[PATCH v2 2/3] kvm: svm: Add kvm_fast_pio_in support

Brijesh Singh
2016-11-23T17:35:07Z

From: Tom Lendacky <thomas.lendacky@amd.com>

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>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm.c | 5 +++--
arch/x86/kvm/x86.c | 43 +++++++++++++++++++++++++++++++++++++++
3 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index da07e17..77cb3f9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1133,6 +1133,7 @@ int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
struct x86_emulate_ctxt;

int kvm_fast_pio_out(struct kvm_vcpu *vcpu, int size, unsigned short port);
+int kvm_fast_pio_in(struct kvm_vcpu *vcpu, int size, unsigned short port);
void kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
int kvm_emulate_halt(struct kvm_vcpu *vcpu);
int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4e462bb..5e64e656 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2270,7 +2270,7 @@ static int io_interception(struct vcpu_svm *svm)
++svm->vcpu.stat.io_exits;
string = (io_info & SVM_IOIO_STR_MASK) != 0;
in = (io_info & SVM_IOIO_TYPE_MASK) != 0;
- if (string || in)
+ if (string)
return emulate_instruction(vcpu, 0) == EMULATE_DONE;

port = io_info >> 16;
@@ -2278,7 +2278,8 @@ static int io_interception(struct vcpu_svm *svm)
svm->next_rip = svm->vmcb->control.exit_info_2;
skip_emulated_instruction(&svm->vcpu);

- return kvm_fast_pio_out(vcpu, size, port);
+ return in ? kvm_fast_pio_in(vcpu, size, port)
+ : kvm_fast_pio_out(vcpu, size, port);
}

static int nmi_interception(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 04c5d96..c30f62dc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5638,6 +5638,49 @@ 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);