linux-kernel - [PATCH 1/6] KVM: SEV: use mutex guard in snp_launch

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Message-ID: <20251219114238.3797364-2-clopez@suse.de>
Date: Fri, 19 Dec 2025 12:41:56 +0100
From: Carlos López <clopez@...e.de>
To: kvm@...r.kernel.org,
	seanjc@...gle.com,
	pbonzini@...hat.com
Cc: tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	hpa@...or.com,
	linux-kernel@...r.kernel.org,
	Carlos López <clopez@...e.de>
Subject: [PATCH 1/6] KVM: SEV: use mutex guard in snp_launch_update()

Simplify the error paths in snp_launch_update() by using a mutex guard,
allowing early return instead of using gotos.

Signed-off-by: Carlos López <clopez@...e.de>
---
 arch/x86/kvm/svm/sev.c | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index f59c65abe3cf..1b325ae61d15 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -8,6 +8,7 @@
  */
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/cleanup.h>
 #include <linux/kvm_types.h>
 #include <linux/kvm_host.h>
 #include <linux/kernel.h>
@@ -2367,7 +2368,6 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	struct kvm_memory_slot *memslot;
 	long npages, count;
 	void __user *src;
-	int ret = 0;
 
 	if (!sev_snp_guest(kvm) || !sev->snp_context)
 		return -EINVAL;
@@ -2407,13 +2407,11 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	 * initial expected state and better guard against unexpected
 	 * situations.
 	 */
-	mutex_lock(&kvm->slots_lock);
+	guard(mutex)(&kvm->slots_lock);
 
 	memslot = gfn_to_memslot(kvm, params.gfn_start);
-	if (!kvm_slot_has_gmem(memslot)) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (!kvm_slot_has_gmem(memslot))
+		return -EINVAL;
 
 	sev_populate_args.sev_fd = argp->sev_fd;
 	sev_populate_args.type = params.type;
@@ -2425,22 +2423,18 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		argp->error = sev_populate_args.fw_error;
 		pr_debug("%s: kvm_gmem_populate failed, ret %ld (fw_error %d)\n",
 			 __func__, count, argp->error);
-		ret = -EIO;
-	} else {
-		params.gfn_start += count;
-		params.len -= count * PAGE_SIZE;
-		if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO)
-			params.uaddr += count * PAGE_SIZE;
-
-		ret = 0;
-		if (copy_to_user(u64_to_user_ptr(argp->data), &params, sizeof(params)))
-			ret = -EFAULT;
+		return -EIO;
 	}
 
-out:
-	mutex_unlock(&kvm->slots_lock);
+	params.gfn_start += count;
+	params.len -= count * PAGE_SIZE;
+	if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO)
+		params.uaddr += count * PAGE_SIZE;
 
-	return ret;
+	if (copy_to_user(u64_to_user_ptr(argp->data), &params, sizeof(params)))
+		return -EFAULT;
+
+	return 0;
 }
 
 static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
-- 
2.51.0