On Tue, Jun 25, 2024 at 02:39:37PM -0400, sahanlb wrote: > PCI legacy configuration space does not have sufficient space for a device > that supports all kinds of virtio structures via PCI capabilities. This is > especially true if one were to use virtio drivers with physical devices. > Link: https://par.nsf.gov/servlets/purl/10463939 > A physical device may already have many capabilities in the legacy space. > > This patch adds support to place virtio capabilities in the PCI extended > configuration space and makes the driver search both legacy and extended > PCI configuration spaces. > > Add new argument to vp_modern_map_capability to indicate whether mapping > a legacy or extended capability. > Add new function virtio_pci_find_ext_capability to walk extended > capabilities and find virtio capabilities. > > Modify vp_modern_probe to search both legacy and extended configuration > spaces. > If virtio_pci_find_capability fails to find common, isr, notify, or device > virtio structures, call virtio_pci_find_ext_capability. > > Notify virtio structure can get mapped either in vp_modern_probe or in > vp_modern_map_vq_notify. Add new attribute 'notify_ecap' to > struct virtio_pci_modern_device to indicate whether the notify capability > is in the extended congiguration structure. > > Add virtio extended capability structures to > "include/uapi/linux/virtio_pci.h". > Format for the extended structures derived from > Link: https://lore.kernel.org/all/20220112055755.41011-2-jasowang@xxxxxxxxxx/ > > This patch has been validated using an FPGA development board to implement > a virtio interface. > > Signed-off-by: sahanlb <sahanb@xxxxxx> Thanks for the patch! As any UAPI change, this one has to also be accompanied by a spec patch documenting the capabilities. ... > +struct virtio_pci_cfg_ecap { > + struct virtio_pci_ecap cap; > + __u8 pci_cfg_data[4]; /* Data for BAR access. */ > +}; Hmm, a weird thing to do. The reason we have it is because a legacy bios has trouble accessing BAR directly (e.g. if BAR is 64 bit). Is there still an issue even for bios with support for pcie extended config space? > + > /* Macro versions of offsets for the Old Timers! */ > #define VIRTIO_PCI_CAP_VNDR 0 > #define VIRTIO_PCI_CAP_NEXT 1 This comes at an interesting time, there is an interest in order to get virtio working over EP protocol, in exposing all this information as part of a BAR as opposed as a capability. I wonder whether that's also palatable. > -- > 2.42.0
