On Fri, Feb 13, 2015 at 03:49:59PM +0000, Igor Mammedov wrote:
> since commit
> 1d4e7e3 kvm: x86: increase user memory slots to 509
>
> it became possible to use a bigger amount of memory
> slots, which is used by memory hotplug for
> registering hotplugged memory.
> However QEMU aborts if it's used with more than ~60
> pc-dimm devices and vhost-net since host kernel
> in module vhost-net refuses to accept more than 65
> memory regions.
>
> Increasing VHOST_MEMORY_MAX_NREGIONS from 65 to 509
> to match KVM_USER_MEM_SLOTS fixes issue for vhost-net.
>
> Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
This scares me a bit: each region is 32byte, we are talking
a 16K allocation that userspace can trigger.
How does kvm handle this issue?
> ---
> drivers/vhost/vhost.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 2ee2826..ecbd7a4 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -29,7 +29,7 @@
> #include "vhost.h"
>
> enum {
> - VHOST_MEMORY_MAX_NREGIONS = 64,
> + VHOST_MEMORY_MAX_NREGIONS = 509,
> VHOST_MEMORY_F_LOG = 0x1,
> };
>
> --
> 1.8.3.1
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