* [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk
@ 2013-05-28 10:11 Michael S. Tsirkin
2013-05-28 10:14 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2013-05-28 10:11 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Anthony Liguori, agraf, blauwirbel, Paolo Bonzini,
KONRAD Frederic
When a BE guest reads capacity from an LE host virtio-blk device or vice
versa, it will get the dwords of the qword field swapped.
As virtio-blk is the only one with such a quirk,
and as non-pci transports don't do byte-swaps at all,
solve this with a bit of device-specific hackery in
virtio-pci.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
I don't seem to be able to boot any big-endian
guests ATM, so this is only compile-tested - sending
this out for early feedback/flames.
Testing reports also wellcome!
hw/virtio/virtio-pci.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 9668b2b..0e9ae4c 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -411,6 +411,15 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr,
}
break;
case 4:
+ /* Most devices don't have 64 bit config fields.
+ * Block is an exception: first 8 bytes include
+ * a 64 bit capacity field.
+ */
+ if (virtio_is_big_endian() != defined(HOST_WORDS_BIGENDIAN) &&
+ proxy->vdev->dev_id == VIRTIO_ID_BLOCK && addr < 8) {
+ /* Swap first two words */
+ addr ^= 0x4;
+ }
val = virtio_config_readl(proxy->vdev, addr);
if (virtio_is_big_endian()) {
val = bswap32(val);
--
MST
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk
2013-05-28 10:11 [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk Michael S. Tsirkin
@ 2013-05-28 10:14 ` Paolo Bonzini
2013-05-28 10:38 ` Michael S. Tsirkin
0 siblings, 1 reply; 3+ messages in thread
From: Paolo Bonzini @ 2013-05-28 10:14 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Peter Maydell, Anthony Liguori, agraf, qemu-devel, blauwirbel,
KONRAD Frederic
Il 28/05/2013 12:11, Michael S. Tsirkin ha scritto:
> When a BE guest reads capacity from an LE host virtio-blk device or vice
> versa, it will get the dwords of the qword field swapped.
> As virtio-blk is the only one with such a quirk,
> and as non-pci transports don't do byte-swaps at all,
> solve this with a bit of device-specific hackery in
> virtio-pci.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> I don't seem to be able to boot any big-endian
> guests ATM, so this is only compile-tested - sending
> this out for early feedback/flames.
> Testing reports also wellcome!
>
> hw/virtio/virtio-pci.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 9668b2b..0e9ae4c 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -411,6 +411,15 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr,
> }
> break;
> case 4:
> + /* Most devices don't have 64 bit config fields.
> + * Block is an exception: first 8 bytes include
> + * a 64 bit capacity field.
> + */
> + if (virtio_is_big_endian() != defined(HOST_WORDS_BIGENDIAN) &&
I thought think this is not valid C?
Paolo
> + proxy->vdev->dev_id == VIRTIO_ID_BLOCK && addr < 8) {
> + /* Swap first two words */
> + addr ^= 0x4;
> + }
> val = virtio_config_readl(proxy->vdev, addr);
> if (virtio_is_big_endian()) {
> val = bswap32(val);
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk
2013-05-28 10:14 ` Paolo Bonzini
@ 2013-05-28 10:38 ` Michael S. Tsirkin
0 siblings, 0 replies; 3+ messages in thread
From: Michael S. Tsirkin @ 2013-05-28 10:38 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Peter Maydell, Anthony Liguori, agraf, qemu-devel, blauwirbel,
KONRAD Frederic
On Tue, May 28, 2013 at 12:14:59PM +0200, Paolo Bonzini wrote:
> Il 28/05/2013 12:11, Michael S. Tsirkin ha scritto:
> > When a BE guest reads capacity from an LE host virtio-blk device or vice
> > versa, it will get the dwords of the qword field swapped.
> > As virtio-blk is the only one with such a quirk,
> > and as non-pci transports don't do byte-swaps at all,
> > solve this with a bit of device-specific hackery in
> > virtio-pci.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > I don't seem to be able to boot any big-endian
> > guests ATM, so this is only compile-tested - sending
> > this out for early feedback/flames.
> > Testing reports also wellcome!
> >
> > hw/virtio/virtio-pci.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 9668b2b..0e9ae4c 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -411,6 +411,15 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr,
> > }
> > break;
> > case 4:
> > + /* Most devices don't have 64 bit config fields.
> > + * Block is an exception: first 8 bytes include
> > + * a 64 bit capacity field.
> > + */
> > + if (virtio_is_big_endian() != defined(HOST_WORDS_BIGENDIAN) &&
>
> I thought think this is not valid C?
>
> Paolo
Yes, v2 I just sent fixes this.
Thanks for paying attention.
> > + proxy->vdev->dev_id == VIRTIO_ID_BLOCK && addr < 8) {
> > + /* Swap first two words */
> > + addr ^= 0x4;
> > + }
> > val = virtio_config_readl(proxy->vdev, addr);
> > if (virtio_is_big_endian()) {
> > val = bswap32(val);
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-05-28 10:38 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-05-28 10:11 [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk Michael S. Tsirkin
2013-05-28 10:14 ` Paolo Bonzini
2013-05-28 10:38 ` Michael S. Tsirkin
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.