FAILED: patch "[PATCH] KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said" failed to apply to 5.15-stable tree

PATCH New [email protected] 2 participants 3 messages Sep 29 – Sep 30

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Stable branch x86 KVM x86

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lore

[email protected]

author maintainer

2026-09-29 11:39 UTC #0 lore raw

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 10180a277549339020b08000206092c07e0bff5a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026092947-deflector-impound-8267@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 10180a277549339020b08000206092c07e0bff5a Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Mon, 21 Sep 2026 14:16:07 -0700
Subject: [PATCH] KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said
pages fails

Re-pend GET_NESTED_STATE_PAGES before exiting to userspace if getting the nested pages fails in the KVM_RUN path. If userspace re-runs the vCPU, and vmcs02 holds valid PFNs from the *previous* run of L2, then KVM could re-enter L2 with stale, unpinned PFNs mapped into e.g. the vAPIC page.

Note, both SVM and VMX (as of commit 11722439fb20 ("KVM: nVMX: Ensure KVM_REQ_GET_NESTED_STATE_PAGES is cleared on VM-Exit") ensure the request is cleared on VM-Exit (including the "forced" case), i.e. there is no risk of double-mapping due to emulated VMLAUNCH/VMRESUME/VMRUN *and* the request trying to map the nested pages.

Fixes 671ddc700fd0 ("KVM: nVMX: Don't leak L1 MMIO regions to L2")

Cc [email protected]

Reported-by Jinwoo Lee <[email protected]>

Closes https://lore.kernel.org/all/[email protected] open here

Reported-by Stefan Teodorescu <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Sean Christopherson <[email protected]>

arch/x86/kvm/x86.c +1 -0

index a137dc6dd8c6..4ec17aaff413 100644
@@ -8072,6 +8072,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 		if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
 			if (unlikely(!kvm_nested_call(get_nested_state_pages)(vcpu))) {
+				kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
 				r = 0;
 				goto out;
 			}

Sasha Levin

maintainer

2026-09-30 23:55 UTC #1 lore raw

PATCH 1/2 KVM: x86: Reject nested CAP enablement if nested virtualization is disabled

From: Sean Christopherson <[email protected]>

[ Upstream commit b65699be2c606d2687593516d93e66d16a713b61 ]

Add a flag to explicitly track if nested virtualization is enabled, and use it enumerate that various nested CAPs are unsupported, and to reject enablement of said CAPs. When the nested ops hooks were moved to their own structure, KVM's NULL-by-default behavior was deliberately dropped, with the changelog asserting that all was well. That wasn't quite true; there is no danger to KVM, but now KVM is over-reporting support for KVM_CAP_NESTED_STATE and KVM_CAP_HYPERV_ENLIGHTENED_VMCS.

Fixes 33b22172452f ("KVM: x86: move nested-related kvm_x86_ops to a separate struct")

Reviewed-by Vitaly Kuznetsov <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Sean Christopherson <[email protected]>

Backport notes for 5.15:
Keep svm_hardware_setup() in its existing location and initialize the nested flag after the existing EFER setup. Preserve the capability handler's function-scoped variables while adding the nested-enabled checks.

Provide kvm_nested_call() as a macro around the existing indirect hook and use it for get_nested_state_pages(). This preserves the current dispatch semantics without importing the later nested static-call conversion or adding any functions. Match the surrounding whitespace so that target 10180a277549339020b08000206092c07e0bff5a applies unchanged. The request re-pending fix itself remains in that target commit.

Stable-dep-of: 10180a277549 ("KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails")

Signed-off-by Sasha Levin <[email protected]>

---
 arch/x86/include/asm/kvm_host.h |  5 +++++
 arch/x86/kvm/hyperv.c           |  3 ++-
 arch/x86/kvm/svm/svm.c          |  1 +
 arch/x86/kvm/vmx/vmx.c          |  1 +
 arch/x86/kvm/x86.c              | 15 +++++++++------
 5 files changed, 18 insertions(+), 7 deletions(-)

arch/x86/include/asm/kvm_host.h +5 -0

index 710c9c87cdf2e..62012b9caa6e8 100644
@@ -1496,6 +1496,8 @@ struct kvm_x86_ops {
 };
 
 struct kvm_x86_nested_ops {
+	bool enabled;
+
 	void (*leave_nested)(struct kvm_vcpu *vcpu);
 	int (*check_events)(struct kvm_vcpu *vcpu);
 	bool (*hv_timer_pending)(struct kvm_vcpu *vcpu);

@@ -1537,6 +1539,9 @@ extern bool __read_mostly allow_smaller_maxphyaddr;
 extern bool __read_mostly enable_apicv;
 extern struct kvm_x86_ops kvm_x86_ops;
 
+/* Nested virtualization hooks use indirect calls. */
+#define kvm_nested_call(func) (kvm_x86_ops.nested_ops->func)
+
 #define KVM_X86_OP(func) \
 	DECLARE_STATIC_CALL(kvm_x86_##func, *(((struct kvm_x86_ops *)0)->func));
 #define KVM_X86_OP_NULL KVM_X86_OP

arch/x86/kvm/hyperv.c +2 -1

index 4e531036ab4c6..1ace566dac328 100644
@@ -2444,7 +2444,8 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 	};
 	int i, nent = ARRAY_SIZE(cpuid_entries);
 
-	if (kvm_x86_ops.nested_ops->get_evmcs_version)
+	if (kvm_x86_ops.nested_ops->enabled &&
+	    kvm_x86_ops.nested_ops->get_evmcs_version)
 		evmcs_ver = kvm_x86_ops.nested_ops->get_evmcs_version(vcpu);
 
 	/* Skip NESTED_FEATURES if eVMCS is not supported */

arch/x86/kvm/svm/svm.c +1 -0

index 16d2b697dc631..eca6733d080f6 100644
@@ -1017,6 +1017,7 @@ static __init int svm_hardware_setup(void)
 		printk(KERN_INFO "kvm: Nested Virtualization enabled\n");
 		kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE);
 	}
+	svm_nested_ops.enabled = nested;
 
 	/*
 	 * KVM's MMU doesn't support using 2-level paging for itself, and thus

arch/x86/kvm/vmx/vmx.c +1 -0

index 244b67601bce7..747f9086028bc 100644
@@ -8083,6 +8083,7 @@ static __init int hardware_setup(void)
 		if (r)
 			return r;
 	}
+	vmx_nested_ops.enabled = nested;
 
 	vmx_set_cpu_caps();

arch/x86/kvm/x86.c +9 -6

index bbfc8ccf4fcd9..30a9a9fd04aaa 100644
@@ -4236,14 +4236,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = KVM_X2APIC_API_VALID_FLAGS;
 		break;
 	case KVM_CAP_NESTED_STATE:
-		r = kvm_x86_ops.nested_ops->get_state ?
+		r = kvm_x86_ops.nested_ops->enabled ?
 			kvm_x86_ops.nested_ops->get_state(NULL, NULL, 0) : 0;
 		break;
 	case KVM_CAP_HYPERV_DIRECT_TLBFLUSH:
 		r = kvm_x86_ops.enable_direct_tlbflush != NULL;
 		break;
 	case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
-		r = kvm_x86_ops.nested_ops->enable_evmcs != NULL;
+		r = kvm_x86_ops.nested_ops->enabled &&
+		    kvm_x86_ops.nested_ops->enable_evmcs != NULL;
 		break;
 	case KVM_CAP_SMALLER_MAXPHYADDR:
 		r = (int) allow_smaller_maxphyaddr;

@@ -5081,7 +5082,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 		return kvm_hv_activate_synic(vcpu, cap->cap ==
 					     KVM_CAP_HYPERV_SYNIC2);
 	case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
-		if (!kvm_x86_ops.nested_ops->enable_evmcs)
+		if (!kvm_x86_ops.nested_ops->enabled ||
+		    !kvm_x86_ops.nested_ops->enable_evmcs)
 			return -ENOTTY;
 		r = kvm_x86_ops.nested_ops->enable_evmcs(vcpu, &vmcs_version);
 		if (!r) {

@@ -5411,7 +5413,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		u32 user_data_size;
 
 		r = -EINVAL;
-		if (!kvm_x86_ops.nested_ops->get_state)
+		if (!kvm_x86_ops.nested_ops->enabled)
 			break;
 
 		BUILD_BUG_ON(sizeof(user_data_size) != sizeof(user_kvm_nested_state->size));

@@ -5441,7 +5443,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		int idx;
 
 		r = -EINVAL;
-		if (!kvm_x86_ops.nested_ops->set_state)
+		if (!kvm_x86_ops.nested_ops->enabled)
 			break;
 
 		r = -EFAULT;

@@ -9774,8 +9776,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			r = -EIO;
 			goto out;
 		}
+
 		if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
-			if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) {
+			if (unlikely(!kvm_nested_call(get_nested_state_pages)(vcpu))) {
 				r = 0;
 				goto out;
 			}

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-30 23:55 UTC #2 lore raw

PATCH 2/2 KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails

From: Sean Christopherson <[email protected]>

[ Upstream commit 10180a277549339020b08000206092c07e0bff5a ]

Fixes 671ddc700fd0 ("KVM: nVMX: Don't leak L1 MMIO regions to L2")

Cc [email protected]

Reported-by Jinwoo Lee <[email protected]>

Closes https://lore.kernel.org/all/[email protected] open here

Reported-by Stefan Teodorescu <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Sean Christopherson <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 arch/x86/kvm/x86.c | 1 +
 1 file changed, 1 insertion(+)

arch/x86/kvm/x86.c +1 -0

index 30a9a9fd04aaa..c7a9203a60c96 100644
@@ -9779,6 +9779,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 		if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
 			if (unlikely(!kvm_nested_call(get_nested_state_pages)(vcpu))) {
+				kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
 				r = 0;
 				goto out;
 			}

Signature · 1 line

2.53.0