From: Jason Gunthorpe <jgg@ziepe.ca>
To: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Alexander Lobakin <aleksander.lobakin@intel.com>,
Souradeep Chakrabarti <schakrabarti@microsoft.com>,
souradeep chakrabarti <schakrabarti@linux.microsoft.com>,
KY Srinivasan <kys@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
Dexuan Cui <decui@microsoft.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"edumazet@google.com" <edumazet@google.com>,
"kuba@kernel.org" <kuba@kernel.org>,
"pabeni@redhat.com" <pabeni@redhat.com>,
Long Li <longli@microsoft.com>,
Ajay Sharma <sharmaajay@microsoft.com>,
"leon@kernel.org" <leon@kernel.org>,
"cai.huoqing@linux.dev" <cai.huoqing@linux.dev>,
"ssengar@linux.microsoft.com" <ssengar@linux.microsoft.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH V4 net] net: mana: Fix MANA VF unload when host is unresponsive
Date: Mon, 10 Jul 2023 15:04:04 -0300 [thread overview]
Message-ID: <ZKxIFK2nQqV9AvIA@ziepe.ca> (raw)
In-Reply-To: <PH7PR21MB311670231963DE8661C2F178CA2CA@PH7PR21MB3116.namprd21.prod.outlook.com>
On Thu, Jul 06, 2023 at 01:54:35PM +0000, Haiyang Zhang wrote:
> > This waiting loop is needed to let the pending Tx packets be sent. If
> > they weren't sent in 1 second, it most likely makes no sense already
> > whether they will be sent at all or not -- the destination host won't
> > wait for them for so long.
> > You say that it may happen only in case of HW issue. If so, I assume you
> > need to fix it some way, e.g. do a HW reset or so? If so, why bother
> > waiting for Tx completions if Tx is hung? You free all skbs later either
> > way, so there are no leaks.
>
> At that point, we don't actually care if the pending packets are sent or not.
> But if we free the queues too soon, and the HW is slow for unexpected
> reasons, a delayed completion notice will DMA into the freed memory and
> cause corruption. That's why we have a longer waiting time.
Aieiiie that is a horrible HW design to not have a strong fence of DMA.
"just wait and hope the HW doesn't UAF the kernel with DMA" is really
awful.
Jason
prev parent reply other threads:[~2023-07-10 18:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 8:49 [PATCH V4 net] net: mana: Fix MANA VF unload when host is unresponsive souradeep chakrabarti
2023-07-03 8:51 ` kernel test robot
2023-07-03 15:51 ` Haiyang Zhang
2023-07-03 16:47 ` Alexander Lobakin
2023-07-03 19:55 ` [EXTERNAL] " Souradeep Chakrabarti
2023-07-04 6:59 ` Paolo Abeni
2023-07-04 13:42 ` Haiyang Zhang
2023-07-05 14:35 ` Alexander Lobakin
2023-07-06 10:41 ` Souradeep Chakrabarti
2023-07-06 11:39 ` Alexander Lobakin
2023-07-06 11:43 ` Souradeep Chakrabarti
2023-07-06 11:48 ` Alexander Lobakin
2023-07-06 13:54 ` Haiyang Zhang
2023-07-10 18:04 ` Jason Gunthorpe [this message]
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