On Wed, Jan 07, 2026 at 02:13:28PM -0800, Alex Mastro wrote:
> @@ -124,20 +127,43 @@ static void vfio_pci_region_get(struct vfio_pci_device
> *device, int index,
> static void vfio_pci_bar_map(struct vfio_pci_device *device, int index)
> {
> struct vfio_pci_bar *bar = &device->bars[index];
> + size_t align, size;
> + void *map_base, *map_align;
> int prot = 0;
>
> VFIO_ASSERT_LT(index, PCI_STD_NUM_BARS);
> VFIO_ASSERT_NULL(bar->vaddr);
> VFIO_ASSERT_TRUE(bar->info.flags & VFIO_REGION_INFO_FLAG_MMAP);
> + VFIO_ASSERT_GT(bar->info.size, 0);
>
> if (bar->info.flags & VFIO_REGION_INFO_FLAG_READ)
> prot |= PROT_READ;
> if (bar->info.flags & VFIO_REGION_INFO_FLAG_WRITE)
> prot |= PROT_WRITE;
>
> - bar->vaddr = mmap(NULL, bar->info.size, prot, MAP_FILE | MAP_SHARED,
> + /*
> + * Align the mmap for more efficient IOMMU mapping.
> + * The largest PUD size supporting huge pfnmap is 1GiB.
> + */
> + size = bar->info.size;
> + align = min_t(u64, 1ULL << __builtin_ctzll(size), SZ_1G);
> +
> + map_base = mmap(NULL, size + align, PROT_NONE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + VFIO_ASSERT_NE(map_base, MAP_FAILED);
> +
> + map_align = (void *)ALIGN((uintptr_t)map_base, align);
> +
> + if (map_align > map_base)
> + munmap(map_base, map_align - map_base);
> + if (align > (size_t)(map_align - map_base))
I realized that this is tautological. Will fix in v2.
> + munmap(map_align + size, align - (map_align - map_base));
> +
> + bar->vaddr = mmap(map_align, size, prot, MAP_SHARED | MAP_FIXED,
> device->fd, bar->info.offset);
> VFIO_ASSERT_NE(bar->vaddr, MAP_FAILED);
> +
> + madvise(bar->vaddr, size, MADV_HUGEPAGE);
> }
