On Wed, Mar 23, 2022 at 03:57:59PM +0800, Jason Wang wrote:
> On Tue, Mar 22, 2022 at 11:20 PM Keir Fraser <keirf@xxxxxxxxxx> wrote:
> >
> > The bar index is used as an index into the device's resource list
> > and should be checked as within range for a standard bar.
> >
> > Also clean up an existing check to consistently use PCI_STD_NUM_BARS.
> >
> > Signed-off-by: Keir Fraser <keirf@xxxxxxxxxx>
> > ---
> > drivers/virtio/virtio_pci_modern.c | 10 ++++++++--
> > drivers/virtio/virtio_pci_modern_dev.c | 8 +++++++-
> > 2 files changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 5455bc041fb6..84bace98dff5 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -293,7 +293,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> >
> > for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); pos > 0;
> > pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
> > - u8 type, cap_len, id;
> > + u8 type, cap_len, id, res_bar;
> > u32 tmp32;
> > u64 res_offset, res_length;
> >
> > @@ -317,7 +317,12 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> >
> > /* Type, and ID match, looks good */
> > pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> > - bar), bar);
> > + bar), &res_bar);
> > + if (res_bar >= PCI_STD_NUM_BARS) {
> > + dev_err(&dev->dev, "%s: shm cap with bad bar: %d\n",
> > + __func__, res_bar);
> > + continue;
> > + }
> >
> > /* Read the lower 32bit of length and offset */
> > pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap,
In fact, the spec says such BAR values are reserved, not bad, so
the capabiluty should be ignored, they should not cause the driver to error out
or print errors.
> > @@ -337,6 +342,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> > length_hi), &tmp32);
> > res_length |= ((u64)tmp32) << 32;
> >
> > + *bar = res_bar;
> > *offset = res_offset;
> > *len = res_length;
> >
> > diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> > index e8b3ff2b9fbc..a6911d1e212a 100644
> > --- a/drivers/virtio/virtio_pci_modern_dev.c
> > +++ b/drivers/virtio/virtio_pci_modern_dev.c
> > @@ -35,6 +35,12 @@ vp_modern_map_capability(struct virtio_pci_modern_device *mdev, int off,
> > pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, length),
> > &length);
> >
> > + if (bar >= PCI_STD_NUM_BARS) {
> > + dev_err(&dev->dev,
> > + "virtio_pci: bad capability bar %u\n", bar);
In fact, I would say the issue is less that bar is reserved.
The real issue is that the value apparently changed since
we read it the first time. I think it's a good idea to
reflect that in the message. Maybe find_capability should return
the capability structure so we don't need to re-read it from
the device?
> > + return NULL;
> > + }
> > +
> > if (length <= start) {
> > dev_err(&dev->dev,
> > "virtio_pci: bad capability len %u (>%u expected)\n",
> > @@ -120,7 +126,7 @@ static inline int virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type,
> > &bar);
> >
> > /* Ignore structures with reserved BAR values */
> > - if (bar > 0x5)
> > + if (bar >= PCI_STD_NUM_BARS)
> > continue;
>
> Just notice that the spec said:
>
> "
> values 0x0 to 0x5 specify a Base Address register (BAR) belonging to
> the function located beginning at 10h in PCI Configuration Space and
> used to map the structure into Memory or I/O Space. The BAR is
> permitted to be either 32-bit or 64-bit, it can map Memory Space or
> I/O Space.
>
> Any other value is reserved for future use.
> "
> So we probably need to stick 0x5 instead of 0x6 (PCI_STD_NUM_BARS) for
> this and other places.
>
> Thanks
It does not matter much IMHO, the reason spec uses 0 to 0x5 is precisely
because that's the standard number of BARs. Both ways work as long as we
are consistent, and I guess PCI_STD_NUM_BARS might be preferable since
people tend to copy paste values.
> >
> > if (type == cfg_type) {
> > --
> > 2.35.1.894.gb6a874cedc-goog
> >
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