From: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
To: "Tan, Jianfeng" <jianfeng.tan@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC] pci: force address of mappings in secondary process
Date: Tue, 11 Jul 2017 12:35:39 +0100 [thread overview]
Message-ID: <3f48cbd3-1e60-5a92-3929-7ba06e3cc69c@intel.com> (raw)
In-Reply-To: <ED26CBA2FAD1BF48A8719AEF02201E365122F647@SHSMSX103.ccr.corp.intel.com>
On 11/07/2017 02:56, Tan, Jianfeng wrote:
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen
>> Hemminger
>> Sent: Tuesday, July 11, 2017 9:13 AM
>> To: dev@dpdk.org
>> Cc: Stephen Hemminger
>> Subject: [dpdk-dev] [RFC] pci: force address of mappings in secondary
>> process
>>
>> The PCI memory resources in the secondary process should be in
>> the exact same location as the primary process. Otherwise
>> there is a risk of a stray pointer.
>>
>> Not sure if this is right, but it looks like a potential
>> problem.
>>
>> ---
>> lib/librte_eal/common/eal_common_pci_uio.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_eal/common/eal_common_pci_uio.c
>> b/lib/librte_eal/common/eal_common_pci_uio.c
>> index 367a6816dcb8..2156b1a436c4 100644
>> --- a/lib/librte_eal/common/eal_common_pci_uio.c
>> +++ b/lib/librte_eal/common/eal_common_pci_uio.c
>> @@ -77,7 +77,7 @@ pci_uio_map_secondary(struct rte_pci_device *dev)
>>
>> void *mapaddr = pci_map_resource(uio_res-
>>> maps[i].addr,
>> fd, (off_t)uio_res->maps[i].offset,
>> - (size_t)uio_res->maps[i].size, 0);
>> + (size_t)uio_res->maps[i].size,
>> MAP_FIXED);
>> /* fd is not needed in slave process, close it */
>> close(fd);
>> if (mapaddr != uio_res->maps[i].addr) {
>> --
>> 2.11.0
> +1 for this RFC. I also once encounter such problem, and I use the same way to solve it. The addr parameter of mmap() syscall is only a hint instead of a must even the VMA is not occupied yet.
>
> Thanks,
> Jianfeng
How do you know the VMA is not occupied?
I think the risk here is that the dynamic linker loaded some shared
library in that VMA, and forcing MAP_FIXED is not a safe solution.
What I have observed is that Linux will return a different VMA than the
one hinted when there is already a mapping in the requested/hinted VMA.
I reckon this is a similar issue as we have with the multi-process model
when we do not get the VMA requested for the huge-pages.
AFAIK we do not have a robust solution for this issue other than restart
the program and hope the dynamic linker does not map anything in the VMA
ranges that we need to map from the primary. This is also assuming that
the application does not allocate memory and maps things before calling
eal_init as it could potentially use VMA ranges that we need in the
secondary process.
The proposal for new secondary process model would solve these issues:
http://dpdk.org/ml/archives/dev/2017-May/066147.html
Thanks,
Sergio
next prev parent reply other threads:[~2017-07-11 11:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-11 1:12 Stephen Hemminger
2017-07-11 1:56 ` Tan, Jianfeng
2017-07-11 11:35 ` Sergio Gonzalez Monroy [this message]
2017-07-11 20:00 ` Stephen Hemminger
2017-07-12 7:24 ` Sergio Gonzalez Monroy
2017-07-12 2:45 ` Tan, Jianfeng
2017-07-12 7:31 ` Sergio Gonzalez Monroy
2017-07-12 8:58 ` Tan, Jianfeng
2019-01-23 19:21 ` Ferruh Yigit
2019-01-23 20:37 ` Stephen Hemminger
2019-01-28 9:59 ` Burakov, Anatoly
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