FAILED: patch "[PATCH] KVM: nSVM: Add missing consistency check for nCR3 validity" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x b71138fcc362c67ebe66747bb22cb4e6b4d6a651
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026050328-conduit-posing-1921@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From b71138fcc362c67ebe66747bb22cb4e6b4d6a651 Mon Sep 17 00:00:00 2001
From: Yosry Ahmed <yosry@kernel.org>
Date: Tue, 3 Mar 2026 00:34:09 +0000
Subject: [PATCH] KVM: nSVM: Add missing consistency check for nCR3 validity
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From the APM Volume #2, 15.25.4 (24593—Rev. 3.42—March 2024):

  When VMRUN is executed with nested paging enabled (NP_ENABLE = 1), the
  following conditions are considered illegal state combinations, in
  addition to those mentioned in “Canonicalization and Consistency Checks”:
      • Any MBZ bit of nCR3 is set.
      • Any G_PAT.PA field has an unsupported type encoding or any
        reserved field in G_PAT has a nonzero value.

Add the consistency check for nCR3 being a legal GPA with no MBZ bits
set.  Note, the G_PAT.PA check is being handled separately[*].

Link: https://lore.kernel.org/kvm/20260205214326.1029278-3-jmattson@google.com [*]
Fixes: 4b16184c1cca ("KVM: SVM: Initialize Nested Nested MMU context on VMRUN")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-16-yosry@kernel.org
[sean: capture everything in CC(), massage changelog formatting]
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 2ed6530e7bd1..a59b976c16db 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -348,6 +348,10 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 	if (CC(control->asid == 0))
 		return false;
 
+	if (CC((control->nested_ctl & SVM_NESTED_CTL_NP_ENABLE) &&
+	       !kvm_vcpu_is_legal_gpa(vcpu, control->nested_cr3)))
+		return false;
+
 	if (CC(!nested_svm_check_bitmap_pa(vcpu, control->msrpm_base_pa,
 					   MSRPM_SIZE)))
 		return false;