Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 01:58:43PM +0100, Geert Uytterhoeven wrote:
> On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin wrote:
> > On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
> >> On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin
> >> wrote:
> >> > virtio 1.0 makes all memory structures LE, so
> >> > we need APIs to conditionally do a byteswap on BE
> >> > architectures.
> >> >
> >> > To make it easier to check code statically,
> >> > add virtio specific types for multi-byte integers
> >> > in memory.
> >> >
> >> > Add low level wrappers that do a byteswap conditionally, these will be
> >> > useful e.g. for vhost. Add high level wrappers that
> >> > query device endian-ness and act accordingly.
> >>
> >> > diff --git a/include/linux/virtio_byteorder.h
> >> > b/include/linux/virtio_byteorder.h
> >> > new file mode 100644
> >> > index 000..824ed0b
> >> > --- /dev/null
> >> > +++ b/include/linux/virtio_byteorder.h
> >>
> >> > +static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
> >> > +{
> >> > + if (little_endian)
> >> > + return le16_to_cpu((__force __le16)val);
> >> > + else
> >> > + return (__force u16)val;
> >> > +}
> >>
> >> What's wrong with just using le16-to_cpu() ...
> >
> > le16-to_cpu() is simply wrong: virtio needs to be
> > LE or native endian, depending on whether it's running
> > in 0.9 or 1.0 mode.
>
> IC, that was not clear from the description for this patch.
> I thought it was dependent on BE architectures.
>
> Nevertheless, any chance you can get rid of the "conditional"?
I don't see how - this is fundamental to any virtio device
that wants to support both 0.9 and 1.0 from the same
codebase.
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
> ge...@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like
> that.
> -- Linus Torvalds
--
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Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin wrote:
> On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
>> On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin wrote:
>> > virtio 1.0 makes all memory structures LE, so
>> > we need APIs to conditionally do a byteswap on BE
>> > architectures.
>> >
>> > To make it easier to check code statically,
>> > add virtio specific types for multi-byte integers
>> > in memory.
>> >
>> > Add low level wrappers that do a byteswap conditionally, these will be
>> > useful e.g. for vhost. Add high level wrappers that
>> > query device endian-ness and act accordingly.
>>
>> > diff --git a/include/linux/virtio_byteorder.h
>> > b/include/linux/virtio_byteorder.h
>> > new file mode 100644
>> > index 000..824ed0b
>> > --- /dev/null
>> > +++ b/include/linux/virtio_byteorder.h
>>
>> > +static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
>> > +{
>> > + if (little_endian)
>> > + return le16_to_cpu((__force __le16)val);
>> > + else
>> > + return (__force u16)val;
>> > +}
>>
>> What's wrong with just using le16-to_cpu() ...
>
> le16-to_cpu() is simply wrong: virtio needs to be
> LE or native endian, depending on whether it's running
> in 0.9 or 1.0 mode.
IC, that was not clear from the description for this patch.
I thought it was dependent on BE architectures.
Nevertheless, any chance you can get rid of the "conditional"?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
> On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin wrote:
> > virtio 1.0 makes all memory structures LE, so
> > we need APIs to conditionally do a byteswap on BE
> > architectures.
> >
> > To make it easier to check code statically,
> > add virtio specific types for multi-byte integers
> > in memory.
> >
> > Add low level wrappers that do a byteswap conditionally, these will be
> > useful e.g. for vhost. Add high level wrappers that
> > query device endian-ness and act accordingly.
>
> > diff --git a/include/linux/virtio_byteorder.h
> > b/include/linux/virtio_byteorder.h
> > new file mode 100644
> > index 000..824ed0b
> > --- /dev/null
> > +++ b/include/linux/virtio_byteorder.h
>
> > +static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
> > +{
> > + if (little_endian)
> > + return le16_to_cpu((__force __le16)val);
> > + else
> > + return (__force u16)val;
> > +}
>
> What's wrong with just using le16-to_cpu() ...
le16-to_cpu() is simply wrong: virtio needs to be
LE or native endian, depending on whether it's running
in 0.9 or 1.0 mode.
> > --- a/include/uapi/linux/virtio_ring.h
> > +++ b/include/uapi/linux/virtio_ring.h
>
> > /* Virtio ring descriptors: 16 bytes. These can chain together via
> > "next". */
> > struct vring_desc {
> > /* Address (guest-physical). */
> > - __u64 addr;
> > + __virtio64 addr;
>
> ... and __le64?
>
> There's already lots of precedence or this, even in include/uapi/.
>
> Gr{oetje,eeting}s,
>
> Geert
__le would make people think they can use le16-to_cpu() which is wrong.
--
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[PATCH v3 04/41] virtio: memory access APIs
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
Signed-off-by: Michael S. Tsirkin
---
include/linux/virtio_byteorder.h | 59 +++
include/linux/virtio_config.h | 32 +
include/uapi/linux/virtio_ring.h | 45 ++---
include/uapi/linux/virtio_types.h | 48 +++
include/uapi/linux/Kbuild | 1 +
5 files changed, 163 insertions(+), 22 deletions(-)
create mode 100644 include/linux/virtio_byteorder.h
create mode 100644 include/uapi/linux/virtio_types.h
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
@@ -0,0 +1,59 @@
+#ifndef _LINUX_VIRTIO_BYTEORDER_H
+#define _LINUX_VIRTIO_BYTEORDER_H
+#include
+#include
+
+/*
+ * Memory accessors for handling virtio in modern little endian and in
+ * compatibility native endian format.
+ */
+
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
+
+static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
+{
+ if (little_endian)
+ return (__force __virtio16)cpu_to_le16(val);
+ else
+ return (__force __virtio16)val;
+}
+
+static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
+{
+ if (little_endian)
+ return le32_to_cpu((__force __le32)val);
+ else
+ return (__force u32)val;
+}
+
+static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
+{
+ if (little_endian)
+ return (__force __virtio32)cpu_to_le32(val);
+ else
+ return (__force __virtio32)val;
+}
+
+static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
+{
+ if (little_endian)
+ return le64_to_cpu((__force __le64)val);
+ else
+ return (__force u64)val;
+}
+
+static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
+{
+ if (little_endian)
+ return (__force __virtio64)cpu_to_le64(val);
+ else
+ return (__force __virtio64)val;
+}
+
+#endif /* _LINUX_VIRTIO_BYTEORDER */
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 022d904..b9cd689 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -4,6 +4,7 @@
#include
#include
#include
+#include
#include
/**
@@ -152,6 +153,37 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
}
+/* Memory accessors */
+static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
+{
+ return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
+{
+ return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
+{
+ return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
+{
+ return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
+{
+ return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
+{
+ return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
/* Config space accessors. */
#define virtio_cread(vdev, structname, member, ptr)\
do {\
diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
index a99f9b7..61c818a 100644
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
@@ -32,6 +32,7 @@
*
* Copyright Rusty Russell IBM Corporation 2007. */
#include
+#include
/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT 1
@@ -61,32 +62,32 @@
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
- __u64 addr;
+ __virtio64 addr;
/* Length. */
- __u32 len;
+ __virtio32 len;
/* The flags as indicated
Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin wrote:
> virtio 1.0 makes all memory structures LE, so
> we need APIs to conditionally do a byteswap on BE
> architectures.
>
> To make it easier to check code statically,
> add virtio specific types for multi-byte integers
> in memory.
>
> Add low level wrappers that do a byteswap conditionally, these will be
> useful e.g. for vhost. Add high level wrappers that
> query device endian-ness and act accordingly.
> diff --git a/include/linux/virtio_byteorder.h
> b/include/linux/virtio_byteorder.h
> new file mode 100644
> index 000..824ed0b
> --- /dev/null
> +++ b/include/linux/virtio_byteorder.h
> +static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
> +{
> + if (little_endian)
> + return le16_to_cpu((__force __le16)val);
> + else
> + return (__force u16)val;
> +}
What's wrong with just using le16-to_cpu() ...
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> /* Virtio ring descriptors: 16 bytes. These can chain together via "next".
> */
> struct vring_desc {
> /* Address (guest-physical). */
> - __u64 addr;
> + __virtio64 addr;
... and __le64?
There's already lots of precedence or this, even in include/uapi/.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin m...@redhat.com wrote:
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
diff --git a/include/linux/virtio_byteorder.h
b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
What's wrong with just using le16-to_cpu() ...
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
/* Virtio ring descriptors: 16 bytes. These can chain together via next.
*/
struct vring_desc {
/* Address (guest-physical). */
- __u64 addr;
+ __virtio64 addr;
... and __le64?
There's already lots of precedence or this, even in include/uapi/.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say programmer or something like that.
-- Linus Torvalds
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH v3 04/41] virtio: memory access APIs
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
Signed-off-by: Michael S. Tsirkin m...@redhat.com
---
include/linux/virtio_byteorder.h | 59 +++
include/linux/virtio_config.h | 32 +
include/uapi/linux/virtio_ring.h | 45 ++---
include/uapi/linux/virtio_types.h | 48 +++
include/uapi/linux/Kbuild | 1 +
5 files changed, 163 insertions(+), 22 deletions(-)
create mode 100644 include/linux/virtio_byteorder.h
create mode 100644 include/uapi/linux/virtio_types.h
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
@@ -0,0 +1,59 @@
+#ifndef _LINUX_VIRTIO_BYTEORDER_H
+#define _LINUX_VIRTIO_BYTEORDER_H
+#include linux/types.h
+#include uapi/linux/virtio_types.h
+
+/*
+ * Memory accessors for handling virtio in modern little endian and in
+ * compatibility native endian format.
+ */
+
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
+
+static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
+{
+ if (little_endian)
+ return (__force __virtio16)cpu_to_le16(val);
+ else
+ return (__force __virtio16)val;
+}
+
+static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
+{
+ if (little_endian)
+ return le32_to_cpu((__force __le32)val);
+ else
+ return (__force u32)val;
+}
+
+static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
+{
+ if (little_endian)
+ return (__force __virtio32)cpu_to_le32(val);
+ else
+ return (__force __virtio32)val;
+}
+
+static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
+{
+ if (little_endian)
+ return le64_to_cpu((__force __le64)val);
+ else
+ return (__force u64)val;
+}
+
+static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
+{
+ if (little_endian)
+ return (__force __virtio64)cpu_to_le64(val);
+ else
+ return (__force __virtio64)val;
+}
+
+#endif /* _LINUX_VIRTIO_BYTEORDER */
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 022d904..b9cd689 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -4,6 +4,7 @@
#include linux/err.h
#include linux/bug.h
#include linux/virtio.h
+#include linux/virtio_byteorder.h
#include uapi/linux/virtio_config.h
/**
@@ -152,6 +153,37 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
}
+/* Memory accessors */
+static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
+{
+ return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
+{
+ return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
+{
+ return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
+{
+ return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
+{
+ return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
+static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
+{
+ return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1),
val);
+}
+
/* Config space accessors. */
#define virtio_cread(vdev, structname, member, ptr)\
do {\
diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
index a99f9b7..61c818a 100644
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
@@ -32,6 +32,7 @@
*
* Copyright Rusty Russell IBM Corporation 2007. */
#include linux/types.h
+#include linux/virtio_types.h
/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT 1
@@ -61,32 +62,32 @@
/* Virtio ring descriptors: 16 bytes. These can chain together via next. */
struct vring_desc {
/*
Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin m...@redhat.com wrote:
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
diff --git a/include/linux/virtio_byteorder.h
b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
What's wrong with just using le16-to_cpu() ...
le16-to_cpu() is simply wrong: virtio needs to be
LE or native endian, depending on whether it's running
in 0.9 or 1.0 mode.
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
/* Virtio ring descriptors: 16 bytes. These can chain together via
next. */
struct vring_desc {
/* Address (guest-physical). */
- __u64 addr;
+ __virtio64 addr;
... and __le64?
There's already lots of precedence or this, even in include/uapi/.
Gr{oetje,eeting}s,
Geert
__le would make people think they can use le16-to_cpu() which is wrong.
--
MST
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin m...@redhat.com wrote:
On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin m...@redhat.com wrote:
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
diff --git a/include/linux/virtio_byteorder.h
b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
What's wrong with just using le16-to_cpu() ...
le16-to_cpu() is simply wrong: virtio needs to be
LE or native endian, depending on whether it's running
in 0.9 or 1.0 mode.
IC, that was not clear from the description for this patch.
I thought it was dependent on BE architectures.
Nevertheless, any chance you can get rid of the conditional?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say programmer or something like that.
-- Linus Torvalds
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Re: [PATCH v3 04/41] virtio: memory access APIs
On Mon, Nov 24, 2014 at 01:58:43PM +0100, Geert Uytterhoeven wrote:
On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin m...@redhat.com wrote:
On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin m...@redhat.com
wrote:
virtio 1.0 makes all memory structures LE, so
we need APIs to conditionally do a byteswap on BE
architectures.
To make it easier to check code statically,
add virtio specific types for multi-byte integers
in memory.
Add low level wrappers that do a byteswap conditionally, these will be
useful e.g. for vhost. Add high level wrappers that
query device endian-ness and act accordingly.
diff --git a/include/linux/virtio_byteorder.h
b/include/linux/virtio_byteorder.h
new file mode 100644
index 000..824ed0b
--- /dev/null
+++ b/include/linux/virtio_byteorder.h
+static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
+{
+ if (little_endian)
+ return le16_to_cpu((__force __le16)val);
+ else
+ return (__force u16)val;
+}
What's wrong with just using le16-to_cpu() ...
le16-to_cpu() is simply wrong: virtio needs to be
LE or native endian, depending on whether it's running
in 0.9 or 1.0 mode.
IC, that was not clear from the description for this patch.
I thought it was dependent on BE architectures.
Nevertheless, any chance you can get rid of the conditional?
I don't see how - this is fundamental to any virtio device
that wants to support both 0.9 and 1.0 from the same
codebase.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say programmer or something like
that.
-- Linus Torvalds
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
