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* FAILED: patch "[PATCH] KVM: x86: Fill kvm_run exit fields in common" failed to apply to 6.18-stable tree
@ 2026-09-29 11:38 gregkh
  2026-09-30 15:39 ` [PATCH 6.18.y 1/4] KVM: move TSS constants from kvm_host.h to tss.h Sasha Levin
  0 siblings, 1 reply; 6+ messages in thread
From: gregkh @ 2026-09-29 11:38 UTC (permalink / raw)
  To: seanjc, fane, rkskek9254; +Cc: stable


The patch below does not apply to the 6.18-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 <stable@vger.kernel.org>.

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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x c1214f293d77c6e425a379f90d09bdb4815993a8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092938-celibate-sarcastic-e56f@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From c1214f293d77c6e425a379f90d09bdb4815993a8 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Mon, 21 Sep 2026 14:16:08 -0700
Subject: [PATCH] KVM: x86: Fill kvm_run exit fields in common
 get_nested_state_pages() error paths

Fill kvm_run with "internal error, emulation" in the common error handling
paths for getting nested state pages, as requiring each check to manually
fill kvm_run is error prone and requires a non-trivial amount of copy+paste.

Specifically, both SVM and VMX fail to fill kvm_run if load_pdptrs() fails,
and SVM fails to fill kvm_run if kvm_hv_verify_vp_assist() fails.  If those
flows fail, the *best* case scenario is that KVM will exit to userspace
with KVM_EXIT_UNKNOWN.  The worst case scenario is that KVM exits with a
stale exit_reason and confuses userspace.

Note, SVM never exits to userspace if something goes sideways when dealing
with vmcb12 assets while emulating VMRUN, i.e. lack of SVM-specific code is
not a bug.

Fixes: 0f85722341b0 ("KVM: nVMX: delay loading of PDPTRs to KVM_REQ_GET_NESTED_STATE_PAGES")
Fixes: 232f75d3b4b5 ("KVM: nSVM: call nested_svm_load_cr3 on nested state load")
Fixes: 3f4a812edf5c ("KVM: nSVM: hyper-v: Enable L2 TLB flush")
Cc: stable@vger.kernel.org
Reported-by: Jinwoo Lee <rkskek9254@gmail.com>
Closes: https://lore.kernel.org/all/20260813043932.3214460-1-rkskek9254@gmail.com
Reported-by: Stefan Teodorescu <fane@google.com>
Link: https://patch.msgid.link/20260921211608.1030158-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 73f37b050d0a..f9090b601efa 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -2125,13 +2125,8 @@ static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
 			return false;
 	}
 
-	if (!nested_svm_merge_msrpm(vcpu)) {
-		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-		vcpu->run->internal.suberror =
-			KVM_INTERNAL_ERROR_EMULATION;
-		vcpu->run->internal.ndata = 0;
+	if (!nested_svm_merge_msrpm(vcpu))
 		return false;
-	}
 
 	if (kvm_hv_verify_vp_assist(vcpu))
 		return false;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 151873407abd..40c1a5f6fa8a 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3465,10 +3465,6 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 		} else {
 			pr_debug_ratelimited("%s: no backing for APIC-access address in vmcs12\n",
 					     __func__);
-			vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-			vcpu->run->internal.suberror =
-				KVM_INTERNAL_ERROR_EMULATION;
-			vcpu->run->internal.ndata = 0;
 			return false;
 		}
 	}
@@ -3539,11 +3535,6 @@ static bool vmx_get_nested_state_pages(struct kvm_vcpu *vcpu)
 	if (!nested_get_evmcs_page(vcpu)) {
 		pr_debug_ratelimited("%s: enlightened vmptrld failed\n",
 				     __func__);
-		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
-		vcpu->run->internal.suberror =
-			KVM_INTERNAL_ERROR_EMULATION;
-		vcpu->run->internal.ndata = 0;
-
 		return false;
 	}
 #endif
@@ -3915,8 +3906,12 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 
 vmentry_failed:
 	vcpu->arch.nested_run_pending = 0;
-	if (status == NVMX_VMENTRY_KVM_INTERNAL_ERROR)
+	if (status == NVMX_VMENTRY_KVM_INTERNAL_ERROR) {
+		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+		vcpu->run->internal.ndata = 0;
 		return 0;
+	}
 	if (status == NVMX_VMENTRY_VMEXIT)
 		return 1;
 	WARN_ON_ONCE(status != NVMX_VMENTRY_VMFAIL);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4ec17aaff413..aad065d035fb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8072,6 +8072,9 @@ 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))) {
+				vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+				vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+				vcpu->run->internal.ndata = 0;
 				kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
 				r = 0;
 				goto out;


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-10-07  6:42 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-29 11:38 FAILED: patch "[PATCH] KVM: x86: Fill kvm_run exit fields in common" failed to apply to 6.18-stable tree gregkh
2026-09-30 15:39 ` [PATCH 6.18.y 1/4] KVM: move TSS constants from kvm_host.h to tss.h Sasha Levin
2026-09-30 15:39   ` [PATCH 6.18.y 2/4] KVM: x86: Reject nested CAP enablement if nested virtualization is disabled Sasha Levin
2026-09-30 15:39   ` [PATCH 6.18.y 3/4] KVM: x86: Add static calls for nested virtualization ops Sasha Levin
2026-09-30 15:39   ` [PATCH 6.18.y 4/4] KVM: x86: Fill kvm_run exit fields in common get_nested_state_pages() error paths Sasha Levin
2026-10-07  6:40     ` Greg KH

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