Re: [PATCHv2 1/5] Provide userspace IO exit completion callback.

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, Jun 12, 2012 at 03:01:23PM +0300, Gleb Natapov wrote:
> Current code assumes that IO exit was due to instruction emulation
> and handles execution back to emulator directly. This patch adds new
> userspace IO exit completion callback that can be set by any other code
> that caused IO exit to userspace.
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |    1 +
>  arch/x86/kvm/x86.c              |   92 +++++++++++++++++++++++----------------
>  2 files changed, 56 insertions(+), 37 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index db7c1f2..1a1bba6 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -406,6 +406,7 @@ struct kvm_vcpu_arch {
>  	struct x86_emulate_ctxt emulate_ctxt;
>  	bool emulate_regs_need_sync_to_vcpu;
>  	bool emulate_regs_need_sync_from_vcpu;
> +	int (*complete_userspace_io)(struct kvm_vcpu *vcpu);
>  
>  	gpa_t time;
>  	struct pvclock_vcpu_time_info hv_clock;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a01a424..6fa0e21 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4547,6 +4547,9 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
>  	return true;
>  }
>  
> +static int complete_emulated_mmio(struct kvm_vcpu *vcpu);
> +static int complete_emulated_pio(struct kvm_vcpu *vcpu);
> +
>  int x86_emulate_instruction(struct kvm_vcpu *vcpu,
>  			    unsigned long cr2,
>  			    int emulation_type,
> @@ -4617,13 +4620,16 @@ restart:
>  	} else if (vcpu->arch.pio.count) {
>  		if (!vcpu->arch.pio.in)
>  			vcpu->arch.pio.count = 0;
> -		else
> +		else {
>  			writeback = false;
> +			vcpu->arch.complete_userspace_io = complete_emulated_pio;
> +		}
>  		r = EMULATE_DO_MMIO;
>  	} else if (vcpu->mmio_needed) {
>  		if (!vcpu->mmio_is_write)
>  			writeback = false;
>  		r = EMULATE_DO_MMIO;
> +		vcpu->arch.complete_userspace_io = complete_emulated_mmio;
>  	} else if (r == EMULATION_RESTART)
>  		goto restart;
>  	else
> @@ -5474,6 +5480,24 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>  	return r;
>  }
>  
> +static inline int complete_emulated_io(struct kvm_vcpu *vcpu)
> +{
> +	int r;
> +	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +	r = emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
> +	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> +	if (r != EMULATE_DONE)
> +		return 0;
> +	return 1;
> +}
> +
> +static int complete_emulated_pio(struct kvm_vcpu *vcpu)
> +{
> +	BUG_ON(!vcpu->arch.pio.count);
> +
> +	return complete_emulated_io(vcpu);
> +}
> +
>  /*
>   * Implements the following, as a state machine:
>   *
> @@ -5490,47 +5514,37 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>   *      copy data
>   *      exit
>   */
> -static int complete_mmio(struct kvm_vcpu *vcpu)
> +static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_run *run = vcpu->run;
>  	struct kvm_mmio_fragment *frag;
> -	int r;
>  
> -	if (!(vcpu->arch.pio.count || vcpu->mmio_needed))
> -		return 1;
> +	BUG_ON(!vcpu->mmio_needed);
>  
> -	if (vcpu->mmio_needed) {
> -		/* Complete previous fragment */
> -		frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment++];
> -		if (!vcpu->mmio_is_write)
> -			memcpy(frag->data, run->mmio.data, frag->len);
> -		if (vcpu->mmio_cur_fragment == vcpu->mmio_nr_fragments) {
> -			vcpu->mmio_needed = 0;
> -			if (vcpu->mmio_is_write)
> -				return 1;
> -			vcpu->mmio_read_completed = 1;
> -			goto done;
> -		}
> -		/* Initiate next fragment */
> -		++frag;
> -		run->exit_reason = KVM_EXIT_MMIO;
> -		run->mmio.phys_addr = frag->gpa;
> +	/* Complete previous fragment */
> +	frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment++];
> +	if (!vcpu->mmio_is_write)
> +		memcpy(frag->data, run->mmio.data, frag->len);
> +	if (vcpu->mmio_cur_fragment == vcpu->mmio_nr_fragments) {
> +		vcpu->mmio_needed = 0;
>  		if (vcpu->mmio_is_write)
> -			memcpy(run->mmio.data, frag->data, frag->len);
> -		run->mmio.len = frag->len;
> -		run->mmio.is_write = vcpu->mmio_is_write;
> -		return 0;
> -
> -	}
> -done:
> -	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> -	r = emulate_instruction(vcpu, EMULTYPE_NO_DECODE);
> -	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> -	if (r != EMULATE_DONE)
> -		return 0;
> -	return 1;
> +			return 1;
> +		vcpu->mmio_read_completed = 1;
> +		return complete_emulated_io(vcpu);
> +	}
> +	/* Initiate next fragment */
> +	++frag;
> +	run->exit_reason = KVM_EXIT_MMIO;
> +	run->mmio.phys_addr = frag->gpa;
> +	if (vcpu->mmio_is_write)
> +		memcpy(run->mmio.data, frag->data, frag->len);
> +	run->mmio.len = frag->len;
> +	run->mmio.is_write = vcpu->mmio_is_write;
> +	vcpu->arch.complete_userspace_io = complete_emulated_mmio;
> +	return 0;
>  }
>  
> +
>  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  {
>  	int r;
> @@ -5557,9 +5571,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  		}
>  	}
>  
> -	r = complete_mmio(vcpu);
> -	if (r <= 0)
> -		goto out;
> +	if (unlikely(vcpu->arch.complete_userspace_io)) {
> +		int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
> +		vcpu->arch.complete_userspace_io = NULL;
> +		r = cui(vcpu);
> +		if (r <= 0)

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