Laurent Vivier wrote:
> This patch is the kernel part of the "batch writes to MMIO" patch.
>
> When kernel has to send MMIO writes to userspace, it stores them
> in memory until it has to pass the hand to userspace for another
> reason. This avoids to have too many context switches on operations
> that can wait.
>
> WARNING: this breaks compatibility with old userspace part.
>
> Signed-off-by: Laurent Vivier <[EMAIL PROTECTED]>
> ---
> arch/x86/kvm/x86.c | 21 +++++++++++++++++++++
> include/asm-x86/kvm_host.h | 2 ++
> include/linux/kvm.h | 10 +++++++++-
> virt/kvm/kvm_main.c | 3 +++
> 4 files changed, 35 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0ce5563..3881056 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2942,8 +2942,21 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu,
> struct kvm_run *kvm_run)
> kvm_x86_ops->decache_regs(vcpu);
> }
>
> +batch:
> r = __vcpu_run(vcpu, kvm_run);
>
> + if (!r && vcpu->mmio_is_write &&
> + kvm_run->exit_reason == KVM_EXIT_MMIO &&
> + kvm_run->batch_count < KVM_MAX_BATCH) {
> + struct kvm_batch *batch = vcpu->arch.batch_data;
> + int i = kvm_run->batch_count++;
> +
> + batch[i].phys_addr = vcpu->mmio_phys_addr;
> + batch[i].len = vcpu->mmio_size;
> + memcpy(batch[i].data, vcpu->mmio_data, batch[i].len);
> +
> + goto batch;
> + }
>
I wonder if this is sufficient for dynticks enabled guests. __vcpu_run
could last a very long time.
Ignoring that for a moment, Avi's comment about having userspace tell
you which addresses to batch is an important one. MMIO writes may have
side effects and the next vcpu_run may rely on those side effects. For
instance, MMIO based IRQ acknowledgement.
You need a white list not only for performances purposes but also for
correctness.
Regards,
Anthony Liguori
-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference
Don't miss this year's exciting event. There's still time to save $100.
Use priority code J8TL2D2.
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone
_______________________________________________
kvm-devel mailing list
kvm-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/kvm-devel
