[PATCH 1/2] KVM: arm64: Fix sign-extension of MMIO loads

[Fuad Tabba <fuad.tabba@linux.dev>]

A sign-extending load from MMIO (LDRSB, LDRSH, LDRSW) delivers a
zero-extended value: in kvm_handle_mmio_return(), vcpu_data_host_to_guest()
masks the data to the access width after sign-extension, stripping the
sign bits.

Move vcpu_data_host_to_guest() ahead of sign-extension so the width mask
runs first. trace_kvm_mmio() moves with it and keeps reporting the raw
access-width data.

Fixes: b30070862edbd ("ARM64: KVM: MMIO support BE host running LE code")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/kvm/mmio.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c
index e2285ed8c91de..d1c3a352d5a22 100644
--- a/arch/arm64/kvm/mmio.c
+++ b/arch/arm64/kvm/mmio.c
@@ -126,6 +126,10 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
 		len = kvm_vcpu_dabt_get_as(vcpu);
 		data = kvm_mmio_read_buf(run->mmio.data, len);
 
+		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
+			       &data);
+		data = vcpu_data_host_to_guest(vcpu, data, len);
+
 		if (kvm_vcpu_dabt_issext(vcpu) &&
 		    len < sizeof(unsigned long)) {
 			mask = 1U << ((len * 8) - 1);
@@ -135,9 +139,6 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
 		if (!kvm_vcpu_dabt_issf(vcpu))
 			data = data & 0xffffffff;
 
-		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
-			       &data);
-		data = vcpu_data_host_to_guest(vcpu, data, len);
 		vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);
 	}
 
-- 
2.39.5