On Tue, Jun 12, 2012 at 03:01:27PM +0300, Gleb Natapov wrote:
> "rep ins" emulation is going through emulator now. This is slow because
> emulator knows how to write back only one datum at a time. This patch
> provides fast path for the instruction in certain conditions. The
> conditions are: DF flag is not set, destination memory is RAM and single
> datum does not cross page boundary. If fast path code fails it falls
> back to emulation.
>
> Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 6 ++
> arch/x86/kvm/svm.c | 20 +++++--
> arch/x86/kvm/vmx.c | 25 +++++--
> arch/x86/kvm/x86.c | 133 ++++++++++++++++++++++++++++++++++++--
> 4 files changed, 165 insertions(+), 19 deletions(-)
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 7a41878..f3e7bb3 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1887,21 +1887,31 @@ static int io_interception(struct vcpu_svm *svm)
> {
> struct kvm_vcpu *vcpu = &svm->vcpu;
> u32 io_info = svm->vmcb->control.exit_info_1; /* address size bug? */
> - int size, in, string;
> + int size, in, string, rep;
> unsigned port;
>
> ++svm->vcpu.stat.io_exits;
> string = (io_info & SVM_IOIO_STR_MASK) != 0;
> + rep = (io_info & SVM_IOIO_REP_MASK) != 0;
> in = (io_info & SVM_IOIO_TYPE_MASK) != 0;
> - if (string || in)
> - return emulate_instruction(vcpu, 0) == EMULATE_DONE;
>
> port = io_info >> 16;
> size = (io_info & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT;
> svm->next_rip = svm->vmcb->control.exit_info_2;
> - skip_emulated_instruction(&svm->vcpu);
>
> - return kvm_fast_pio_out(vcpu, size, port);
> + if (!string && !in) {
> + skip_emulated_instruction(&svm->vcpu);
> + return kvm_fast_pio_out(vcpu, size, port);
> + } else if (string && in && rep) {
Is there a reason to restrict optimization to rep ? That is,
it should be easy to extend to normal in?
> + kvm_x86_ops->skip_emulated_instruction(vcpu);
> + return EMULATE_DONE;
> + }
> + if (kvm_get_rflags(vcpu) & X86_EFLAGS_DF)
> + return EMULATE_FAIL;
> + if (ad_bytes_idx > 2)
> + return EMULATE_FAIL;
> +
> + ad_bytes = (u8[]){2, 4, 8}[ad_bytes_idx];
> +
> + rdi = kvm_address_mask(ad_bytes, rdi);
> +
> + count = (PAGE_SIZE - offset_in_page(rdi))/size;
> +
> + if (count == 0) /* 'in' crosses page boundry */
> + return EMULATE_FAIL;
> +
> + count = min(count, kvm_address_mask(ad_bytes, rcx));
> +
> + r = kvm_linearize_address(vcpu, get_emulation_mode(vcpu),
> + rdi, VCPU_SREG_ES, count, true, false, ad_bytes,
> + &linear_addr);
kvm_linearize_address expects size parameter in bytes?
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