Re: [Qemu-devel] [PATCH for-2.0] kvm_physical_sync_dirty_bitmap: ignore ENOENT from kvm_vm_ioctl

[Serge Hallyn <serge.hallyn@ubuntu.com>]

Quoting Michael Tokarev (mjt@tls.msk.ru):
> ENOENT means the kernel has an empty dirty bitmap for this
> slot.  Don't abort in that case.  This appears to solve
> the bug reported at
> 
> https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1303926
> 
> which first showed up with commit b533f658a98325d: fix return
> check for KVM_GET_DIRTY_LOG ioctl
> 
> Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

This does look better than my version, thanks.  As you say my version
was closer to the old behavior, but if the kernel has no dirty
bitmap we shouldn't be acting on it, so this looks better imo.

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

(I've not tested yet, but it looks right and works for you :)

> ---
>  kvm-all.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index cd4111d..47fa948 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -441,13 +441,19 @@ static int kvm_physical_sync_dirty_bitmap(MemoryRegionSection *section)
>  
>          d.slot = mem->slot;
>  
> -        if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) < 0) {
> +        ret = kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d);
> +        if (ret >= 0) {
> +            /* regular case, process returned bitmap */
> +            kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
> +        } else if (ret == -ENOENT) {
> +            /* kernel does not have dirty bitmap in this slot */
> +            ret = 0;
> +        } else {
>              DPRINTF("ioctl failed %d\n", errno);
>              ret = -1;
>              break;
>          }
>  
> -        kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
>          start_addr = mem->start_addr + mem->memory_size;
>      }
>      g_free(d.dirty_bitmap);
> -- 
> 1.7.10.4
>