kvm: svm: Add kvm_fast_pio_in support

Update the I/O interception support to add the kvm_fast_pio_in function
to speed up the in instruction similar to the out instruction.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6f9c9ad13f88..ec59301f5192 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5615,6 +5615,49 @@ int kvm_fast_pio_out(struct kvm_vcpu *vcpu, int size, unsigned short port)
 }
 EXPORT_SYMBOL_GPL(kvm_fast_pio_out);
 
+static int complete_fast_pio_in(struct kvm_vcpu *vcpu)
+{
+	unsigned long val;
+
+	/* We should only ever be called with arch.pio.count equal to 1 */
+	BUG_ON(vcpu->arch.pio.count != 1);
+
+	/* For size less than 4 we merge, else we zero extend */
+	val = (vcpu->arch.pio.size < 4) ? kvm_register_read(vcpu, VCPU_REGS_RAX)
+					: 0;
+
+	/*
+	 * Since vcpu->arch.pio.count == 1 let emulator_pio_in_emulated perform
+	 * the copy and tracing
+	 */
+	emulator_pio_in_emulated(&vcpu->arch.emulate_ctxt, vcpu->arch.pio.size,
+				 vcpu->arch.pio.port, &val, 1);
+	kvm_register_write(vcpu, VCPU_REGS_RAX, val);
+
+	return 1;
+}
+
+int kvm_fast_pio_in(struct kvm_vcpu *vcpu, int size, unsigned short port)
+{
+	unsigned long val;
+	int ret;
+
+	/* For size less than 4 we merge, else we zero extend */
+	val = (size < 4) ? kvm_register_read(vcpu, VCPU_REGS_RAX) : 0;
+
+	ret = emulator_pio_in_emulated(&vcpu->arch.emulate_ctxt, size, port,
+				       &val, 1);
+	if (ret) {
+		kvm_register_write(vcpu, VCPU_REGS_RAX, val);
+		return ret;
+	}
+
+	vcpu->arch.complete_userspace_io = complete_fast_pio_in;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_fast_pio_in);
+
 static int kvmclock_cpu_down_prep(unsigned int cpu)
 {
 	__this_cpu_write(cpu_tsc_khz, 0);