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FAILED: patch "[PATCH] KVM: SVM: Call SEV Guest Decommission if ASID binding fails" failed to apply to 5.10-stable tree

PATCH [email protected] 1 participant 1 message Jun 21, 2021

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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 <[email protected]>.

thanks,

greg k-h

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

From 934002cd660b035b926438244b4294e647507e13 Mon Sep 17 00:00:00 2001
From: Alper Gun <[email protected]>
Date: Thu, 10 Jun 2021 17:46:04 +0000
Subject: [PATCH] KVM: SVM: Call SEV Guest Decommission if ASID binding fails

Send SEV_CMD_DECOMMISSION command to PSP firmware if ASID binding fails. If a failure happens after a successful LAUNCH_START command, a decommission command should be executed. Otherwise, guest context will be unfreed inside the AMD SP. After the firmware will not have memory to allocate more SEV guest context, LAUNCH_START command will begin to fail with SEV_RET_RESOURCE_LIMIT error.

The existing code calls decommission inside sev_unbind_asid, but it is not called if a failure happens before guest activation succeeds. If sev_bind_asid fails, decommission is never called. PSP firmware has a limit for the number of guests. If sev_asid_binding fails many times, PSP firmware will not have resources to create another guest context.

Cc [email protected]
Fixes 59414c989220 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_START command")
Reported-by Peter Gonda <[email protected]>
Signed-off-by Alper Gun <[email protected]>
Reviewed-by Marc Orr <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>

Message-Id: <[email protected]>

arch/x86/kvm/svm/sev.c +15 -5
index e0ce5da97fc2..8d36f0c73071 100644
@@ -199,9 +199,19 @@ static void sev_asid_free(struct kvm_sev_info *sev)
 	sev->misc_cg = NULL;
 }
 
-static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
+static void sev_decommission(unsigned int handle)
 {
 	struct sev_data_decommission decommission;
+
+	if (!handle)
+		return;
+
+	decommission.handle = handle;
+	sev_guest_decommission(&decommission, NULL);
+}
+
+static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
+{
 	struct sev_data_deactivate deactivate;
 
 	if (!handle)

@@ -214,9 +224,7 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
 	sev_guest_deactivate(&deactivate, NULL);
 	up_read(&sev_deactivate_lock);
 
-	/* decommission handle */
-	decommission.handle = handle;
-	sev_guest_decommission(&decommission, NULL);
+	sev_decommission(handle);
 }
 
 static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)

@@ -341,8 +349,10 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	/* Bind ASID to this guest */
 	ret = sev_bind_asid(kvm, start.handle, error);
-	if (ret)
+	if (ret) {
+		sev_decommission(start.handle);
 		goto e_free_session;
+	}
 
 	/* return handle to userspace */
 	params.handle = start.handle;