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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 18:00:01 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

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?

Thanks,

Phil.




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