diff mbox series

[2/2] KVM: xen: (re-)initialize shared_info if guest (32/64-bit) mode is set

Message ID 20231201104536.947-3-paul@xen.org
State New
Headers
Series KVM: xen: update shared_info when long_mode is set |

Commit Message

Paul Durrant Dec. 1, 2023, 10:45 a.m. UTC 
  From: Paul Durrant <pdurrant@amazon.com>

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
set. It is no lnger done when the PFN cache is activated.
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>
---
 arch/x86/kvm/xen.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Comments

Paul Durrant Dec. 1, 2023, 3:32 p.m. UTC | #1 
On 01/12/2023 10:45, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@amazon.com>
> 
> 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
> set. It is no lnger done when the PFN cache is activated.
> 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>
> ---
>   arch/x86/kvm/xen.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
> index 7bead3f65e55..bfc8f6698cbc 100644
> --- a/arch/x86/kvm/xen.c
> +++ b/arch/x86/kvm/xen.c
> @@ -624,8 +624,15 @@ 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;
>   
> @@ -657,9 +664,6 @@ 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;
>   	}
> @@ -1144,7 +1148,13 @@ 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)) {
> +		mutex_unlock(&kvm->arch.xen.xen_lock);

This unlock is bogus; it should have been removed. I'll send a v2.

   Paul

> +		return 1;
> +	}
>   
>   	/*
>   	 * If Xen hypercall intercept is enabled, fill the hypercall
diff mbox series

Patch

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 7bead3f65e55..bfc8f6698cbc 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -624,8 +624,15 @@  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;
 
@@ -657,9 +664,6 @@  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;
 	}
@@ -1144,7 +1148,13 @@  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)) {
+		mutex_unlock(&kvm->arch.xen.xen_lock);
+		return 1;
+	}
 
 	/*
 	 * If Xen hypercall intercept is enabled, fill the hypercall