KVM_SET_USER_MEMORY_REGION will fail if the guest physical address is not aligned to the page size. However, it is legal for a guest to program an address which isn't aligned to the page size. Trap and emulate MMIO accesses to the region when that happens. Without this patch, when assigning a Seagate Barracude hard drive to a VM I was seeing these errors: [ 0.286029] pci 0000:00:00.0: BAR 0: assigned [mem 0x41004600-0x4100467f] Error: 0000:01:00.0: failed to register region with KVM Error: [1095:3132] Error activating emulation for BAR 0 [..] [ 10.561794] irq 13: nobody cared (try booting with the "irqpoll" option) [ 10.563122] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-seattle-00009-g909b20467ed1 #133 [ 10.563124] Hardware name: linux,dummy-virt (DT) [ 10.563126] Call trace: [ 10.563134] dump_backtrace+0x0/0x140 [ 10.563137] show_stack+0x14/0x20 [ 10.563141] dump_stack+0xbc/0x100 [ 10.563146] __report_bad_irq+0x48/0xd4 [ 10.563148] note_interrupt+0x288/0x378 [ 10.563151] handle_irq_event_percpu+0x80/0x88 [ 10.563153] handle_irq_event+0x44/0xc8 [ 10.563155] handle_fasteoi_irq+0xb4/0x160 [ 10.563157] generic_handle_irq+0x24/0x38 [ 10.563159] __handle_domain_irq+0x60/0xb8 [ 10.563162] gic_handle_irq+0x50/0xa0 [ 10.563164] el1_irq+0xb8/0x180 [ 10.563166] arch_cpu_idle+0x10/0x18 [ 10.563170] do_idle+0x204/0x290 [ 10.563172] cpu_startup_entry+0x20/0x40 [ 10.563175] rest_init+0xd4/0xe0 [ 10.563180] arch_call_rest_init+0xc/0x14 [ 10.563182] start_kernel+0x420/0x44c [ 10.563183] handlers: [ 10.563650] [<000000001e474803>] sil24_interrupt [ 10.564559] Disabling IRQ #13 [..] [ 11.832916] ata1: spurious interrupt (slot_stat 0x0 active_tag -84148995 sactive 0x0) [ 12.045444] ata_ratelimit: 1 callbacks suppressed With this patch, I don't see the errors and the device works as expected. Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx> --- vfio/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/vfio/core.c b/vfio/core.c index 6b9b58ea8d2f..b23e77c54771 100644 --- a/vfio/core.c +++ b/vfio/core.c @@ -226,6 +226,15 @@ int vfio_map_region(struct kvm *kvm, struct vfio_device *vdev, if (!(region->info.flags & VFIO_REGION_INFO_FLAG_MMAP)) return vfio_setup_trap_region(kvm, vdev, region); + /* + * KVM_SET_USER_MEMORY_REGION will fail because the guest physical + * address isn't page aligned, let's emulate the region ourselves. + */ + if (region->guest_phys_addr & (PAGE_SIZE - 1)) + return kvm__register_mmio(kvm, region->guest_phys_addr, + region->info.size, false, + vfio_mmio_access, region); + if (region->info.flags & VFIO_REGION_INFO_FLAG_READ) prot |= PROT_READ; if (region->info.flags & VFIO_REGION_INFO_FLAG_WRITE) -- 2.20.1
