[dpdk-dev] 答复： [PATCH] eal: map uio resources after hugepages when the base_virtaddr is configured.

  Hi Liang

Yes it is a problem. Even if it was carefully selected by user, nothing stops the DPDK application from mapping something into where you’re trying to map your UIO devices. Plus, this changes the default behavior where a wrong base-virtaddr leads to a failure to initialize, rather than simply using a different address (remember that pci_map_resource fails if it cannot map the resource at the exact address you requested).

A very crude way of finding out where hugepages end would be to walk the hugepage memory (walk through memsegs and note the maximum start addr + length of that memseg).

Could you perhaps explain what is the problem that you’re trying to solve with this? I can’t think of a situation where the location of UIO maps would matter, to be honest.

Thanks,
Anatoly

From: XU Liang [mailto:liang.xu@cinfotech.cn]

Sent: Wednesday, November 5, 2014 3:49 PM
To: Burakov, Anatoly; dev@dpdk.org
Subject: 答复：[dpdk-dev] [PATCH] eal: map uio resources after hugepages when the base_virtaddr is configured.

I think the base_virtadd will be carefully selected by user when they need it. So maybe it's not a real problem.  :>

The real reason is I can't find a easy way to get the end address of hugepages. Can you give me some suggestions ?
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发件人：Burakov, Anatoly <anatoly.burakov@intel.com<mailto:anatoly.burakov@intel.com>>
发送时间：2014年11月5日(星期三) 23:10
收件人：徐亮 <liang.xu@cinfotech.cn<mailto:liang.xu@cinfotech.cn>>，dev@dpdk.org<mailto:dev@dpdk.org> <dev@dpdk.org<mailto:dev@dpdk.org>>
主　题：RE: [dpdk-dev] [PATCH] eal: map uio resources after hugepages when the base_virtaddr is configured.

I have a slight problems with this patch.

The base_virtaddr doesn't necessarily correspond to an address that everything gets mapped to. It's a "hint" of sorts, that may or may not be taken into account by mmap. Therefore we can't simply assume that if we requested a base-virtaddr, everything will get mapped at exactly that address. We also can't assume that hugepages will be ordered one after the other and occupy neatly all the contiguous virtual memory between base_virtaddr and base_virtaddr + internal_config.memory - there may be holes, for whatever reasons.

Also,

Thanks,
Anatoly

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of lxu

Sent: Wednesday, November 5, 2014 1:25 PM
To: dev@dpdk.org<mailto:dev@dpdk.org>
Subject: [dpdk-dev] [PATCH] eal: map uio resources after hugepages when the base_virtaddr is configured.

---
lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

if (maps[j].addr != NULL)
fail = 1;
else {
- mapaddr = pci_map_resource(NULL, fd, (off_t)offset,
+ mapaddr = pci_map_resource(requested_addr, fd, (off_t)offset,
(size_t)maps[j].size);
if (mapaddr == NULL)
fail = 1;
+ else if (NULL != requested_addr)
+ requested_addr = (uint8_t *)mapaddr + maps[j].size;
}

if (fail) {
--
1.9.1