From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: dev@dpdk.org, Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH] igb_uio: fix mmap failure
Date: Fri, 01 Jul 2016 16:54:13 +0200 [thread overview]
Message-ID: <11034006.JJrSj2UUop@xps13> (raw)
In-Reply-To: <577680BE.60408@intel.com>
2016-07-01 15:39, Ferruh Yigit:
> On 7/1/2016 1:47 PM, Thomas Monjalon wrote:
> >> As a workaround igb_uio can stop reserving PCI memory resources, from
> >> kernel point of view io-memory region looks like idle and mmap works
> >> again.
> >>
> >> With this update device io-memory range is not protected against any
> >> other kernel driver claim ownership on those resources, which shouldn't
> >> be a problem for dpdk usage module.
> >
> > Why it should not be a problem?
>
> request_mem_region() is a way for driver informing the rest of the
> kernel that memory region is used.
> And with CONFIG_IO_STRICT_DEVMEM=y, userspace also prevented to touch
> that ares.
> But for igb_uio, we explicitly want userspace to access that memory range.
>
> > Please could you give an example of what could happen?
>
> Technically device lost a protection of its memory region against any
> other driver, but I am not sure if this is real threat in practical life.
> Also this is same in uio_pci_generic, it doesn't reserve the memory.
OK thanks for the explanations.
So we are not sure how this memory region can be stolen and
we assume it won't.
> > This patch fixes a problem with recent kernels (not mentioned above)
> > which offer the uio_pci_generic alternative.
>
> Will give kernel version information.
>
> > That's why I think we should fix it only if there is absolutely no
> > regression for older kernels.
>
> Totally agreed, that is why I expressed my concern, let this patch hang
> around a little.
It may be valuable to have in 16.07.
I suggest to wait RC3 (mid-July) to integrate it.
We will have a RC4 to test it.
next prev parent reply other threads:[~2016-07-01 14:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-01 10:21 Issue with igb_uio in Fedora 24 Mcnamara, John
2016-07-01 10:53 ` Ferruh Yigit
2016-07-01 11:35 ` [PATCH] igb_uio: fix mmap failure Ferruh Yigit
2016-07-01 12:47 ` Thomas Monjalon
2016-07-01 14:39 ` Ferruh Yigit
2016-07-01 14:54 ` Thomas Monjalon [this message]
2016-07-01 15:07 ` [PATCH v2] igb_uio: fix possible mmap failure for Linux > v4.3 Ferruh Yigit
2016-07-01 15:52 ` De Lara Guarch, Pablo
2016-07-01 15:54 ` Ferruh Yigit
2016-07-01 15:59 ` [PATCH v3] igb_uio: fix possible mmap failure for Linux >= v4.5 Ferruh Yigit
2016-07-05 15:00 ` [PATCH v4] " Ferruh Yigit
2016-07-10 13:58 ` Thomas Monjalon
2016-07-02 0:12 ` Issue with igb_uio in Fedora 24 De Lara Guarch, Pablo
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