2015-03-02 10:40-0600, Joel Schopp:
> From: David Kaplan <david.kap...@amd.com>
>
> We can make the in instruction go faster the same way the out instruction is
> already.
>
> Changes from v1
> * Added kvm_fast_pio_in() implementation that was left out of v1
>
> Signed-off-by: David Kaplan <david.kap...@amd.com>
> [extracted from larger unlrelated patch, forward ported, tested]
> Signed-off-by: Joel Schopp <joel.sch...@amd.com>
> ---
> 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)
(I guess that most accesses are covered now, so we don't need to make
REP case a bit faster ...)
> 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);
(kvm_fast_pio() comes to mind.)
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bd7a70b..089247c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5463,6 +5463,39 @@ 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)
> +{
> + u32 new_rax = kvm_register_read(vcpu, VCPU_REGS_RAX);
u64.
> +
> + if (!vcpu->arch.pio.count)
> + return 0;
> + if (vcpu->arch.pio.count * vcpu->arch.pio.size > 8)
> + return 0;
sizeof(new_rax). (safer and easier to understand)
Both should never happen in KVM code, BUG_ON().
> +
> + memcpy(&new_rax, vcpu->arch.pio_data,
> + vcpu->arch.pio.count * vcpu->arch.pio.size);
Use emulator_pio_in_emulated() here, for code sharing.
(We want to trace the read here too; it could be better to split
the path from emulator_pio_in_emulated() first.)
> + 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);
> + vcpu->arch.pio.count = 0;
(emulator_pio_in_emulated() sets count to zero if it returns true.)
> + } 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);
>
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