From: Maxim Levitsky <mlevitsk@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, Jens Axboe <axboe@fb.com>,
Alex Williamson <alex.williamson@redhat.com>,
Keith Busch <keith.busch@intel.com>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Kirti Wankhede <kwankhede@nvidia.com>,
"David S . Miller" <davem@davemloft.net>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Wolfram Sang <wsa@the-dreams.de>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Liang Cunming <cunming.liang@intel.com>,
Liu Changpeng <changpeng.liu@intel.com>,
Fam Zheng <fam@euphon.net>, Amnon Ilan <ailan@redhat.com>,
John Ferlan <jferlan@redhat.com>
Subject: Re: [PATCH 7/9] nvme/core: add mdev interfaces
Date: Wed, 20 Mar 2019 14:50:04 +0200 [thread overview]
Message-ID: <f55b768e86e77fd9dc36aa7e2602c4f1fd7cd3b1.camel@redhat.com> (raw)
In-Reply-To: <20190320114621.GC5542@stefanha-x1.localdomain>
On Wed, 2019-03-20 at 11:46 +0000, Stefan Hajnoczi wrote:
> On Tue, Mar 19, 2019 at 04:41:14PM +0200, Maxim Levitsky wrote:
> > +int nvme_core_register_mdev_driver(struct nvme_mdev_driver *driver_ops)
> > +{
> > + struct nvme_ctrl *ctrl;
> > +
> > + if (mdev_driver_interface)
> > + return -EEXIST;
> > +
> > + mdev_driver_interface = driver_ops;
>
> Can mdev_driver_interface be accessed from two CPUs at the same time?
> mdev_driver_interface isn't protected by the mutex. The state_changed
> functions below also don't protect mdev_driver_interface.
It can be for sure.
However the only time it is updated is when the mdev core module load/unload
routines.
On module load the interface flips from NULL to a pointer to inside of the
module, so this should be safe, and when mdev module unloads, its reference
counter is 0, and all the callers first try to increase it and fail, they don't
call using this interface.
I might still be wrong with this reasoning though.
Best regards,
Maxim Levitsky
WARNING: multiple messages have this Message-ID (diff)
From: Maxim Levitsky <mlevitsk@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, Jens Axboe <axboe@fb.com>,
Alex Williamson <alex.williamson@redhat.com>,
Keith Busch <keith.busch@intel.com>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Kirti Wankhede <kwankhede@nvidia.com>,
"David S . Miller" <davem@davemloft.net>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Wolfram Sang <wsa@the-dreams.de>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Liang Cunming <cunming.liang@intel.com>,
Liu Changpeng <changpeng.liu@intel.com>,
Fam Zheng <fam@euphon.net>, Amnon Ilan <ailan@redhat.com>,
John Ferlan <jfer
Subject: Re: [PATCH 7/9] nvme/core: add mdev interfaces
Date: Wed, 20 Mar 2019 14:50:04 +0200 [thread overview]
Message-ID: <f55b768e86e77fd9dc36aa7e2602c4f1fd7cd3b1.camel@redhat.com> (raw)
In-Reply-To: <20190320114621.GC5542@stefanha-x1.localdomain>
On Wed, 2019-03-20 at 11:46 +0000, Stefan Hajnoczi wrote:
> On Tue, Mar 19, 2019 at 04:41:14PM +0200, Maxim Levitsky wrote:
> > +int nvme_core_register_mdev_driver(struct nvme_mdev_driver *driver_ops)
> > +{
> > + struct nvme_ctrl *ctrl;
> > +
> > + if (mdev_driver_interface)
> > + return -EEXIST;
> > +
> > + mdev_driver_interface = driver_ops;
>
> Can mdev_driver_interface be accessed from two CPUs at the same time?
> mdev_driver_interface isn't protected by the mutex. The state_changed
> functions below also don't protect mdev_driver_interface.
It can be for sure.
However the only time it is updated is when the mdev core module load/unload
routines.
On module load the interface flips from NULL to a pointer to inside of the
module, so this should be safe, and when mdev module unloads, its reference
counter is 0, and all the callers first try to increase it and fail, they don't
call using this interface.
I might still be wrong with this reasoning though.
Best regards,
Maxim Levitsky
WARNING: multiple messages have this Message-ID (diff)
From: mlevitsk@redhat.com (Maxim Levitsky)
Subject: [PATCH 7/9] nvme/core: add mdev interfaces
Date: Wed, 20 Mar 2019 14:50:04 +0200 [thread overview]
Message-ID: <f55b768e86e77fd9dc36aa7e2602c4f1fd7cd3b1.camel@redhat.com> (raw)
In-Reply-To: <20190320114621.GC5542@stefanha-x1.localdomain>
On Wed, 2019-03-20@11:46 +0000, Stefan Hajnoczi wrote:
> On Tue, Mar 19, 2019@04:41:14PM +0200, Maxim Levitsky wrote:
> > +int nvme_core_register_mdev_driver(struct nvme_mdev_driver *driver_ops)
> > +{
> > + struct nvme_ctrl *ctrl;
> > +
> > + if (mdev_driver_interface)
> > + return -EEXIST;
> > +
> > + mdev_driver_interface = driver_ops;
>
> Can mdev_driver_interface be accessed from two CPUs at the same time?
> mdev_driver_interface isn't protected by the mutex. The state_changed
> functions below also don't protect mdev_driver_interface.
It can be for sure.
However the only time it is updated is when the mdev core module load/unload
routines.
On module load the interface flips from NULL to a pointer to inside of the
module, so this should be safe, and when mdev module unloads, its reference
counter is 0, and all the callers first try to increase it and fail, they don't
call using this interface.
I might still be wrong with this reasoning though.
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2019-03-20 12:50 UTC|newest]
Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 14:41 (unknown) Maxim Levitsky
2019-03-19 14:41 ` No subject Maxim Levitsky
2019-03-19 14:41 ` [PATCH 1/9] vfio/mdev: add .request callback Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 2/9] nvme/core: add some more values from the spec Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 3/9] nvme/core: add NVME_CTRL_SUSPENDED controller state Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 4/9] nvme/pci: use the NVME_CTRL_SUSPENDED state Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-20 2:54 ` Fam Zheng
2019-03-20 2:54 ` Fam Zheng
2019-03-19 14:41 ` [PATCH 5/9] nvme/pci: add known admin effects to augument admin effects log page Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 6/9] nvme/pci: init shadow doorbell after each reset Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 7/9] nvme/core: add mdev interfaces Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-20 11:46 ` Stefan Hajnoczi
2019-03-20 11:46 ` Stefan Hajnoczi
2019-03-20 11:46 ` Stefan Hajnoczi
2019-03-20 12:50 ` Maxim Levitsky [this message]
2019-03-20 12:50 ` Maxim Levitsky
2019-03-20 12:50 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 8/9] nvme/core: add nvme-mdev core driver Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` [PATCH 9/9] nvme/pci: implement the mdev external queue allocation interface Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:41 ` Maxim Levitsky
2019-03-19 14:58 ` [PATCH 0/9] RFC: NVME VFIO mediated device Maxim Levitsky
2019-03-19 14:58 ` Maxim Levitsky
2019-03-25 18:52 ` [PATCH 0/9] RFC: NVME VFIO mediated device [BENCHMARKS] Maxim Levitsky
2019-03-25 18:52 ` Maxim Levitsky
2019-03-26 9:38 ` Stefan Hajnoczi
2019-03-26 9:38 ` Stefan Hajnoczi
2019-03-26 9:38 ` Stefan Hajnoczi
2019-03-26 9:50 ` Maxim Levitsky
2019-03-26 9:50 ` Maxim Levitsky
2019-03-26 9:50 ` Maxim Levitsky
2019-03-19 15:22 ` your mail Keith Busch
2019-03-19 15:22 ` Keith Busch
2019-03-19 15:22 ` Keith Busch
2019-03-19 23:49 ` Chaitanya Kulkarni
2019-03-19 23:49 ` Chaitanya Kulkarni
2019-03-19 23:49 ` Chaitanya Kulkarni
2019-03-20 16:44 ` Maxim Levitsky
2019-03-20 16:44 ` Maxim Levitsky
2019-03-20 16:44 ` Maxim Levitsky
2019-03-20 16:30 ` Maxim Levitsky
2019-03-20 16:30 ` Maxim Levitsky
2019-03-20 16:30 ` Maxim Levitsky
2019-03-20 17:03 ` Keith Busch
2019-03-20 17:03 ` Keith Busch
2019-03-20 17:03 ` Keith Busch
2019-03-20 17:33 ` Maxim Levitsky
2019-03-20 17:33 ` Maxim Levitsky
2019-03-20 17:33 ` Maxim Levitsky
2019-04-08 10:04 ` Maxim Levitsky
2019-04-08 10:04 ` Maxim Levitsky
2019-03-20 11:03 ` Felipe Franciosi
2019-03-20 11:03 ` No subject Felipe Franciosi
2019-03-20 11:03 ` Felipe Franciosi
2019-03-20 19:08 ` Re: Maxim Levitsky
2019-03-20 19:08 ` No subject Maxim Levitsky
2019-03-20 19:08 ` Maxim Levitsky
2019-03-21 16:12 ` Re: Stefan Hajnoczi
2019-03-21 16:12 ` No subject Stefan Hajnoczi
2019-03-21 16:12 ` Stefan Hajnoczi
2019-03-21 16:21 ` Re: Keith Busch
2019-03-21 16:21 ` No subject Keith Busch
2019-03-21 16:21 ` Keith Busch
2019-03-21 16:41 ` Re: Felipe Franciosi
2019-03-21 16:41 ` No subject Felipe Franciosi
2019-03-21 16:41 ` Felipe Franciosi
2019-03-21 17:04 ` Re: Maxim Levitsky
2019-03-21 17:04 ` No subject Maxim Levitsky
2019-03-21 17:04 ` Maxim Levitsky
2019-03-22 7:54 ` Re: Felipe Franciosi
2019-03-22 7:54 ` No subject Felipe Franciosi
2019-03-22 7:54 ` Felipe Franciosi
2019-03-22 10:32 ` Re: Maxim Levitsky
2019-03-22 10:32 ` No subject Maxim Levitsky
2019-03-22 10:32 ` Maxim Levitsky
2019-03-22 15:30 ` Re: Keith Busch
2019-03-22 15:30 ` No subject Keith Busch
2019-03-22 15:30 ` Keith Busch
2019-03-25 15:44 ` Re: Felipe Franciosi
2019-03-25 15:44 ` No subject Felipe Franciosi
2019-03-25 15:44 ` Felipe Franciosi
2019-03-20 15:08 ` [PATCH 0/9] RFC: NVME VFIO mediated device Bart Van Assche
2019-03-20 15:08 ` Bart Van Assche
2019-03-20 16:48 ` Maxim Levitsky
2019-03-20 16:48 ` Maxim Levitsky
2019-03-20 15:28 ` Bart Van Assche
2019-03-20 15:28 ` Bart Van Assche
2019-03-20 16:42 ` Maxim Levitsky
2019-03-20 16:42 ` Maxim Levitsky
2019-03-20 17:03 ` Alex Williamson
2019-03-20 17:03 ` Alex Williamson
2019-03-20 17:03 ` Alex Williamson
2019-03-21 16:13 ` your mail Stefan Hajnoczi
2019-03-21 16:13 ` Stefan Hajnoczi
2019-03-21 16:13 ` Stefan Hajnoczi
2019-03-21 17:07 ` Maxim Levitsky
2019-03-21 17:07 ` Maxim Levitsky
2019-03-21 17:07 ` Maxim Levitsky
2019-03-25 16:46 ` Stefan Hajnoczi
2019-03-25 16:46 ` Stefan Hajnoczi
2019-03-25 16:46 ` Stefan Hajnoczi
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