From: Paul Durrant <pdurrant@amazon.com>
Date: Wed, 8 Nov 2023 10:06:33 +0000 (+0000)
Subject: KVM: xen: (re-)initialize shared_info if guest (32/64-bit) mode is set
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f1a72f58ae411709a32aa033ce1a3e4f9be7b91d;p=people%2Fpauldu%2Flinux.git

KVM: xen: (re-)initialize shared_info if guest (32/64-bit) mode is set

If the shared_info PFN cache has already been initialized then the content
of the shared_info page needs to be (re-)initialized if the guest mode is
(re)set.
Setting the guest mode is either done explicitly by the VMM via the
KVM_XEN_ATTR_TYPE_LONG_MODE attribute, or implicitly when the guest writes
the MSR to set up the hypercall page.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: x86@kernel.org

v10:
 - New in this version.
---

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9351b32cfcba..6a56be78649c 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -625,8 +625,15 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 		} else {
 			mutex_lock(&kvm->arch.xen.xen_lock);
 			kvm->arch.xen.long_mode = !!data->u.long_mode;
+
+			/*
+			 * If shared_info has already been initialized
+			 * then re-initialize it with the new width.
+			 */
+			r = kvm->arch.xen.shinfo_cache.active ?
+				kvm_xen_shared_info_init(kvm) : 0;
+
 			mutex_unlock(&kvm->arch.xen.xen_lock);
-			r = 0;
 		}
 		break;
 
@@ -648,9 +655,6 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 
 		srcu_read_unlock(&kvm->srcu, idx);
 
-		if (!r && kvm->arch.xen.shinfo_cache.active)
-			r = kvm_xen_shared_info_init(kvm);
-
 		mutex_unlock(&kvm->arch.xen.xen_lock);
 		break;
 	}
@@ -1103,7 +1107,11 @@ int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
 	bool lm = is_long_mode(vcpu);
 
 	/* Latch long_mode for shared_info pages etc. */
-	vcpu->kvm->arch.xen.long_mode = lm;
+	kvm->arch.xen.long_mode = lm;
+
+	if (kvm->arch.xen.shinfo_cache.active &&
+	    kvm_xen_shared_info_init(kvm))
+		return 1;
 
 	/*
 	 * If Xen hypercall intercept is enabled, fill the hypercall