[PATCH v4 0/2] KVM: ioeventfd cookies

[PATCH v4 0/2] KVM: ioeventfd cookies

[Cornelia Huck]

Hi,

fourth version of this patch set.

Changes:
- make the cookie-less read/write function return 0 again on success and
  drop the changes at the callsites

Cornelia Huck (2):
  KVM: kvm-io: support cookies
  KVM: s390: use cookies for ioeventfd

 arch/s390/kvm/diag.c     |  15 +++++--
 include/linux/kvm_host.h |   4 ++
 virt/kvm/kvm_main.c      | 106 ++++++++++++++++++++++++++++++++++++++++-------
 3 files changed, 107 insertions(+), 18 deletions(-)

-- 
1.8.2.2

[PATCH v4 1/2] KVM: kvm-io: support cookies

[Cornelia Huck]

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.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
 include/linux/kvm_host.h |   4 ++
 virt/kvm/kvm_main.c      | 106 ++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 95 insertions(+), 15 deletions(-)

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..c7f5355 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2863,11 +2863,48 @@ 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;
+	int r;
+
+	range = (struct kvm_io_range) {
+		.addr = addr,
+		.len = len,
+	};
+
+	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+	r = __kvm_io_bus_write(bus, &range, val);
+	return r < 0 ? r : 0;
+}
+
+/* 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;
 
@@ -2877,14 +2914,35 @@ 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);
+
+	/* 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++;
 	}
 
@@ -2895,9 +2953,9 @@ 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;
+	int r;
 
 	range = (struct kvm_io_range) {
 		.addr = addr,
@@ -2905,18 +2963,36 @@ 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;
+	r = __kvm_io_bus_read(bus, &range, val);
+	return r < 0 ? r : 0;
+}
 
-	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

Re: [PATCH v4 1/2] KVM: kvm-io: support cookies

[Gleb Natapov]

On Wed, Jul 03, 2013 at 04:30:53PM +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.
> 
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Looks good to me now.

> ---
>  include/linux/kvm_host.h |   4 ++
>  virt/kvm/kvm_main.c      | 106 ++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 95 insertions(+), 15 deletions(-)
> 
> 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..c7f5355 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2863,11 +2863,48 @@ 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;
> +	int r;
> +
> +	range = (struct kvm_io_range) {
> +		.addr = addr,
> +		.len = len,
> +	};
> +
> +	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
> +	r = __kvm_io_bus_write(bus, &range, val);
> +	return r < 0 ? r : 0;
> +}
> +
> +/* 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;
>  
> @@ -2877,14 +2914,35 @@ 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);
> +
> +	/* 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++;
>  	}
>  
> @@ -2895,9 +2953,9 @@ 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;
> +	int r;
>  
>  	range = (struct kvm_io_range) {
>  		.addr = addr,
> @@ -2905,18 +2963,36 @@ 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;
> +	r = __kvm_io_bus_read(bus, &range, val);
> +	return r < 0 ? r : 0;
> +}
>  
> -	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.

[PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Cornelia Huck]

Make use of cookies for the virtio ccw notification hypercall to speed up
lookup of devices on the io bus.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
 arch/s390/kvm/diag.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 3074475..e88c76e 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -119,11 +119,20 @@ static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
 	 * The layout is as follows:
 	 * - gpr 2 contains the subchannel id (passed as addr)
 	 * - gpr 3 contains the virtqueue index (passed as datamatch)
+	 * - gpr 4 contains the index on the bus (optionally)
 	 */
-	ret = kvm_io_bus_write(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
-				vcpu->run->s.regs.gprs[2],
-				8, &vcpu->run->s.regs.gprs[3]);
+	ret = kvm_io_bus_write_cookie(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
+				      vcpu->run->s.regs.gprs[2],
+				      8, &vcpu->run->s.regs.gprs[3],
+				      vcpu->run->s.regs.gprs[4]);
 	srcu_read_unlock(&vcpu->kvm->srcu, idx);
+
+	/*
+	 * Return cookie in gpr 2, but don't overwrite the register if the
+	 * diagnose will be handled by userspace.
+	 */
+	if (ret != -EOPNOTSUPP)
+		vcpu->run->s.regs.gprs[2] = ret;
 	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
 	return ret < 0 ? ret : 0;
 }
-- 
1.8.2.2

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Paolo Bonzini]

Il 03/07/2013 16:30, Cornelia Huck ha scritto:
> +	/*
> +	 * Return cookie in gpr 2, but don't overwrite the register if the
> +	 * diagnose will be handled by userspace.
> +	 */
> +	if (ret != -EOPNOTSUPP)
> +		vcpu->run->s.regs.gprs[2] = ret;

I think this should now be "if (ret >= 0)".

>  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */

The comment is now obsolete.

>  	return ret < 0 ? ret : 0;

Otherwise looks good, thanks!

Paolo

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Cornelia Huck]

On Wed, 03 Jul 2013 17:30:40 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 03/07/2013 16:30, Cornelia Huck ha scritto:
> > +	/*
> > +	 * Return cookie in gpr 2, but don't overwrite the register if the
> > +	 * diagnose will be handled by userspace.
> > +	 */
> > +	if (ret != -EOPNOTSUPP)
> > +		vcpu->run->s.regs.gprs[2] = ret;
> 
> I think this should now be "if (ret >= 0)".

Hm, we don't want to kill gpr 2's old contents if userspace will do
something, which means -EOPNOTSUPP.

> 
> >  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
> 
> The comment is now obsolete.

s/kvm_io_bus_write/kvm_io_bus_write_cookie/ ? Otherwise, this is still
true.

> 
> >  	return ret < 0 ? ret : 0;
> 
> Otherwise looks good, thanks!
> 
> Paolo
> 

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Paolo Bonzini]

Il 03/07/2013 18:33, Cornelia Huck ha scritto:
> On Wed, 03 Jul 2013 17:30:40 +0200
> Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>> Il 03/07/2013 16:30, Cornelia Huck ha scritto:
>>> +	/*
>>> +	 * Return cookie in gpr 2, but don't overwrite the register if the
>>> +	 * diagnose will be handled by userspace.
>>> +	 */
>>> +	if (ret != -EOPNOTSUPP)
>>> +		vcpu->run->s.regs.gprs[2] = ret;
>>
>> I think this should now be "if (ret >= 0)".
> 
> Hm, we don't want to kill gpr 2's old contents if userspace will do
> something, which means -EOPNOTSUPP.

In the end kvm_io_bus_write_cookie only returns -EOPNOTSUPP if there is
an error, so it works.  But if this were to change, the code would
break.  That's why I suggested testing "ret >= 0" rather than "ret !=
-EOPNOTSUPP".  But in the end it is the same.

>>
>>>  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
>>
>> The comment is now obsolete.
> 
> s/kvm_io_bus_write/kvm_io_bus_write_cookie/ ? Otherwise, this is still
> true.

True but somewhat misplaced, it is basically saying the same thing as
the "Return cookie in gpr 2" comment just above.

Anyhow, these are very small details.  I changed kvm_io_bus_write to
kvm_io_bus_write_cookie in the comment and applied the patches to kvm-queue.

Paolo

>>
>>>  	return ret < 0 ? ret : 0;
>>
>> Otherwise looks good, thanks!
>>
>> Paolo
>>
> 
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> 

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Gleb Natapov]

On Thu, Jul 04, 2013 at 08:54:32AM +0200, Paolo Bonzini wrote:
> Il 03/07/2013 18:33, Cornelia Huck ha scritto:
> > On Wed, 03 Jul 2013 17:30:40 +0200
> > Paolo Bonzini <pbonzini@redhat.com> wrote:
> > 
> >> Il 03/07/2013 16:30, Cornelia Huck ha scritto:
> >>> +	/*
> >>> +	 * Return cookie in gpr 2, but don't overwrite the register if the
> >>> +	 * diagnose will be handled by userspace.
> >>> +	 */
> >>> +	if (ret != -EOPNOTSUPP)
> >>> +		vcpu->run->s.regs.gprs[2] = ret;
> >>
> >> I think this should now be "if (ret >= 0)".
> > 
> > Hm, we don't want to kill gpr 2's old contents if userspace will do
> > something, which means -EOPNOTSUPP.
> 
> In the end kvm_io_bus_write_cookie only returns -EOPNOTSUPP if there is
> an error, so it works.  But if this were to change, the code would
> break.  That's why I suggested testing "ret >= 0" rather than "ret !=
> -EOPNOTSUPP".  But in the end it is the same.
> 
> >>
> >>>  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
> >>
> >> The comment is now obsolete.
> > 
> > s/kvm_io_bus_write/kvm_io_bus_write_cookie/ ? Otherwise, this is still
> > true.
> 
> True but somewhat misplaced, it is basically saying the same thing as
> the "Return cookie in gpr 2" comment just above.
> 
> Anyhow, these are very small details.  I changed kvm_io_bus_write to
> kvm_io_bus_write_cookie in the comment and applied the patches to kvm-queue.
> 
1/2 broke x86. QEMU prints "Invalid read from memory region kvm-pic" and
guest hangs. Looks like IO is forwarded to userspace instead of in kernel device
for some reason. Un-applying for now.

--
			Gleb.

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Gleb Natapov]

On Sun, Jul 14, 2013 at 12:25:16PM +0300, Gleb Natapov wrote:
> On Thu, Jul 04, 2013 at 08:54:32AM +0200, Paolo Bonzini wrote:
> > Il 03/07/2013 18:33, Cornelia Huck ha scritto:
> > > On Wed, 03 Jul 2013 17:30:40 +0200
> > > Paolo Bonzini <pbonzini@redhat.com> wrote:
> > > 
> > >> Il 03/07/2013 16:30, Cornelia Huck ha scritto:
> > >>> +	/*
> > >>> +	 * Return cookie in gpr 2, but don't overwrite the register if the
> > >>> +	 * diagnose will be handled by userspace.
> > >>> +	 */
> > >>> +	if (ret != -EOPNOTSUPP)
> > >>> +		vcpu->run->s.regs.gprs[2] = ret;
> > >>
> > >> I think this should now be "if (ret >= 0)".
> > > 
> > > Hm, we don't want to kill gpr 2's old contents if userspace will do
> > > something, which means -EOPNOTSUPP.
> > 
> > In the end kvm_io_bus_write_cookie only returns -EOPNOTSUPP if there is
> > an error, so it works.  But if this were to change, the code would
> > break.  That's why I suggested testing "ret >= 0" rather than "ret !=
> > -EOPNOTSUPP".  But in the end it is the same.
> > 
> > >>
> > >>>  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
> > >>
> > >> The comment is now obsolete.
> > > 
> > > s/kvm_io_bus_write/kvm_io_bus_write_cookie/ ? Otherwise, this is still
> > > true.
> > 
> > True but somewhat misplaced, it is basically saying the same thing as
> > the "Return cookie in gpr 2" comment just above.
> > 
> > Anyhow, these are very small details.  I changed kvm_io_bus_write to
> > kvm_io_bus_write_cookie in the comment and applied the patches to kvm-queue.
> > 
> 1/2 broke x86. QEMU prints "Invalid read from memory region kvm-pic" and
> guest hangs. Looks like IO is forwarded to userspace instead of in kernel device
> for some reason. Un-applying for now.
> 
OK, stupid typo. Will amend the commit instead of dropping.


diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6cde6fa..a86735d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2942,7 +2942,7 @@ static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
 		return -EOPNOTSUPP;
 
 	while (idx < bus->dev_count &&
-		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
+		kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
 		if (!kvm_iodevice_read(bus->range[idx].dev, range->addr,
 				       range->len, val))
 			return idx;
--
			Gleb.

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Cornelia Huck]

On Sun, 14 Jul 2013 13:19:59 +0300
Gleb Natapov <gleb@redhat.com> wrote:

> On Sun, Jul 14, 2013 at 12:25:16PM +0300, Gleb Natapov wrote:

> > 1/2 broke x86. QEMU prints "Invalid read from memory region kvm-pic" and
> > guest hangs. Looks like IO is forwarded to userspace instead of in kernel device
> > for some reason. Un-applying for now.
> > 
> OK, stupid typo. Will amend the commit instead of dropping.
> 

Thanks for fixing.

> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 6cde6fa..a86735d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2942,7 +2942,7 @@ static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
>  		return -EOPNOTSUPP;
> 
>  	while (idx < bus->dev_count &&
> -		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
> +		kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
>  		if (!kvm_iodevice_read(bus->range[idx].dev, range->addr,
>  				       range->len, val))
>  			return idx;
> --
> 			Gleb.
> 

Re: [PATCH v4 2/2] KVM: s390: use cookies for ioeventfd

[Paolo Bonzini]

Il 14/07/2013 12:19, Gleb Natapov ha scritto:
> On Sun, Jul 14, 2013 at 12:25:16PM +0300, Gleb Natapov wrote:
>> On Thu, Jul 04, 2013 at 08:54:32AM +0200, Paolo Bonzini wrote:
>>> Il 03/07/2013 18:33, Cornelia Huck ha scritto:
>>>> On Wed, 03 Jul 2013 17:30:40 +0200
>>>> Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>>
>>>>> Il 03/07/2013 16:30, Cornelia Huck ha scritto:
>>>>>> +	/*
>>>>>> +	 * Return cookie in gpr 2, but don't overwrite the register if the
>>>>>> +	 * diagnose will be handled by userspace.
>>>>>> +	 */
>>>>>> +	if (ret != -EOPNOTSUPP)
>>>>>> +		vcpu->run->s.regs.gprs[2] = ret;
>>>>>
>>>>> I think this should now be "if (ret >= 0)".
>>>>
>>>> Hm, we don't want to kill gpr 2's old contents if userspace will do
>>>> something, which means -EOPNOTSUPP.
>>>
>>> In the end kvm_io_bus_write_cookie only returns -EOPNOTSUPP if there is
>>> an error, so it works.  But if this were to change, the code would
>>> break.  That's why I suggested testing "ret >= 0" rather than "ret !=
>>> -EOPNOTSUPP".  But in the end it is the same.
>>>
>>>>>
>>>>>>  	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
>>>>>
>>>>> The comment is now obsolete.
>>>>
>>>> s/kvm_io_bus_write/kvm_io_bus_write_cookie/ ? Otherwise, this is still
>>>> true.
>>>
>>> True but somewhat misplaced, it is basically saying the same thing as
>>> the "Return cookie in gpr 2" comment just above.
>>>
>>> Anyhow, these are very small details.  I changed kvm_io_bus_write to
>>> kvm_io_bus_write_cookie in the comment and applied the patches to kvm-queue.
>>>
>> 1/2 broke x86. QEMU prints "Invalid read from memory region kvm-pic" and
>> guest hangs. Looks like IO is forwarded to userspace instead of in kernel device
>> for some reason. Un-applying for now.
>>
> OK, stupid typo. Will amend the commit instead of dropping.
> 
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 6cde6fa..a86735d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2942,7 +2942,7 @@ static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
>  		return -EOPNOTSUPP;
>  
>  	while (idx < bus->dev_count &&
> -		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
> +		kvm_io_bus_sort_cmp(range, &bus->range[idx]) == 0) {
>  		if (!kvm_iodevice_read(bus->range[idx].dev, range->addr,
>  				       range->len, val))
>  			return idx;
> --
> 			Gleb.
> 

We can introduce an

int __kvm_io_bus_sort_cmp(const struct kvm_io_range *p1, const struct kvm_io_range *p2)

function so that this kind of typo doesn't happen again in the future.

I'll post a patch later.

Paolo