-evaluate-mmio-caching-when-spte-masks-change.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c3e0c8c2e8b17bae30d5978bc2decdd4098f0f99 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Wed, 3 Aug 2022 22:49:56 +0000
Subject: KVM: x86/mmu: Fully re-evaluate MMIO caching when SPTE masks change
From: Sean Christopherson <seanjc@xxxxxxxxxx>
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@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Tested-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
Message-Id: <20220803224957.1285926-3-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are
queue-5.19/kvm-x86-mmu-treat-nx-as-a-valid-spte-bit-for-npt.patch
queue-5.19/kvm-x86-xen-initialize-xen-timer-only-once.patch
queue-5.19/kvm-x86-tag-kvm_mmu_x86_module_init-with-__init.patch
queue-5.19/kvm-x86-xen-stop-xen-timer-before-changing-irq.patch
queue-5.19/kvm-put-the-extra-pfn-reference-when-reusing-a-pfn-in-the-gpc-cache.patch
queue-5.19/kvm-drop-unused-gpa-param-from-gfn-pfn-cache-s-__release_gpc-helper.patch
queue-5.19/kvm-nvmx-let-userspace-set-nvmx-msr-to-any-_host_-supported-value.patch
queue-5.19/kvm-svm-disable-sev-es-support-if-mmio-caching-is-disable.patch
queue-5.19/kvm-x86-mmu-fully-re-evaluate-mmio-caching-when-spte-masks-change.patch
queue-5.19/kvm-x86-set-error-code-to-segment-selector-on-lldt-ltr-non-canonical-gp.patch
queue-5.19/kvm-nvmx-inject-ud-if-vmxon-is-attempted-with-incompatible-cr0-cr4.patch
queue-5.19/kvm-do-not-incorporate-page-offset-into-gfn-pfn-cache-user-address.patch
queue-5.19/kvm-svm-don-t-bug-if-userspace-injects-an-interrupt-with-gif-0.patch
queue-5.19/kvm-nvmx-snapshot-pre-vm-enter-bndcfgs-for-nested_run_pending-case.patch
queue-5.19/kvm-x86-split-kvm_is_valid_cr4-and-export-only-the-non-vendor-bits.patch
queue-5.19/kvm-fix-multiple-races-in-gfn-pfn-cache-refresh.patch
queue-5.19/kvm-fully-serialize-gfn-pfn-cache-refresh-via-mutex.patch
queue-5.19/kvm-x86-mark-tss-busy-during-ltr-emulation-_after_-all-fault-checks.patch
queue-5.19/kvm-nvmx-account-for-kvm-reserved-cr4-bits-in-consistency-checks.patch
queue-5.19/kvm-nvmx-snapshot-pre-vm-enter-debugctl-for-nested_run_pending-case.patch
