* [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests
@ 2014-09-10 17:30 Michael S. Tsirkin
2014-09-11 16:00 ` Greg Kurz
0 siblings, 1 reply; 4+ messages in thread
From: Michael S. Tsirkin @ 2014-09-10 17:30 UTC (permalink / raw)
To: qemu-devel; +Cc: qemu-stable, Anthony Liguori
commit cc943c36faa192cd4b32af8fe5edb31894017d35
pci: Use bus master address space for delivering MSI/MSI-X messages
breaks virtio-net for rhel6.[56] x86 guests because they don't
enable bus mastering for virtio PCI devices
Old guests forgot to enable bus mastering, enable it
automatically when driver discovers device.
Cc: qemu-stable@nongnu.org
Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
OK, this should have better luck.
This also makes it possible to simplify code,
will do that in a follow-up patch.
hw/virtio/virtio-pci.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index ddb5da1..a29d94f 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -303,6 +303,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
virtio_pci_stop_ioeventfd(proxy);
}
+ /* Linux before 2.6.34 uses the device without enabling
+ the PCI device bus master bit. As a work-around, enable it
+ automatically when driver detects the device. */
+ if (val == VIRTIO_CONFIG_S_ACKNOWLEDGE) {
+ memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
+ true);
+ }
+
virtio_set_status(vdev, val & 0xFF);
if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
--
MST
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests
2014-09-10 17:30 [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests Michael S. Tsirkin
@ 2014-09-11 16:00 ` Greg Kurz
2014-09-11 16:49 ` Michael S. Tsirkin
2014-09-11 17:52 ` Michael S. Tsirkin
0 siblings, 2 replies; 4+ messages in thread
From: Greg Kurz @ 2014-09-11 16:00 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: qemu-devel, Anthony Liguori, qemu-stable
On Wed, 10 Sep 2014 20:30:47 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> commit cc943c36faa192cd4b32af8fe5edb31894017d35
> pci: Use bus master address space for delivering MSI/MSI-X messages
> breaks virtio-net for rhel6.[56] x86 guests because they don't
> enable bus mastering for virtio PCI devices
>
> Old guests forgot to enable bus mastering, enable it
> automatically when driver discovers device.
>
> Cc: qemu-stable@nongnu.org
> Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> OK, this should have better luck.
Unfortunately not... it is even worse than V1 as
both x86 and ppc64 guests fail. I've added some
debug messages in virtio_ioport_write() and
virtio_write_config() to track:
- VIRTIO_PCI_STATUS changes
- bus master disablement
This is what I get for x86 with a virtio-net device:
virtio_write_config: PCI_COMMAND = 0x3
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x7
virtio_ioport_write: detected bus master bug ==> v1 patch would have
enabled BM here
and for ppc64 when booting from a virtio-blk disk:
virtio_write_config: PCI_COMMAND = 0x3
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
I think we should:
- detect the "old driver" when reaching DRIVER as it works for
both architectures
- always re-enable BM when an "old driver" disables it
That is basically your v1 plus its follow-up patch:
https://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg01918.html
plus:
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -317,7 +317,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
/* Linux before 2.6.34 sets the device as OK without enabling
the PCI device bus master bit. In this case we need to disable
some safety checks. */
- if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
+ if ((val & VIRTIO_CONFIG_S_DRIVER) &&
!(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
I could verify it fixes the issues. I will send a patch shortly.
Cheers.
--
Greg
> This also makes it possible to simplify code,
> will do that in a follow-up patch.
>
>
> hw/virtio/virtio-pci.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index ddb5da1..a29d94f 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -303,6 +303,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> virtio_pci_stop_ioeventfd(proxy);
> }
>
> + /* Linux before 2.6.34 uses the device without enabling
> + the PCI device bus master bit. As a work-around, enable it
> + automatically when driver detects the device. */
> + if (val == VIRTIO_CONFIG_S_ACKNOWLEDGE) {
> + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> + true);
> + }
> +
> virtio_set_status(vdev, val & 0xFF);
>
> if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests
2014-09-11 16:00 ` Greg Kurz
@ 2014-09-11 16:49 ` Michael S. Tsirkin
2014-09-11 17:52 ` Michael S. Tsirkin
1 sibling, 0 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2014-09-11 16:49 UTC (permalink / raw)
To: Greg Kurz; +Cc: qemu-devel, Anthony Liguori, qemu-stable
On Thu, Sep 11, 2014 at 06:00:39PM +0200, Greg Kurz wrote:
> On Wed, 10 Sep 2014 20:30:47 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > commit cc943c36faa192cd4b32af8fe5edb31894017d35
> > pci: Use bus master address space for delivering MSI/MSI-X messages
> > breaks virtio-net for rhel6.[56] x86 guests because they don't
> > enable bus mastering for virtio PCI devices
> >
> > Old guests forgot to enable bus mastering, enable it
> > automatically when driver discovers device.
> >
> > Cc: qemu-stable@nongnu.org
> > Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > OK, this should have better luck.
>
> Unfortunately not... it is even worse than V1 as
> both x86 and ppc64 guests fail. I've added some
> debug messages in virtio_ioport_write() and
> virtio_write_config() to track:
> - VIRTIO_PCI_STATUS changes
> - bus master disablement
>
> This is what I get for x86 with a virtio-net device:
>
> virtio_write_config: PCI_COMMAND = 0x3
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
> virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
Weird. What code in guest causes this second write?
Any idea?
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x7
> virtio_ioport_write: detected bus master bug ==> v1 patch would have
> enabled BM here
>
> and for ppc64 when booting from a virtio-blk disk:
>
> virtio_write_config: PCI_COMMAND = 0x3
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
> virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
>
> I think we should:
> - detect the "old driver" when reaching DRIVER as it works for
> both architectures
Basically take v2 and replace ACKNOWLEDGE with DRIVER.
Yea, maybe.
But I would like to understand what is going on here.
> - always re-enable BM when an "old driver" disables it
>
> That is basically your v1 plus its follow-up patch:
>
> https://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg01918.html
>
> plus:
>
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -317,7 +317,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> /* Linux before 2.6.34 sets the device as OK without enabling
> the PCI device bus master bit. In this case we need to disable
> some safety checks. */
> - if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> + if ((val & VIRTIO_CONFIG_S_DRIVER) &&
> !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
>
> I could verify it fixes the issues. I will send a patch shortly.
>
>
> Cheers.
>
> --
> Greg
>
> > This also makes it possible to simplify code,
> > will do that in a follow-up patch.
> >
> >
> > hw/virtio/virtio-pci.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index ddb5da1..a29d94f 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -303,6 +303,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> > virtio_pci_stop_ioeventfd(proxy);
> > }
> >
> > + /* Linux before 2.6.34 uses the device without enabling
> > + the PCI device bus master bit. As a work-around, enable it
> > + automatically when driver detects the device. */
> > + if (val == VIRTIO_CONFIG_S_ACKNOWLEDGE) {
> > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> > + true);
> > + }
> > +
> > virtio_set_status(vdev, val & 0xFF);
> >
> > if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests
2014-09-11 16:00 ` Greg Kurz
2014-09-11 16:49 ` Michael S. Tsirkin
@ 2014-09-11 17:52 ` Michael S. Tsirkin
1 sibling, 0 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2014-09-11 17:52 UTC (permalink / raw)
To: Greg Kurz; +Cc: qemu-devel, Anthony Liguori, qemu-stable
On Thu, Sep 11, 2014 at 06:00:39PM +0200, Greg Kurz wrote:
> On Wed, 10 Sep 2014 20:30:47 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > commit cc943c36faa192cd4b32af8fe5edb31894017d35
> > pci: Use bus master address space for delivering MSI/MSI-X messages
> > breaks virtio-net for rhel6.[56] x86 guests because they don't
> > enable bus mastering for virtio PCI devices
> >
> > Old guests forgot to enable bus mastering, enable it
> > automatically when driver discovers device.
> >
> > Cc: qemu-stable@nongnu.org
> > Reported-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > OK, this should have better luck.
>
> Unfortunately not... it is even worse than V1 as
> both x86 and ppc64 guests fail. I've added some
> debug messages in virtio_ioport_write() and
> virtio_write_config() to track:
> - VIRTIO_PCI_STATUS changes
> - bus master disablement
>
> This is what I get for x86 with a virtio-net device:
>
> virtio_write_config: PCI_COMMAND = 0x3
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
> virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x7
> virtio_ioport_write: detected bus master bug ==> v1 patch would have
> enabled BM here
>
> and for ppc64 when booting from a virtio-blk disk:
>
> virtio_write_config: PCI_COMMAND = 0x3
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x0
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x1 ==> v2 patch enables BM
> virtio_ioport_write: VIRTIO_PCI_STATUS = 0x3
> virtio_write_config: PCI_COMMAND = 0x3 ==> guest disables BM
So guest sets DRIVER then overwrites PCI_COMMAND. Weird.
Any idea which guest code does this?
> I think we should:
> - detect the "old driver" when reaching DRIVER as it works for
> both architectures
> - always re-enable BM when an "old driver" disables it
>
> That is basically your v1 plus its follow-up patch:
>
> https://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg01918.html
>
> plus:
>
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -317,7 +317,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> /* Linux before 2.6.34 sets the device as OK without enabling
> the PCI device bus master bit. In this case we need to disable
> some safety checks. */
> - if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> + if ((val & VIRTIO_CONFIG_S_DRIVER) &&
> !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
>
> I could verify it fixes the issues. I will send a patch shortly.
>
>
> Cheers.
>
> --
> Greg
>
> > This also makes it possible to simplify code,
> > will do that in a follow-up patch.
> >
> >
> > hw/virtio/virtio-pci.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index ddb5da1..a29d94f 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -303,6 +303,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> > virtio_pci_stop_ioeventfd(proxy);
> > }
> >
> > + /* Linux before 2.6.34 uses the device without enabling
> > + the PCI device bus master bit. As a work-around, enable it
> > + automatically when driver detects the device. */
> > + if (val == VIRTIO_CONFIG_S_ACKNOWLEDGE) {
> > + memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> > + true);
> > + }
> > +
> > virtio_set_status(vdev, val & 0xFF);
> >
> > if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
^ permalink raw reply [flat|nested] 4+ messages in thread
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2014-09-10 17:30 [Qemu-devel] [PATCH v2] virtio-pci: enable bus master for old guests Michael S. Tsirkin
2014-09-11 16:00 ` Greg Kurz
2014-09-11 16:49 ` Michael S. Tsirkin
2014-09-11 17:52 ` Michael S. Tsirkin
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