Re: Qemu master crashing on boot when using file backend for memory

[Igor Mammedov]

On Thu, 12 Mar 2020 01:36:48 -0400
Raphael Norwitz <address@hidden> wrote:

> When I try run master qemu I am hitting a divide by zero error. It seems
> to be coming from util/oslib-posix.c in touch_all_pages(). see line 477:
> 
> numpages_per_thread = numpages / memset_num_threads;
> 
> Poking around the crash dumps, I can see that the smp_cpus parameter
> passed in to touch_all_pages() is 0. Going up the stack to
> host_memory_backend_memory_complete() I see backend->prealloc_threads is
> also 0.
> 
> Here’s how I am running qemu
> 
> ./x86_64-softmmu/qemu-system-x86_64 \
>       -kernel /boot/vmlinuz-3.10.0-1062.el7.x86_64  \
>       -netdev user,id=net0,hostfwd=tcp::2250-:22 \
>       -device e1000e,netdev=net0 \
>       -m 1G \
>       -initrd /boot/initramfs-3.10.0-1062.el7.x86_64.img  \
>       -object 
> memory-backend-file,id=ram-node0,prealloc=yes,mem-path=mem,share=yes,size=1G \
>       -numa node,nodeid=0,cpus=0,memdev=ram-node0 
> 
> I don't see this error on a slightly older qemu, as of commit 105b07f1
> (January 27th).
> 
> Interestingly when I remove the memory-backend-file parameter I don’t
> see the error, i.e. this works:
> 
> ./x86_64-softmmu/qemu-system-x86_64 \
>       -kernel /boot/vmlinuz-3.10.0-1062.el7.x86_64  \
>       -netdev user,id=net0,hostfwd=tcp::2250-:22 \
>       -device e1000e,netdev=net0 \
>       -m 1G \
>       -initrd /boot/initramfs-3.10.0-1062.el7.x86_64.img
> 
> Looking at the blame data for backends/hostmem.c I see commit ffac16fa
> introduced some churn in this part of the code. Has anyone else seen
> this issue? Could I be doing something wrong here?

It's know issue, see
 "[PATCH] oslib-posix: initialize mutex and condition variable
for a fix
>