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Re: [PATCH] hostmem: don't use mbind() if host-nodes is epmty


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] hostmem: don't use mbind() if host-nodes is epmty
Date: Mon, 11 May 2020 22:03:45 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

On 5/11/20 9:24 PM, Igor Mammedov wrote:
On Mon, 11 May 2020 18:00:01 +0200
Philippe Mathieu-Daudé <address@hidden> wrote:

Hi Eduardo,

On 5/4/20 5:44 PM, Eduardo Habkost wrote:
On Thu, Apr 30, 2020 at 11:46:06AM -0400, Igor Mammedov wrote:
Since 5.0 QEMU uses hostmem backend for allocating main guest RAM.
The backend however calls mbind() which is typically NOP
in case of default policy/absent host-nodes bitmap.
However when runing in container with black-listed mbind()
syscall, QEMU fails to start with error
   "cannot bind memory to host NUMA nodes: Operation not permitted"
even when user hasn't provided host-nodes to pin to explictly
(which is the case with -m option)

To fix issue, call mbind() only in case when user has provided
host-nodes explicitly (i.e. host_nodes bitmap is not empty).
That should allow to run QEMU in containers with black-listed
mbind() without memory pinning. If QEMU provided memory-pinning
is required user still has to white-list mbind() in container
configuration.

Reported-by: Manuel Hohmann <address@hidden>
Signed-off-by: Igor Mammedov <address@hidden>

Queued on machine-next, thanks!

I've been debugging this issue again today and figured it was not
merged, if possible can you add the "Cc: address@hidden" tag
before sending your pull request?
it's CCed already, so my impression was that will should picked up once it was 
reviewed.

Correct, however some distributions find easier to grep for the 'Cc: address@hidden' merged tag before qemu-stable is released.



Thanks,

Phil.






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