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Fri, 1 May 2020 08:57:14 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E20456A95B; Fri, 1 May 2020 08:57:11 +0000 (UTC) Date: Fri, 1 May 2020 09:57:08 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Igor Mammedov Subject: Re: [PATCH] hostmem: don't use mbind() if host-nodes is epmty Message-ID: <20200501085708.GA2203114@redhat.com> References: <20200430154606.6421-1-imammedo@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200430154606.6421-1-imammedo@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=berrange@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/01 04:28:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: pbonzini@redhat.com, mhohmann@physnet.uni-hamburg.de, qemu-stable@nongnu.org, qemu-devel@nongnu.org, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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) >=20 > 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. >=20 > Reported-by: Manuel Hohmann > Signed-off-by: Igor Mammedov > --- > CC: berrange@redhat.com > CC: ehabkost@redhat.com > CC: pbonzini@redhat.com > CC: mhohmann@physnet.uni-hamburg.de > CC: qemu-stable@nongnu.org > --- > backends/hostmem.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) >=20 > diff --git a/backends/hostmem.c b/backends/hostmem.c > index 327f9eebc3..0efd7b7bd6 100644 > --- a/backends/hostmem.c > +++ b/backends/hostmem.c > @@ -383,8 +383,10 @@ host_memory_backend_memory_complete(UserCreatable *u= c, Error **errp) > assert(sizeof(backend->host_nodes) >=3D > BITS_TO_LONGS(MAX_NODES + 1) * sizeof(unsigned long)); > assert(maxnode <=3D MAX_NODES); > - if (mbind(ptr, sz, backend->policy, > - maxnode ? backend->host_nodes : NULL, maxnode + 1, fla= gs)) { > + > + if (maxnode && > + mbind(ptr, sz, backend->policy, backend->host_nodes, maxnode= + 1, > + flags)) { > if (backend->policy !=3D MPOL_DEFAULT || errno !=3D ENOSYS) = { > error_setg_errno(errp, errno, > "cannot bind memory to host NUMA nodes"= ); personally I would have found this code clearer if the check had been "if (backend->policy !=3D MPOL_DEFAULT && ..." as I had to read quite a few lines to understand that the 'maxnode' is zero if-and-only-if policy =3D=3D MPOL_DEFAULT Regardless though, this is functionally correct so Reviewed-by: Daniel P. Berrang=C3=A9 Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|