On Tue, Jul 20, 2010 at 02:42:19PM -0600, Cam Macdonell wrote:
> I think I've found a bug when running a guest with vhost with less
> than 4GB of RAM.
>
> If a guest has less than 4GB of RAM, then above_4g_mem_size is 0 for
> this call to cpu_register_physical_memory() in pc_memory_init() from
> hw/pc.c:922
>
> #if TARGET_PHYS_ADDR_BITS > 32
> cpu_register_physical_memory(0x100000000ULL, above_4g_mem_size,
> ram_addr + below_4g_mem_size);
> #endif
Yes, the fix is in qemu already, it's a matter of merging into qemu-kvm.
> this leads to vhost_client_set_memory being called with size == 0
>
> #3 0x00000000004301f3 in vhost_client_set_memory (client=0x113b010,
> start_addr=4294967296, size=0, phys_offset=3221225472)
> at /home/cam/research/KVM/qemu-kvm/hw/vhost.c:312
>
> which trips the assert at hw/vhost.c:312
>
> static void vhost_client_set_memory(CPUPhysMemoryClient *client,
> target_phys_addr_t start_addr,
> ram_addr_t size,
> ram_addr_t phys_offset)
> {
>
> ...<snip>...
>
> assert(size);
> ...
>
> something like the following fixes the problem but I'm not sure if
> it's the proper way to handle it.
>
> diff --git a/exec.c b/exec.c
> index 5e9a5b7..991abfc 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2592,7 +2592,9 @@ void
> cpu_register_physical_memory_offset(target_phys_addr_t start_addr,
> ram_addr_t orig_size = size;
> subpage_t *subpage;
>
> - cpu_notify_set_memory(start_addr, size, phys_offset);
> + if (size > 0) {
> + cpu_notify_set_memory(start_addr, size, phys_offset);
> + }
>
> if (phys_offset == IO_MEM_UNASSIGNED) {
> region_offset = start_addr;
--
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