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

XU Liang liang.xu at cinfotech.cn
Wed Nov 5 17:10:24 CET 2014


I have a multiple processes application. When start a secondary process, we got error message "EAL: pci_map_resource(): cannot mmap(11, 0x7ffff7fba000, 0x20000, 0x0): Bad file descriptor (0x7ffff7fb9000)".The secondary process link difference shared libraries, so the address 0x7ffff7fba000 is used.
------------------------------------------------------------------发件人:Burakov, Anatoly <anatoly.burakov at intel.com>发送时间:2014年11月5日(星期三) 23:59收件人:徐亮 <liang.xu at cinfotech.cn>,dev at dpdk.org <dev at dpdk.org>主 题:RE: 答复:[dpdk-dev] [PATCH] eal: map uio resources after hugepages when the	base_virtaddr is configured.



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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 at cinfotech.cn]


Sent: Wednesday, November 5, 2014 3:49 PM

To: Burakov, Anatoly; dev at 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 ?



------------------------------------------------------------------


发件人:Burakov, Anatoly <anatoly.burakov at intel.com>


发送时间:2014年11月5日(星期三)
 23:10


收件人:徐亮 <liang.xu at cinfotech.cn>,dev at dpdk.org
 <dev at 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 at dpdk.org] On Behalf Of lxu

Sent: Wednesday, November 5, 2014 1:25 PM

To: dev at 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(-)



diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c

index 7e62266..bc7ed3a 100644

--- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c

+++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c

@@ -289,6 +289,11 @@ pci_uio_map_resource(struct rte_pci_device *dev)

struct rte_pci_addr *loc = &dev->addr;

struct mapped_pci_resource *uio_res;

struct pci_map *maps;

+ static void * requested_addr = NULL;

+ if (internal_config.base_virtaddr && NULL == requested_addr) {

+ requested_addr = (uint8_t *) internal_config.base_virtaddr 

+ + internal_config.memory;

+ }



dev->intr_handle.fd = -1;

dev->intr_handle.type = RTE_INTR_HANDLE_UNKNOWN; @@ -371,10 +376,12 @@ pci_uio_map_resource(struct rte_pci_device *dev)

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




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