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

Marcelo Tosatti
2015-03-13T00:47:09Z

On Mon, Mar 02, 2015 at 03:02:02PM -0600, Joel Schopp wrote:
> 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));

Weird.

> + 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;

Please zero initialize val.
Please check sanity of size.