On Tue, Oct 11, 2022 at 07:23:25PM +0800, Rui Ma wrote: > In some certain SR-IOV scene, when the device physical space(such as Video > RAM)is fixed, as the number of VFs increases, some device driver may decrease > actual BAR memory space used by each VF. However, the VF BAR memory mapping is > always based on the usual BAR probing algorithm in PCIe spec. So do not map this > unneeded memory can save host memory which occupied by PTEs. Although each PTE > only occupies a few bytes of space on its own, a large number of PTEs can still > take up a lot of space. Dropping this for now until we resolve whether this is working around a KVM bug as Alex suggests: https://lore.kernel.org/r/BL1PR12MB51446437265DD1E8AA0794E9F7239@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Rui Ma <Rui.Ma@xxxxxxx> > --- > drivers/pci/iov.c | 14 ++++++++++++-- > drivers/pci/pci.h | 15 +++++++++++++++ > drivers/pci/quirks.c | 37 +++++++++++++++++++++++++++++++++++++ > 3 files changed, 64 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index 952217572113..92a69e51d85c 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -296,6 +296,14 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id) > struct pci_sriov *iov = dev->sriov; > struct pci_bus *bus; > > + /* > + * Some SR-IOV device's BAR map range is larger than they can actually use. > + * This extra BAR space occupy too much reverse mapping size(physical page > + * back to the PTEs). So add a divisor shift parameter to resize the request > + * resource of VF according to num of VFs. > + */ > + u16 shift = 1; > + > bus = virtfn_add_bus(dev->bus, pci_iov_virtfn_bus(dev, id)); > if (!bus) > goto failed; > @@ -328,8 +336,10 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id) > virtfn->resource[i].name = pci_name(virtfn); > virtfn->resource[i].flags = res->flags; > size = pci_iov_resource_size(dev, i + PCI_IOV_RESOURCES); > + shift = 1; > + shift = virtfn_get_shift(dev, iov->num_VFs, i); > virtfn->resource[i].start = res->start + size * id; > - virtfn->resource[i].end = virtfn->resource[i].start + size - 1; > + virtfn->resource[i].end = virtfn->resource[i].start + (size >> (shift - 1)) - 1; > rc = request_resource(res, &virtfn->resource[i]); > BUG_ON(rc); > } > @@ -680,12 +690,12 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn) > msleep(100); > pci_cfg_access_unlock(dev); > > + iov->num_VFs = nr_virtfn; > rc = sriov_add_vfs(dev, initial); > if (rc) > goto err_pcibios; > > kobject_uevent(&dev->dev.kobj, KOBJ_CHANGE); > - iov->num_VFs = nr_virtfn; > > return 0; > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 3d60cabde1a1..befc67a280eb 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -603,6 +603,21 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, bool probe) > } > #endif > > +struct virtfn_get_shift_methods { > + u16 vendor; > + u16 device; > + u16 (*get_shift)(struct pci_dev *dev, u16 arg, int arg2); > +}; > + > +#ifdef CONFIG_PCI_QUIRKS > +u16 virtfn_get_shift(struct pci_dev *dev, u16 arg1, int arg2); > +#else > +static inline u16 virtfn_get_shift(struct pci_dev *dev, u16 arg1, int arg2) > +{ > + return (u16)1; > +} > +#endif > + > #if defined(CONFIG_PCI_QUIRKS) && defined(CONFIG_ARM64) > int acpi_get_rc_resources(struct device *dev, const char *hid, u16 segment, > struct resource *res); > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index da829274fc66..3466738c1c54 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -4085,6 +4085,43 @@ int pci_dev_specific_reset(struct pci_dev *dev, bool probe) > return -ENOTTY; > } > > +static u16 resize_vf_bar0(struct pci_dev *dev, u16 num_VFs, int bar_num) > +{ > + u16 shift = 1; > + > + if (bar_num == 0) { > + while ((1 << shift) <= num_VFs) > + shift += 1; > + } > + pci_info(dev, "with %d VFs, VF BAR%d get shift: %d\n", num_VFs, bar_num, shift); > + return shift; > +} > + > +static const struct virtfn_get_shift_methods virtfn_get_shift_methods[] = { > + { PCI_VENDOR_ID_ATI, 0x73a1, resize_vf_bar0}, > + { 0 } > +}; > + > +/* > + * Get shift num to calculate SR-IOV device BAR. Sometimes the BAR size for > + * SR-IOV device is too large and we want to calculate the size to define > + * the end of virtfn. > + */ > +u16 virtfn_get_shift(struct pci_dev *dev, u16 arg1, int arg2) > +{ > + const struct virtfn_get_shift_methods *i; > + > + for (i = virtfn_get_shift_methods; i->get_shift; i++) { > + if ((i->vendor == dev->vendor || > + i->vendor == (u16)PCI_ANY_ID) && > + (i->device == dev->device || > + i->device == (u16)PCI_ANY_ID)) > + return i->get_shift(dev, arg1, arg2); > + } > + > + return (u16)1; > +} > + > static void quirk_dma_func0_alias(struct pci_dev *dev) > { > if (PCI_FUNC(dev->devfn) != 0) > -- > 2.25.1 >
