[PATCH v3] x86: svm: use kvm_fast_pio_in()

Joel Schopp
2015-03-02T20:58:12Z

From: David Kaplan <David.Kaplan@amd.com>

We can make the in instruction go faster the same way the out instruction is
already.

Changes from v2[Joel]:
* changed rax from u32 to unsigned long
* changed a couple return 0 to BUG_ON()
* changed 8 to sizeof(new_rax)
* added trace hook
* removed redundant clearing of count
Changes from v1[Joel]
* Added kvm_fast_pio_in() implementation that was left out of v1

Signed-off-by: David Kaplan <David.Kaplan@amd.com>
[extracted from larger unlrelated patch, forward ported, addressed reviews, tested]
Signed-off-by: Joel Schopp <joel.schopp@amd.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm.c | 4 +++-
arch/x86/kvm/x86.c | 30 ++++++++++++++++++++++++++++++
3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a236e39..b976824 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -931,6 +931,7 @@ 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_emulate_wbinvd(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d319e0c..f8c906b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1899,7 +1899,7 @@ 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;
@@ -1907,6 +1907,8 @@ static int io_interception(struct vcpu_svm *svm)
svm->next_rip = svm->vmcb->control.exit_info_2;
skip_emulated_instruction(&svm->vcpu);

+ if (in)
+ return kvm_fast_pio_in(vcpu, size, port);
return kvm_fast_pio_out(vcpu, size, port);
}

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bd7a70b..d05efaf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5463,6 +5463,36 @@ 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(struct kvm_vcpu *vcpu)
+{
+ unsigned long new_rax = kvm_register_read(vcpu, VCPU_REGS_RAX);
+
+ BUG_ON(!vcpu->arch.pio.count);
+ BUG_ON(vcpu->arch.pio.count * vcpu->arch.pio.size > sizeof(new_rax));
+
+ memcpy(&new_rax, vcpu, sizeof(new_rax));
+ trace_kvm_pio(KVM_PIO_IN, vcpu->arch.pio.port, vcpu->arch.pio.size,
+ vcpu->arch.pio.count, vcpu->arch.pio_data);
+ kvm_register_write(vcpu, VCPU_REGS_RAX, new_rax);
+ vcpu->arch.pio.count = 0;
+ return 1;
+}
+
+int kvm_fast_pio_in(struct kvm_vcpu *vcpu, int size, unsigned short port)
+{
+ unsigned long val;
+ int ret = emulator_pio_in_emulated(&vcpu->arch.emulate_ctxt, size,
+ port, &val, 1);
+
+ if (ret)
+ kvm_register_write(vcpu, VCPU_REGS_RAX, val);
+ else
+ vcpu->arch.complete_userspace_io = complete_fast_pio;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kvm_fast_pio_in);
+
static void tsc_bad(void *info)
{
__this_cpu_write(cpu_tsc_khz, 0);