Re: [PATCH v3 1/2] KVM: kvm-io: support cookies

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On Wed, Jul 03, 2013 at 03:50:38PM +0200, Cornelia Huck wrote:
> Add new functions kvm_io_bus_{read,write}_cookie() that allows users of
> the kvm io infrastructure to use a cookie value to speed up lookup of a
> device on an io bus.
> 
> kvm_io_bus_{read,write} now returns the index on the bus; existing callers
> have been fixed up to accept return codes > 0.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
> ---
>  arch/ia64/kvm/kvm-ia64.c   |   2 +-
>  arch/powerpc/kvm/powerpc.c |   4 +-
>  arch/x86/kvm/x86.c         |   6 +--
>  include/linux/kvm_host.h   |   4 ++
>  virt/kvm/kvm_main.c        | 102 ++++++++++++++++++++++++++++++++++++++-------
>  5 files changed, 97 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index 5b2dc0d..465ab54 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -250,7 +250,7 @@ mmio:
>  	else
>  		r = kvm_io_bus_write(vcpu->kvm, KVM_MMIO_BUS, p->addr,
>  				     p->size, &p->data);
> -	if (r)
> +	if (r < 0)
No need to change kvm_io_bus_(read|write) return value now. Just do
there:

  r = __kvm_io_bus_write(bus, &range, val);
  return  r >=0 ? 0 : r;

>  		printk(KERN_ERR"kvm: No iodevice found! addr:%lx\n", p->addr);
>  	p->state = STATE_IORESP_READY;
>  
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 6316ee3..26c44d0 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -649,7 +649,7 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  
>  	srcu_read_unlock(&vcpu->kvm->srcu, idx);
>  
> -	if (!ret) {
> +	if (ret >= 0) {
>  		kvmppc_complete_mmio_load(vcpu, run);
>  		vcpu->mmio_needed = 0;
>  		return EMULATE_DONE;
> @@ -711,7 +711,7 @@ int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  
>  	srcu_read_unlock(&vcpu->kvm->srcu, idx);
>  
> -	if (!ret) {
> +	if (ret >= 0) {
>  		vcpu->mmio_needed = 0;
>  		return EMULATE_DONE;
>  	}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7d71c0f..d58744b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3860,7 +3860,7 @@ static int vcpu_mmio_write(struct kvm_vcpu *vcpu, gpa_t addr, int len,
>  		n = min(len, 8);
>  		if (!(vcpu->arch.apic &&
>  		      !kvm_iodevice_write(&vcpu->arch.apic->dev, addr, n, v))
> -		    && kvm_io_bus_write(vcpu->kvm, KVM_MMIO_BUS, addr, n, v))
> +		    && (kvm_io_bus_write(vcpu->kvm, KVM_MMIO_BUS, addr, n, v) < 0))
>  			break;
>  		handled += n;
>  		addr += n;
> @@ -3880,7 +3880,7 @@ static int vcpu_mmio_read(struct kvm_vcpu *vcpu, gpa_t addr, int len, void *v)
>  		n = min(len, 8);
>  		if (!(vcpu->arch.apic &&
>  		      !kvm_iodevice_read(&vcpu->arch.apic->dev, addr, n, v))
> -		    && kvm_io_bus_read(vcpu->kvm, KVM_MMIO_BUS, addr, n, v))
> +		    && (kvm_io_bus_read(vcpu->kvm, KVM_MMIO_BUS, addr, n, v) < 0))
>  			break;
>  		trace_kvm_mmio(KVM_TRACE_MMIO_READ, n, addr, *(u64 *)v);
>  		handled += n;
> @@ -4361,7 +4361,7 @@ static int kernel_pio(struct kvm_vcpu *vcpu, void *pd)
>  		r = kvm_io_bus_write(vcpu->kvm, KVM_PIO_BUS,
>  				     vcpu->arch.pio.port, vcpu->arch.pio.size,
>  				     pd);
> -	return r;
> +	return (r >= 0) ? 0 : r;
>  }
>  
>  static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index e3aae6d..60e261c9 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -159,8 +159,12 @@ enum kvm_bus {
>  
>  int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  		     int len, const void *val);
> +int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> +			    int len, const void *val, long cookie);
>  int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len,
>  		    void *val);
> +int kvm_io_bus_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> +			   int len, void *val, long cookie);
>  int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  			    int len, struct kvm_io_device *dev);
>  int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1580dd4..eca3e00 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2863,11 +2863,30 @@ static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
>  	return off;
>  }
>  
> +static int __kvm_io_bus_write(struct kvm_io_bus *bus,
> +			      struct kvm_io_range *range, const void *val)
> +{
> +	int idx;
> +
> +	idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
> +	if (idx < 0)
> +		return -EOPNOTSUPP;
> +
> +	while (idx < bus->dev_count &&
> +		kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
> +		if (!kvm_iodevice_write(bus->range[idx].dev, range->addr,
> +					range->len, val))
> +			return idx;
> +		idx++;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
>  /* kvm_io_bus_write - called under kvm->slots_lock */
>  int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  		     int len, const void *val)
>  {
> -	int idx;
>  	struct kvm_io_bus *bus;
>  	struct kvm_io_range range;
>  
> @@ -2877,14 +2896,51 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  	};
>  
>  	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> -	idx = kvm_io_bus_get_first_dev(bus, addr, len);
> +	return __kvm_io_bus_write(bus, &range, val);
> +}
> +
> +/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
> +int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> +			    int len, const void *val, long cookie)
> +{
> +	struct kvm_io_bus *bus;
> +	struct kvm_io_range range;
> +
> +	range = (struct kvm_io_range) {
> +		.addr = addr,
> +		.len = len,
> +	};
> +
> +	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> +
> +	/* First try the device referenced by cookie. */
> +	if ((cookie >= 0) && (cookie < bus->dev_count) &&
> +	    (kvm_io_bus_sort_cmp(&range, &bus->range[cookie]) == 0))
> +		if (!kvm_iodevice_write(bus->range[cookie].dev, addr, len,
> +					val))
> +			return cookie;
> +
> +	/*
> +	 * cookie contained garbage; fall back to search and return the
> +	 * correct cookie value.
> +	 */
> +	return __kvm_io_bus_write(bus, &range, val);
> +}
> +
> +static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
> +			     void *val)
> +{
> +	int idx;
> +
> +	idx = kvm_io_bus_get_first_dev(bus, range->addr, range->len);
>  	if (idx < 0)
>  		return -EOPNOTSUPP;
>  
>  	while (idx < bus->dev_count &&
>  		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
> -		if (!kvm_iodevice_write(bus->range[idx].dev, addr, len, val))
> -			return 0;
> +		if (!kvm_iodevice_read(bus->range[idx].dev, range->addr,
> +				       range->len, val))
> +			return idx;
>  		idx++;
>  	}
>  
> @@ -2895,7 +2951,6 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  		    int len, void *val)
>  {
> -	int idx;
>  	struct kvm_io_bus *bus;
>  	struct kvm_io_range range;
>  
> @@ -2905,18 +2960,35 @@ int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  	};
>  
>  	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> -	idx = kvm_io_bus_get_first_dev(bus, addr, len);
> -	if (idx < 0)
> -		return -EOPNOTSUPP;
> +	return __kvm_io_bus_read(bus, &range, val);
> +}
>  
> -	while (idx < bus->dev_count &&
> -		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
> -		if (!kvm_iodevice_read(bus->range[idx].dev, addr, len, val))
> -			return 0;
> -		idx++;
> -	}
> +/* kvm_io_bus_read_cookie - called under kvm->slots_lock */
> +int kvm_io_bus_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> +			   int len, void *val, long cookie)
> +{
> +	struct kvm_io_bus *bus;
> +	struct kvm_io_range range;
>  
> -	return -EOPNOTSUPP;
> +	range = (struct kvm_io_range) {
> +		.addr = addr,
> +		.len = len,
> +	};
> +
> +	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> +
> +	/* First try the device referenced by cookie. */
> +	if ((cookie >= 0) && (cookie < bus->dev_count) &&
> +	    (kvm_io_bus_sort_cmp(&range, &bus->range[cookie]) == 0))
> +		if (!kvm_iodevice_read(bus->range[cookie].dev, addr, len,
> +				       val))
> +			return cookie;
> +
> +	/*
> +	 * cookie contained garbage; fall back to search and return the
> +	 * correct cookie value.
> +	 */
> +	return __kvm_io_bus_read(bus, &range, val);
>  }
>  
>  /* Caller must hold slots_lock. */
> -- 
> 1.8.2.2

--
			Gleb.
--
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