FAILED: patch "[PATCH] KVM: x86: Reinitialize context if host userspace toggles" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-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]>.

thanks,

greg k-h

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

From d6174299365ddbbf491620c0b8c5ca1a6ef2eea5 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <[email protected]>
Date: Wed, 9 Feb 2022 04:56:05 -0500
Subject: [PATCH] KVM: x86: Reinitialize context if host userspace toggles
EFER.LME

While the guest runs, EFER.LME cannot change unless CR0.PG is clear, and therefore EFER.NX is the only bit that can affect the MMU role. However, set_efer accepts a host-initiated change to EFER.LME even with CR0.PG=1. In that case, the MMU has to be reset.

index 51faa2c76ca5..a5a50cfeffff 100644
@@ -48,6 +48,7 @@
 			       X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE)
 
 #define KVM_MMU_CR0_ROLE_BITS (X86_CR0_PG | X86_CR0_WP)
+#define KVM_MMU_EFER_ROLE_BITS (EFER_LME | EFER_NX)
 
 static __always_inline u64 rsvd_bits(int s, int e)
 {

index 0b95c379e234..b724273493d8 100644
@@ -1648,8 +1648,7 @@ static int set_efer(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		return r;
 	}
 
-	/* Update reserved bits */
-	if ((efer ^ old_efer) & EFER_NX)
+	if ((efer ^ old_efer) & KVM_MMU_EFER_ROLE_BITS)
 		kvm_mmu_reset_context(vcpu);
 
 	return 0;