From: Oliver Upton <oupton@kernel.org>
Date: Mon, 24 Nov 2025 19:01:50 +0000 (-0800)
Subject: KVM: arm64: Handle endianness in read helper for emulated PTW
X-Git-Tag: v6.19-rc1~103^2~1^2^2~14
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fabf321cba4be0d0dcbb39e97c3deb572fec2f8d;p=thirdparty%2Flinux.git

KVM: arm64: Handle endianness in read helper for emulated PTW

Implementing FEAT_HAFDBS means adding another descriptor accessor that
needs to deal with the guest-configured endianness. Prepare by moving
the endianness handling into the read accessor and out of the main body
of the S1/S2 PTWs.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Link: https://msgid.link/20251124190158.177318-9-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
---

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index be26d5aa668c3..a295a37dd3b13 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -362,6 +362,24 @@ transfault:
 	return -EFAULT;
 }
 
+static int kvm_read_s1_desc(struct kvm_vcpu *vcpu, u64 pa, u64 *desc,
+			    struct s1_walk_info *wi)
+{
+	u64 val;
+	int r;
+
+	r = kvm_read_guest(vcpu->kvm, pa, &val, sizeof(val));
+	if (r)
+		return r;
+
+	if (wi->be)
+		*desc = be64_to_cpu((__force __be64)val);
+	else
+		*desc = le64_to_cpu((__force __le64)val);
+
+	return 0;
+}
+
 static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 		   struct s1_walk_result *wr, u64 va)
 {
@@ -414,17 +432,12 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 				return ret;
 		}
 
-		ret = kvm_read_guest(vcpu->kvm, ipa, &desc, sizeof(desc));
+		ret = kvm_read_s1_desc(vcpu, ipa, &desc, wi);
 		if (ret) {
 			fail_s1_walk(wr, ESR_ELx_FSC_SEA_TTW(level), false);
 			return ret;
 		}
 
-		if (wi->be)
-			desc = be64_to_cpu((__force __be64)desc);
-		else
-			desc = le64_to_cpu((__force __le64)desc);
-
 		/* Invalid descriptor */
 		if (!(desc & BIT(0)))
 			goto transfault;
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 94eff8307aada..75d26c0ba3e0c 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -197,9 +197,26 @@ static int check_output_size(struct s2_walk_info *wi, phys_addr_t output)
 	return 0;
 }
 
-static int read_guest_s2_desc(struct kvm_vcpu *vcpu, phys_addr_t pa, u64 *desc)
+static int read_guest_s2_desc(struct kvm_vcpu *vcpu, phys_addr_t pa, u64 *desc,
+			      struct s2_walk_info *wi)
 {
-	return kvm_read_guest(vcpu->kvm, pa, desc, sizeof(*desc));
+	u64 val;
+	int r;
+
+	r = kvm_read_guest(vcpu->kvm, pa, &val, sizeof(val));
+	if (r)
+		return r;
+
+	/*
+	 * Handle reversedescriptors if endianness differs between the
+	 * host and the guest hypervisor.
+	 */
+	if (wi->be)
+		*desc = be64_to_cpu((__force __be64)val);
+	else
+		*desc = le64_to_cpu((__force __le64)val);
+
+	return 0;
 }
 
 /*
@@ -260,19 +277,10 @@ static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, phys_addr_t ipa,
 			>> (addr_bottom - 3);
 
 		paddr = base_addr | index;
-		ret = read_guest_s2_desc(vcpu, paddr, &desc);
+		ret = read_guest_s2_desc(vcpu, paddr, &desc, wi);
 		if (ret < 0)
 			return ret;
 
-		/*
-		 * Handle reversedescriptors if endianness differs between the
-		 * host and the guest hypervisor.
-		 */
-		if (wi->be)
-			desc = be64_to_cpu((__force __be64)desc);
-		else
-			desc = le64_to_cpu((__force __le64)desc);
-
 		/* Check for valid descriptor at this point */
 		if (!(desc & 1) || ((desc & 3) == 1 && level == 3)) {
 			out->esr = compute_fsc(level, ESR_ELx_FSC_FAULT);