On Tue, Dec 29, 2015 at 11:01 PM, Alex Williamson <alex.william...@redhat.com> wrote: > On Tue, 2015-12-29 at 22:00 +0530, Santosh Shukla wrote: >> On Tue, Dec 29, 2015 at 9:50 PM, Arnd Bergmann <a...@arndb.de> wrote: >> > On Tuesday 29 December 2015 21:25:15 Santosh Shukla wrote: >> > > mistakenly added wrong email-id of alex, looping his correct one. >> > > >> > > On 29 December 2015 at 21:23, Santosh Shukla <santosh.shukla@lina >> > > ro.org> wrote: >> > > > On 29 December 2015 at 18:58, Arnd Bergmann <a...@arndb.de> >> > > > wrote: >> > > > > On Wednesday 23 December 2015 17:04:40 Santosh Shukla wrote: >> > > > > > On 23 December 2015 at 03:26, Arnd Bergmann <a...@arndb.de> >> > > > > > wrote: >> > > > > > > On Tuesday 22 December 2015, Santosh Shukla wrote: >> > > > > > > > } >> > > > > > > > >> > > > > > > > So I care for /dev/ioport types interface who could do >> > > > > > > > more than byte >> > > > > > > > data copy to/from user-space. I tested this patch with >> > > > > > > > little >> > > > > > > > modification and could able to run pmd driver for >> > > > > > > > arm/arm64 case. >> > > > > > > > >> > > > > > > > Like to know how to address pci_io region mapping >> > > > > > > > problem for >> > > > > > > > arm/arm64, in-case /dev/ioports approach is not >> > > > > > > > acceptable or else I >> > > > > > > > can spent time on restructuring the patch? >> > > > > > > > >> > > > > > > >> > > > > > > For the use case you describe, can't you use the vfio >> > > > > > > framework to >> > > > > > > access the PCI BARs? >> > > > > > > >> > > > > > >> > > > > > I looked at file: drivers/vfio/pci/vfio_pci.c, func >> > > > > > vfio_pci_map() and >> > > > > > it look to me that it only maps ioresource_mem pci region, >> > > > > > pasting >> > > > > > code snap: >> > > > > > >> > > > > > if (!(pci_resource_flags(pdev, index) & IORESOURCE_MEM)) >> > > > > > return -EINVAL; >> > > > > > .... >> > > > > > >> > > > > > and I want to map ioresource_io pci region for arm platform >> > > > > > in my >> > > > > > use-case. Not sure vfio maps pci_iobar region? >> > > > > >> > > > > Mapping I/O BARs is not portable, notably it doesn't work on >> > > > > x86. >> > > > > >> > > > > You should be able access them using the read/write interface >> > > > > on >> > > > > the vfio device. >> > > > > >> > > > Right, x86 doesn't care as iopl() could give userspace >> > > > application >> > > > direct access to ioports. >> > > > >> > > > Also, Alex in other dpdk thread [1] suggested someone to >> > > > propose io >> > > > bar mapping in vfio-pci, I guess in particular to non-x86 arch >> > > > so I >> > > > started working on it. >> > > > >> > > >> > >> > So what's wrong with just using the existing read/write API on all >> > architectures? >> > >> >> nothing wrong, infact read/write api will still be used so to access >> mmaped io pci bar at userspace. But right now vfio_pci_map() doesn't > > vfio_pci_mmap(), the read/write accessors fully support i/o port. >
(Sorry for delayed response!) Right. >> map io pci bar in particular (i.e.. ioresource_io) so I guess need to >> add that bar mapping in vfio. pl. correct me if i misunderstood >> anything. > > Maybe I misunderstood what you were asking for, it seemed like you > specifically wanted to be able to mmap i/o port space, which is > possible, just not something we can do on x86. Maybe I should have > asked why. The vfio API already supports read/write access to i/o port Yes, I want to map io port pci space in vfio and reason for that is : I want to access virto-net-pci device at userspace using vfio and for that I am using vfio-noiommu latest linux-next patch. but I am not able to mmap io port pci space in vfio because of below condition - 1) --- user space code snippet ---- reg.index = i; // where i is {0..1} i.e.. {BAR0..BAR1} such that BAR0 = io port pci space and BAR1 = pci config space ret = ioctl(vfio_dev_fd, VFIO_DEVICE_GET_REGION_INFO, ®); if ((reg.flags & VFIO_REGION_INFO_FLAG_MMAP) == 0) { return err; } now consider i = 0 case where pci_rersource_flag set to IORESOURCE_IO --- kernel / vfip-pci.c ------------- so vfio_pci_ioctl() wont set info.flag to VFIO_REGION_INFO_FLAG_MMAP. And it won't set for two 1) pci_resource_flag & IORESOURCE_MEM 2) ioport size < PAZE_SIZE The second one I addressed but first one is what I believe that need to add support in vfio. and Same applicable for vfio_pci_mmap() too.. This is why I am thinking to add IORESOURCE_IO space mapping support in vfio; in particular non-x86 archs.. pl. correct my understanding in case wrong. > space, so if you intend to mmap it only to use read/write on top of the > mmap, I suppose you might see some performance improvement, but not > really any new functionality. You'd also need to deal with page size > issues since i/o port ranges are generally quite a bit smaller than the > host page size and they'd need to be mapped such that each devices does > not share a host page of i/o port space with other devices. On x86 i/o Yes. I have taken care size < PAZE_SIZE condition. > port space is mostly considered legacy and not a performance critical > path for most modern devices; PCI SR-IOV specifically excludes i/o port > space. So what performance gains do you expect to see in being able to > mmap i/o port space and what hardware are you dealing with that relies > on i/o port space rather than mmio for performance? Thanks, > dpdk user space virtio-net pmd driver uses ioport space for driver initialization, as because virtio-net header resides in ioport area of virtio-pxe.rom file, also it is inlined to virtio spec (<= 0.95). Till now virtio-net dpdk pmd driver for x86 using iopl() to access those ioport for driver initialization but for non-x86 cases; we needed alternative i.e.. kernel to someway map ioport pci region either by architecture example powerpc does Or look in vfio for mapping. I hope I made my use-case clear. > Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/