* Masayoshi Mizuma ([email protected]) wrote:
> Hello,
Hi Masa,
> I would appreciate if you could help me to resolve following failure.
>
> I tried to use virtio-fs on aarch64 [1], however, qemu [2] failed to boot
> as Operation not permitted.
>
> ---
> # ./virtiofsd -o vhost_user_socket=/tmp/vhostqemu -o source=/tmp/share -o
> cache=none &
>
> # qemu-system-aarch64 -machine virt,accel=kvm,gic-version=3 -cpu host -smp
> 8 ... [3]
>
> UEFI firmware starting.
> kvm_set_phys_mem: error registering slot: Operation not permitted
> ---
>
> >From the ftrace log, the error happened because kvm_set_user_memory_region()
> returned as -1 (EPERM).
>
> ---
> qemu-system-aar-28381 [003] .... 6683.601097: tracing_mark_write:
> kvm_set_user_memory Slot#3 flags=0x0 gpa=0x8000000000 size=0x40000000
> ua=0xfffe0ba00000 ret=-1
> ---
>
> kvm_set_user_memory_region() returned -1 because
> kvm_arch_prepare_memory_region()
> in kernel returned as -EPERM.
Right, yes we know this is a problem on aarch64; for aarch we disable
the DAX mode; if you check out our -dev branches and apply the
following hack to the kernel:
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 3f3c018571ee..60a9724f9c71 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -541,7 +541,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev,
struct virtio_fs *fs)
(u8)VIRTIO_FS_SHMCAP_ID_CACHE);
if (!have_cache) {
dev_err(&vdev->dev, "%s: No cache capability\n", __func__);
- return -ENXIO;
+ return 0;
} else {
dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n",
cache_reg.len, cache_reg.addr);
and start the qemu with:
-device vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs,cache-size=0
it should start up for you.
> ---
> int kvm_arch_prepare_memory_region(struct kvm *kvm,
> struct kvm_memory_slot *memslot,
> const struct kvm_userspace_memory_region
> *mem,
> enum kvm_mr_change change)
> {
> ...
> if (writable && !(vma->vm_flags & VM_WRITE)) {
> ret = -EPERM;
> break;
> }
> ---
>
> Actually, the /proc/PID/maps showed ua=0xfffe0ba00000 didn't have PROT_WRITE.
>
> ---
> ...
> 014b0000-014f0000 rw-p 00000000 00:00 0
> 1c840000-1d470000 rw-p 00000000 00:00 0
> [heap]
> fffe0ba00000-fffe4ba00000 ---p 00000000 00:00 0 <===
> fffe4ba00000-fffe4ba10000 ---p 00000000 00:00 0
> fffe4bc00000-fffe4fc00000 rw-p 00000000 00:00 0
> fffe4fc00000-fffe4fc10000 ---p 00000000 00:00 0
> fffe4fe00000-fffe53e00000 rw-p 00000000 00:00 0
> fffe53e00000-fffe53e10000 ---p 00000000 00:00 0
> ...
> ---
>
> I'm not sure why ua=0xfffe0ba00000 didn't have PROT_WRITE because the memory
> was allocated by qemu_anon_ram_alloc() and it should set PROT_READ |
> PROT_WRITE.
Because we explicitly mprotect it later (and in current versions we
allocate with PROT_NONE) - on x86 this works fine, but aarch doesn't
like it; we've not quite figured the rules why yet.
Dave
>
> ---
> qemu-system-aar-28372 [022] .... 6674.795027: tracing_mark_write:
> qemu_anon_ram_alloc size 1073741824 ptr 0xfffe0ba00000
> ---
>
> qemu boots successfully if I remove "-device
> vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs",
> so I suppose the option is related to the failure...
>
>
> [1]: host kernel is 5.2.0.
> guest kernel is https://github.com/rhvgoyal/linux/, branch:
> virtio-fs-dev-5.1.
>
> [2]: I got the qemu from:
> https://gitlab.com/virtio-fs/qemu.git
>
> [3]: Qemu option is:
>
> $QEMU -machine virt,accel=kvm,gic-version=3 \
> -cpu host \
> -smp 8 \
> -m 4G,maxmem=4G \
> -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
> -numa node,memdev=mem \
> -drive
> file=/usr/share/AAVMF/AAVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \
> -drive file=$VARS,if=pflash,format=raw,unit=1 \
> -chardev socket,id=char0,path=/tmp/vhostqemu \
> -device vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs \
> -nographic \
> -serial mon:stdio \
> --trace events=/tmp/qemu-trace-events \
> -drive if=virtio,file=/var/lib/libvirt/images/guest.qcow2
>
> Thanks,
> Masa
>
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--
Dr. David Alan Gilbert / [email protected] / Manchester, UK
