On Tue, 14 Nov 2023 13:46:11 +0530 <ankita@xxxxxxxxxx> wrote: > From: Ankit Agrawal <ankita@xxxxxxxxxx> > > NVIDIA's upcoming Grace Hopper Superchip provides a PCI-like device > for the on-chip GPU that is the logical OS representation of the > internal proprietary chip-to-chip cache coherent interconnect. > > The device is peculiar compared to a real PCI device in that whilst > there is a real 64b PCI BAR1 (comprising region 2 & region 3) on the device, > it is not used to access device memory once the faster chip-to-chip > interconnect is initialized (occurs at the time of host system boot). > The device memory is accessed instead using the chip-to-chip interconnect > that is exposed as a contiguous physically addressable region on the host. > > Provide a VFIO PCI variant driver that adapts the unique device memory > representation into a more standard PCI representation facing userspace. > > The device memory aperture is obtained from ACPI using > device_property_read_u64(), according to the FW specification, and exported > to userspace as a separate VFIO BAR region. Since the device implements > 64-bit BAR0, the VFIO PCI variant driver maps the GPU memory aperture > to the next available PCI BAR (BAR2). Qemu will then naturally generate a > PCI device in the VM with the cacheable aperture reported in BAR2 region. The > variant driver also provides emulation for this fake BAR's PCI config space > offset registers. > > Since this memory region is actually cache coherent with the CPU, the > VFIO variant driver will mmap it into VMA using a cacheable mapping. The > mapping is done using remap_pfn_range(). > > PCI BAR are aligned to the power-of-2, but the actual memory on the > device may not. A read or write access to the physical address from the > last device PFN up to the next power-of-2 aligned physical address > results in reading ~0 and dropped writes. Note that the GPU device > driver [1] is capable of knowing the exact device memory size through > separate means. The device memory size is primarily kept in the system > ACPI tables for use by the VFIO PCI variant module. > > This goes along with a qemu series to provides the necessary > implementation of the Grace Hopper Superchip firmware specification so > that the guest operating system can see the correct ACPI modeling for > the coherent GPU device. Verified with the CUDA workload in the VM. > https://lore.kernel.org/all/20231107190039.19434-1-ankita@xxxxxxxxxx/ > > This patch is split from a patch series being pursued separately: > https://lore.kernel.org/lkml/20230405180134.16932-1-ankita@xxxxxxxxxx/ > > Applied over next-20231113. > > [1] https://github.com/NVIDIA/open-gpu-kernel-modules > > Signed-off-by: Ankit Agrawal <ankita@xxxxxxxxxx> > Signed-off-by: Aniket Agashe <aniketa@xxxxxxxxxx> > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> There's been a fair bit of churn since Kevin's ack, probably best to drop this until he provides a more recent review. > --- > > Link for v12: > https://lore.kernel.org/all/20231015163047.20391-1-ankita@xxxxxxxxxx/ > > v12 -> v13 > - Added emulation for the PCI config space BAR offset register for > the fake BAR. > - commit message updated with more details on the BAR offset emulation. > > v11 -> v12 > - More details in commit message on device memory size > > v10 -> v11 > - Removed sysfs attribute to expose the CPU coherent memory feature > - Addressed review comments > > v9 -> v10 > - Add new sysfs attribute to expose the CPU coherent memory feature. > > v8 -> v9 > - Minor code adjustment suggested in v8. > > v7 -> v8 > - Various field names updated. > - Added a new function to handle VFIO_DEVICE_GET_REGION_INFO ioctl. > - Locking protection for memremap to bar region and other changes > recommended in v7. > - Added code to fail if the devmem size advertized is 0 in system DSDT. > > v6 -> v7 > - Handled out-of-bound and overflow conditions at various places to validate > input offset and length. > - Added code to return EINVAL for offset beyond region size. > > v5 -> v6 > - Added the code to handle BAR2 read/write using memremap to the device > memory. > > v4 -> v5 > - Changed the module name from nvgpu-vfio-pci to nvgrace-gpu-vfio-pci. > - Fixed memory leak and added suggested boundary checks on device memory > mapping. > - Added code to read all Fs and ignored write on region outside of the > physical memory. > - Other miscellaneous cleanup suggestions. > > v3 -> v4 > - Mapping the available device memory using sparse mmap. The region outside > the device memory is handled by read/write ops. > - Removed the fault handler added in v3. > > v2 -> v3 > - Added fault handler to map the region outside the physical GPU memory > up to the next power-of-2 to a dummy PFN. > - Changed to select instead of "depends on" VFIO_PCI_CORE for all the > vfio-pci variant driver. > - Code cleanup based on feedback comments. > - Code implemented and tested against v6.4-rc4. > > v1 -> v2 > - Updated the wording of reference to BAR offset and replaced with > index. > - The GPU memory is exposed at the fixed BAR2_REGION_INDEX. > - Code cleanup based on feedback comments. > --- > --- > MAINTAINERS | 6 + > drivers/vfio/pci/Kconfig | 2 + > drivers/vfio/pci/Makefile | 2 + > drivers/vfio/pci/nvgrace-gpu/Kconfig | 10 + > drivers/vfio/pci/nvgrace-gpu/Makefile | 3 + > drivers/vfio/pci/nvgrace-gpu/main.c | 586 ++++++++++++++++++++++++++ > 6 files changed, 609 insertions(+) > create mode 100644 drivers/vfio/pci/nvgrace-gpu/Kconfig > create mode 100644 drivers/vfio/pci/nvgrace-gpu/Makefile > create mode 100644 drivers/vfio/pci/nvgrace-gpu/main.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 1466699fbaaf..c1b43eb35cea 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -22891,6 +22891,12 @@ L: kvm@xxxxxxxxxxxxxxx > S: Maintained > F: drivers/vfio/platform/ > > +VFIO NVIDIA GRACE GPU DRIVER > +M: Ankit Agrawal <ankita@xxxxxxxxxx> > +L: kvm@xxxxxxxxxxxxxxx > +S: Maintained > +F: drivers/vfio/pci/nvgrace-gpu/ > + > VGA_SWITCHEROO > R: Lukas Wunner <lukas@xxxxxxxxx> > S: Maintained > diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig > index 8125e5f37832..2456210e85f1 100644 > --- a/drivers/vfio/pci/Kconfig > +++ b/drivers/vfio/pci/Kconfig > @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig" > > source "drivers/vfio/pci/pds/Kconfig" > > +source "drivers/vfio/pci/nvgrace-gpu/Kconfig" > + > endmenu > diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile > index 45167be462d8..1352c65e568a 100644 > --- a/drivers/vfio/pci/Makefile > +++ b/drivers/vfio/pci/Makefile > @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI) += mlx5/ > obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/ > > obj-$(CONFIG_PDS_VFIO_PCI) += pds/ > + > +obj-$(CONFIG_NVGRACE_GPU_VFIO_PCI) += nvgrace-gpu/ > diff --git a/drivers/vfio/pci/nvgrace-gpu/Kconfig b/drivers/vfio/pci/nvgrace-gpu/Kconfig > new file mode 100644 > index 000000000000..936e88d8d41d > --- /dev/null > +++ b/drivers/vfio/pci/nvgrace-gpu/Kconfig > @@ -0,0 +1,10 @@ > +# SPDX-License-Identifier: GPL-2.0-only > +config NVGRACE_GPU_VFIO_PCI > + tristate "VFIO support for the GPU in the NVIDIA Grace Hopper Superchip" > + depends on ARM64 || (COMPILE_TEST && 64BIT) > + select VFIO_PCI_CORE > + help > + VFIO support for the GPU in the NVIDIA Grace Hopper Superchip is > + required to assign the GPU device using KVM/qemu/etc. > + > + If you don't know what to do here, say N. > diff --git a/drivers/vfio/pci/nvgrace-gpu/Makefile b/drivers/vfio/pci/nvgrace-gpu/Makefile > new file mode 100644 > index 000000000000..3ca8c187897a > --- /dev/null > +++ b/drivers/vfio/pci/nvgrace-gpu/Makefile > @@ -0,0 +1,3 @@ > +# SPDX-License-Identifier: GPL-2.0-only > +obj-$(CONFIG_NVGRACE_GPU_VFIO_PCI) += nvgrace-gpu-vfio-pci.o > +nvgrace-gpu-vfio-pci-y := main.o > diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c > new file mode 100644 > index 000000000000..a3dbee6b87de > --- /dev/null > +++ b/drivers/vfio/pci/nvgrace-gpu/main.c > @@ -0,0 +1,586 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved > + */ > + > +#include <linux/pci.h> > +#include <linux/vfio_pci_core.h> > +#include <linux/vfio.h> > + > +struct nvgrace_gpu_vfio_pci_core_device { > + struct vfio_pci_core_device core_device; > + phys_addr_t memphys; > + size_t memlength; > + u32 bar_regs[2]; > + void *memmap; > + struct mutex memmap_lock; > +}; > + > +static void init_fake_bar_emu_regs(struct vfio_device *core_vdev) > +{ > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, > + core_device.vdev); > + > + nvdev->bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 | > + PCI_BASE_ADDRESS_MEM_PREFETCH; > + nvdev->bar_regs[1] = 0; > +} > + > +static bool is_fake_bar_pcicfg_emu_reg_access(loff_t pos) > +{ > + unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(pos); > + u64 offset = pos & VFIO_PCI_OFFSET_MASK; > + > + if ((index == VFIO_PCI_CONFIG_REGION_INDEX) && > + (offset == PCI_BASE_ADDRESS_2 || offset == PCI_BASE_ADDRESS_3)) > + return true; What spec reference do you have that suggests that config space can only be accessed at double word alignment? > + > + return false; > +} > + > +static int nvgrace_gpu_vfio_pci_open_device(struct vfio_device *core_vdev) > +{ > + struct vfio_pci_core_device *vdev = > + container_of(core_vdev, struct vfio_pci_core_device, vdev); > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, > + core_device.vdev); > + int ret; > + > + ret = vfio_pci_core_enable(vdev); > + if (ret) > + return ret; > + > + vfio_pci_core_finish_enable(vdev); > + > + init_fake_bar_emu_regs(core_vdev); > + > + mutex_init(&nvdev->memmap_lock); > + > + return 0; > +} > + > +static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev) > +{ > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, > + core_device.vdev); > + > + if (nvdev->memmap) { > + memunmap(nvdev->memmap); > + nvdev->memmap = NULL; > + } > + > + mutex_destroy(&nvdev->memmap_lock); > + > + vfio_pci_core_close_device(core_vdev); > +} > + > +static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev, > + struct vm_area_struct *vma) > +{ > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev); > + > + unsigned long start_pfn; > + unsigned int index; > + u64 req_len, pgoff, end; > + int ret = 0; > + > + index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT); > + if (index != VFIO_PCI_BAR2_REGION_INDEX) > + return vfio_pci_core_mmap(core_vdev, vma); > + > + /* > + * Request to mmap the BAR. Map to the CPU accessible memory on the > + * GPU using the memory information gathered from the system ACPI > + * tables. > + */ > + pgoff = vma->vm_pgoff & > + ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); > + > + if (check_sub_overflow(vma->vm_end, vma->vm_start, &req_len) || > + check_add_overflow(PHYS_PFN(nvdev->memphys), pgoff, &start_pfn) || > + check_add_overflow(PFN_PHYS(pgoff), req_len, &end)) > + return -EOVERFLOW; > + > + /* > + * Check that the mapping request does not go beyond available device > + * memory size > + */ > + if (end > nvdev->memlength) > + return -EINVAL; > + > + /* > + * Perform a PFN map to the memory and back the device BAR by the > + * GPU memory. > + * > + * The available GPU memory size may not be power-of-2 aligned. Map up > + * to the size of the device memory. If the memory access is beyond the > + * actual GPU memory size, it will be handled by the vfio_device_ops > + * read/write. > + * > + * During device reset, the GPU is safely disconnected to the CPU > + * and access to the BAR will be immediately returned preventing > + * machine check. > + */ > + ret = remap_pfn_range(vma, vma->vm_start, start_pfn, > + req_len, vma->vm_page_prot); > + if (ret) > + return ret; > + > + vma->vm_pgoff = start_pfn; > + > + return 0; > +} > + > +static long > +nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev, > + unsigned long arg) > +{ > + unsigned long minsz = offsetofend(struct vfio_region_info, offset); > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev); > + struct vfio_region_info info; > + > + if (copy_from_user(&info, (void __user *)arg, minsz)) > + return -EFAULT; > + > + if (info.argsz < minsz) > + return -EINVAL; > + > + if (info.index == VFIO_PCI_BAR2_REGION_INDEX) { > + /* > + * Request to determine the BAR region information. Send the > + * GPU memory information. > + */ > + uint32_t size; > + int ret; > + struct vfio_region_info_cap_sparse_mmap *sparse; > + struct vfio_info_cap caps = { .buf = NULL, .size = 0 }; > + > + size = struct_size(sparse, areas, 1); > + > + /* > + * Setup for sparse mapping for the device memory. Only the > + * available device memory on the hardware is shown as a > + * mappable region. > + */ > + sparse = kzalloc(size, GFP_KERNEL); > + if (!sparse) > + return -ENOMEM; > + > + sparse->nr_areas = 1; > + sparse->areas[0].offset = 0; > + sparse->areas[0].size = nvdev->memlength; > + sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP; > + sparse->header.version = 1; > + > + ret = vfio_info_add_capability(&caps, &sparse->header, size); > + kfree(sparse); > + if (ret) > + return ret; > + > + info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index); > + /* > + * The available GPU memory size may not be power-of-2 aligned. > + * Given that the memory is exposed as a BAR and may not be > + * aligned, roundup to the next power-of-2. > + */ > + info.size = roundup_pow_of_two(nvdev->memlength); > + info.flags = VFIO_REGION_INFO_FLAG_READ | > + VFIO_REGION_INFO_FLAG_WRITE | > + VFIO_REGION_INFO_FLAG_MMAP; > + > + if (caps.size) { > + info.flags |= VFIO_REGION_INFO_FLAG_CAPS; > + if (info.argsz < sizeof(info) + caps.size) { > + info.argsz = sizeof(info) + caps.size; > + info.cap_offset = 0; > + } else { > + vfio_info_cap_shift(&caps, sizeof(info)); > + if (copy_to_user((void __user *)arg + > + sizeof(info), caps.buf, > + caps.size)) { > + kfree(caps.buf); > + return -EFAULT; > + } > + info.cap_offset = sizeof(info); > + } > + kfree(caps.buf); > + } > + return copy_to_user((void __user *)arg, &info, minsz) ? > + -EFAULT : 0; > + } > + return vfio_pci_core_ioctl(core_vdev, VFIO_DEVICE_GET_REGION_INFO, arg); > +} > + > +static long nvgrace_gpu_vfio_pci_ioctl(struct vfio_device *core_vdev, > + unsigned int cmd, unsigned long arg) > +{ > + if (cmd == VFIO_DEVICE_GET_REGION_INFO) > + return nvgrace_gpu_vfio_pci_ioctl_get_region_info(core_vdev, arg); > + > + if (cmd == VFIO_DEVICE_RESET) > + init_fake_bar_emu_regs(core_vdev); > + > + return vfio_pci_core_ioctl(core_vdev, cmd, arg); > +} > + > +static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev) > +{ > + mutex_lock(&nvdev->memmap_lock); > + if (!nvdev->memmap) { > + nvdev->memmap = memremap(nvdev->memphys, nvdev->memlength, MEMREMAP_WB); > + if (!nvdev->memmap) { > + mutex_unlock(&nvdev->memmap_lock); > + return -ENOMEM; > + } > + } > + mutex_unlock(&nvdev->memmap_lock); > + > + return 0; > +} > + > +/* > + * Read count bytes from the device memory at an offset. The actual device > + * memory size (available) may not be a power-of-2. So the driver fakes > + * the size to a power-of-2 (reported) when exposing to a user space driver. > + * > + * Read request beyond the actual device size is filled with ~0, while > + * those beyond the actual reported size is skipped. > + * > + * A read from a negative or an offset greater than reported size, a negative > + * count are considered error conditions and returned with an -EINVAL. > + */ > +static ssize_t > +nvgrace_gpu_read_mem(void __user *buf, size_t count, loff_t *ppos, > + struct nvgrace_gpu_vfio_pci_core_device *nvdev) > +{ > + u64 offset = *ppos & VFIO_PCI_OFFSET_MASK; > + size_t mem_count, i, bar_size = roundup_pow_of_two(nvdev->memlength); > + u8 val = 0xFF; > + > + if (offset >= bar_size) > + return -EINVAL; > + > + /* Clip short the read request beyond reported BAR size */ > + count = min(count, bar_size - (size_t)offset); > + > + /* > + * Determine how many bytes to be actually read from the device memory. > + * Read request beyond the actual device memory size is filled with ~0, > + * while those beyond the actual reported size is skipped. > + */ > + if (offset >= nvdev->memlength) > + mem_count = 0; > + else > + mem_count = min(count, nvdev->memlength - (size_t)offset); > + > + /* > + * Handle read on the BAR2 region. Map to the target device memory > + * physical address and copy to the request read buffer. > + */ > + if (copy_to_user(buf, (u8 *)nvdev->memmap + offset, mem_count)) > + return -EFAULT; > + > + /* > + * Only the device memory present on the hardware is mapped, which may > + * not be power-of-2 aligned. A read to an offset beyond the device memory > + * size is filled with ~0. > + */ > + for (i = mem_count; i < count; i++) > + put_user(val, (unsigned char __user *)(buf + i)); > + > + *ppos += count; > + return count; > +} > + > +static ssize_t pcibar_read_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev, > + char __user *buf, size_t count, loff_t *ppos) > +{ > + u64 pos = *ppos & VFIO_PCI_OFFSET_MASK; > + u32 val; > + > + if (!IS_ALIGNED(pos, 4) || !(is_fake_bar_pcicfg_emu_reg_access(*ppos))) > + return -EINVAL; Isn't the latter redundant to the caller? Unnecessary () in the latter too. > + > + switch (pos) { > + case PCI_BASE_ADDRESS_2: > + val = nvdev->bar_regs[0]; > + break; > + case PCI_BASE_ADDRESS_3: > + val = nvdev->bar_regs[1]; > + break; > + } > + > + if (copy_to_user(buf, &val, count)) > + return -EFAULT; > + > + *ppos += count; > + return count; > +} > + > +static ssize_t nvgrace_gpu_vfio_pci_read(struct vfio_device *core_vdev, > + char __user *buf, size_t count, loff_t *ppos) > +{ > + unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos); > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, > + core_device.vdev); > + int ret; > + > + if (index == VFIO_PCI_BAR2_REGION_INDEX) { > + ret = nvgrace_gpu_memmap(nvdev); > + if (ret) > + return ret; > + > + return nvgrace_gpu_read_mem(buf, count, ppos, nvdev); > + } > + > + if (is_fake_bar_pcicfg_emu_reg_access(*ppos)) > + return pcibar_read_emu(nvdev, buf, count, ppos); > + So in the VM, if I iterate with setpci to read the BAR using byte, word, or double word, I get different results. At the BAR2/3 base I get -EINVAL unless it's a 4-byte access, otherwise I fall through below and see values from the real BAR that are inconsistent with the VM devices view. Please implement for all naturally aligned offsets and widths or find a spec statement supporting this behavior. > + return vfio_pci_core_read(core_vdev, buf, count, ppos); > +} > + > +/* > + * Write count bytes to the device memory at a given offset. The actual device > + * memory size (available) may not be a power-of-2. So the driver fakes the > + * size to a power-of-2 (reported) when exposing to a user space driver. > + * > + * Write request beyond the actual device size are dropped, while those > + * beyond the actual reported size are skipped entirely. > + * > + * A write to a negative or an offset greater than the reported size, a > + * negative count are considered error conditions and returned with an -EINVAL. > + */ > +static ssize_t > +nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf, > + struct nvgrace_gpu_vfio_pci_core_device *nvdev) > +{ > + u64 offset = *ppos & VFIO_PCI_OFFSET_MASK; > + size_t mem_count, bar_size = roundup_pow_of_two(nvdev->memlength); > + > + if (offset >= bar_size) > + return -EINVAL; > + > + /* Clip short the write request beyond reported BAR size */ > + count = min(count, bar_size - (size_t)offset); > + > + /* > + * Determine how many bytes to be actually written to the device memory. > + * Do not write to the offset beyond available size. > + */ > + if (offset >= nvdev->memlength) > + goto exitfn; > + > + mem_count = min(count, nvdev->memlength - (size_t)offset); > + > + /* > + * Only the device memory present on the hardware is mapped, which may > + * not be power-of-2 aligned. A write to the BAR2 region implies an > + * access outside the available device memory on the hardware. Drop > + * those write requests. > + */ > + if (copy_from_user((u8 *)nvdev->memmap + offset, buf, mem_count)) > + return -EFAULT; > + > +exitfn: > + *ppos += count; > + return count; > +} > + > +static ssize_t pcibar_write_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev, > + const char __user *buf, size_t count, loff_t *ppos) > +{ > + u64 pos = *ppos & VFIO_PCI_OFFSET_MASK; > + u64 size; > + u32 val; > + > + if (!IS_ALIGNED(pos, 4) || !(is_fake_bar_pcicfg_emu_reg_access(*ppos))) > + return -EINVAL; > + > + if (copy_from_user(&val, buf, count)) > + return -EFAULT; > + > + size = ~(roundup_pow_of_two(nvdev->memlength) - 1); > + > + if (val == 0xffffffff) { > + switch (pos) { > + case PCI_BASE_ADDRESS_2: > + nvdev->bar_regs[0] = (size & GENMASK(31, 4)) | > + (nvdev->bar_regs[0] & GENMASK(3, 0)); > + break; > + case PCI_BASE_ADDRESS_3: > + nvdev->bar_regs[1] = size >> 32; > + break; > + } > + } else { > + switch (pos) { > + case PCI_BASE_ADDRESS_2: > + nvdev->bar_regs[0] = val; > + break; > + case PCI_BASE_ADDRESS_3: > + nvdev->bar_regs[1] = val; > + break; > + } > + } I'd suggest your bar_regs should be a union including a u64 and prior to any read you do something like: bar_reg &= ~(size - 1); bar_reg |= PCI_BASE_ADDRESS_MEM_TYPE_64 | PCI_BASE_ADDRESS_MEM_PREFETCH; Then you don't need to do anything on write. Also note that config sizing doesn't require writing the lower bits, they're defined as read-only. This algorithm would also allow you to just zero the u64 field on init/reset and memcpy any naturally aligned buffer requested by the user. But also note that config space is defined as little endian, so the buffer should be declared as __le64 and each line above should be wrapped in cpu_to_le64(). Bad precedent otherwise even if this will never run on a big endian host. Thanks, Alex > + > + *ppos += count; > + return count; > +} > + > +static ssize_t nvgrace_gpu_vfio_pci_write(struct vfio_device *core_vdev, > + const char __user *buf, size_t count, loff_t *ppos) > +{ > + unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos); > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of( > + core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev); > + int ret; > + > + if (index == VFIO_PCI_BAR2_REGION_INDEX) { > + ret = nvgrace_gpu_memmap(nvdev); > + if (ret) > + return ret; > + > + return nvgrace_gpu_write_mem(count, ppos, buf, nvdev); > + } > + > + if (is_fake_bar_pcicfg_emu_reg_access(*ppos)) > + return pcibar_write_emu(nvdev, buf, count, ppos); > + > + return vfio_pci_core_write(core_vdev, buf, count, ppos); > +} > + > +static const struct vfio_device_ops nvgrace_gpu_vfio_pci_ops = { > + .name = "nvgrace-gpu-vfio-pci", > + .init = vfio_pci_core_init_dev, > + .release = vfio_pci_core_release_dev, > + .open_device = nvgrace_gpu_vfio_pci_open_device, > + .close_device = nvgrace_gpu_vfio_pci_close_device, > + .ioctl = nvgrace_gpu_vfio_pci_ioctl, > + .read = nvgrace_gpu_vfio_pci_read, > + .write = nvgrace_gpu_vfio_pci_write, > + .mmap = nvgrace_gpu_vfio_pci_mmap, > + .request = vfio_pci_core_request, > + .match = vfio_pci_core_match, > + .bind_iommufd = vfio_iommufd_physical_bind, > + .unbind_iommufd = vfio_iommufd_physical_unbind, > + .attach_ioas = vfio_iommufd_physical_attach_ioas, > +}; > + > +static struct > +nvgrace_gpu_vfio_pci_core_device *nvgrace_gpu_drvdata(struct pci_dev *pdev) > +{ > + struct vfio_pci_core_device *core_device = dev_get_drvdata(&pdev->dev); > + > + return container_of(core_device, struct nvgrace_gpu_vfio_pci_core_device, > + core_device); > +} > + > +static int > +nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev, > + struct nvgrace_gpu_vfio_pci_core_device *nvdev) > +{ > + int ret; > + u64 memphys, memlength; > + > + /* > + * The memory information is present in the system ACPI tables as DSD > + * properties nvidia,gpu-mem-base-pa and nvidia,gpu-mem-size. > + */ > + ret = device_property_read_u64(&pdev->dev, "nvidia,gpu-mem-base-pa", > + &(memphys)); > + if (ret) > + return ret; > + > + if (memphys > type_max(phys_addr_t)) > + return -EOVERFLOW; > + > + nvdev->memphys = memphys; > + > + ret = device_property_read_u64(&pdev->dev, "nvidia,gpu-mem-size", > + &(memlength)); > + if (ret) > + return ret; > + > + if (memlength > type_max(size_t)) > + return -EOVERFLOW; > + > + /* > + * If the C2C link is not up due to an error, the coherent device > + * memory size is returned as 0. Fail in such case. > + */ > + if (memlength == 0) > + return -ENOMEM; > + > + nvdev->memlength = memlength; > + > + return ret; > +} > + > +static int nvgrace_gpu_vfio_pci_probe(struct pci_dev *pdev, > + const struct pci_device_id *id) > +{ > + struct nvgrace_gpu_vfio_pci_core_device *nvdev; > + int ret; > + > + nvdev = vfio_alloc_device(nvgrace_gpu_vfio_pci_core_device, core_device.vdev, > + &pdev->dev, &nvgrace_gpu_vfio_pci_ops); > + if (IS_ERR(nvdev)) > + return PTR_ERR(nvdev); > + > + dev_set_drvdata(&pdev->dev, nvdev); > + > + ret = nvgrace_gpu_vfio_pci_fetch_memory_property(pdev, nvdev); > + if (ret) > + goto out_put_vdev; > + > + ret = vfio_pci_core_register_device(&nvdev->core_device); > + if (ret) > + goto out_put_vdev; > + > + return ret; > + > +out_put_vdev: > + vfio_put_device(&nvdev->core_device.vdev); > + return ret; > +} > + > +static void nvgrace_gpu_vfio_pci_remove(struct pci_dev *pdev) > +{ > + struct nvgrace_gpu_vfio_pci_core_device *nvdev = nvgrace_gpu_drvdata(pdev); > + struct vfio_pci_core_device *vdev = &nvdev->core_device; > + > + vfio_pci_core_unregister_device(vdev); > + vfio_put_device(&vdev->vdev); > +} > + > +static const struct pci_device_id nvgrace_gpu_vfio_pci_table[] = { > + /* GH200 120GB */ > + { PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_NVIDIA, 0x2342) }, > + /* GH200 480GB */ > + { PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_NVIDIA, 0x2345) }, > + {} > +}; > + > +MODULE_DEVICE_TABLE(pci, nvgrace_gpu_vfio_pci_table); > + > +static struct pci_driver nvgrace_gpu_vfio_pci_driver = { > + .name = KBUILD_MODNAME, > + .id_table = nvgrace_gpu_vfio_pci_table, > + .probe = nvgrace_gpu_vfio_pci_probe, > + .remove = nvgrace_gpu_vfio_pci_remove, > + .err_handler = &vfio_pci_core_err_handlers, > + .driver_managed_dma = true, > +}; > + > +module_pci_driver(nvgrace_gpu_vfio_pci_driver); > + > +MODULE_LICENSE("GPL v2"); > +MODULE_AUTHOR("Ankit Agrawal <ankita@xxxxxxxxxx>"); > +MODULE_AUTHOR("Aniket Agashe <aniketa@xxxxxxxxxx>"); > +MODULE_DESCRIPTION( > + "VFIO NVGRACE GPU PF - User Level driver for NVIDIA devices with CPU coherently accessible device memory");
