From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: dev@dpdk.org, david.marchand@redhat.com, ferruh.yigit@intel.com,
grive@u256.net, alvinx.zhang@intel.com, beilei.xing@intel.com,
jia.guo@intel.com, bruce.richardson@intel.com,
dmitry.kozliuk@gmail.com, navasile@linux.microsoft.com,
dmitrym@microsoft.com, pallavi.kadam@intel.com,
talshn@mellanox.com
Subject: Re: [dpdk-dev] [PATCH] pci: keep API compatibility with mmap values
Date: Mon, 13 Jul 2020 09:56:41 +0100 [thread overview]
Message-ID: <63cf0ddf-3d12-06ab-1fd0-a27a827bea74@intel.com> (raw)
In-Reply-To: <2414408.smBOq31esu@thomas>
On 10-Jul-20 5:17 PM, Thomas Monjalon wrote:
> 10/07/2020 17:39, Burakov, Anatoly:
>> On 10-Jul-20 12:53 PM, Thomas Monjalon wrote:
>>> The function pci_map_resource() returns MAP_FAILED in case of error.
>>> When replacing the call to mmap() by rte_mem_map(),
>>> the error code became NULL, breaking the API.
>>> This function is probably not used outside of DPDK,
>>> but it is still a problem for two reasons:
>>> - the deprecation process was not followed
>>> - the Linux function pci_vfio_mmap_bar() is broken for i40e
>>>
>>> The error code is reverted to the Unix value MAP_FAILED.
>>> Windows needs to define this special value (-1 as in Unix).
>>> After proper deprecation process, the API could be changed again
>>> if really needed.
>>>
>>> Because of the switch from mmap() to rte_mem_map(),
>>> another part of the API was changed: "int additional_flags"
>>> are defined as "additional flags for the mapping range"
>>> without mentioning it was directly used in mmap().
>>> Currently it is directly used in rte_mem_map(),
>>> that's why the values rte_map_flags must be mapped (sic) on the mmap ones
>>> in case of Unix OS.
>>>
>>> These are side effects of a badly defined API using Unix values.
> [...]
>>> /** Additional flags for memory mapping. */
>>> enum rte_map_flags {
>>> +#ifdef RTE_EXEC_ENV_WINDOWS
>>> /** Changes to the mapped memory are visible to other processes. */
>>> RTE_MAP_SHARED = 1 << 0,
>>> /** Mapping is not backed by a regular file. */
>>> @@ -35,6 +37,12 @@ enum rte_map_flags {
>>> * it is not required to do so, thus mapping with this flag may fail.
>>> */
>>> RTE_MAP_FORCE_ADDRESS = 1 << 3
>>> +#else /* map mmap flags because they are exposed in pci_map_resource() API */
>>> + RTE_MAP_SHARED = MAP_SHARED,
>>> + RTE_MAP_ANONYMOUS = MAP_ANONYMOUS,
>>> + RTE_MAP_PRIVATE = MAP_PRIVATE,
>>> + RTE_MAP_FORCE_ADDRESS = MAP_FIXED,
>>> +#endif
>>
>> I'm probably missing something, but why is this needed? Doesn't
>
> Yes you missed reading the commit log :)
> Or maybe it is not written clearly enough. Will try to rephrase.
>
>> rte_mem_map() automatically translate these flags into proper ones?
>> pci_map_resource() will call rte_mem_map(), and that will translate
>> these flags into their Unix equivalents.
>
> The problem is that we have an API which is taking mmap flags as input.
> "int additional_flags" is a parameter of the function,
> and are supposed to be mmap flags. But it is not stated clearly.
> When Windows will use this function, it won't use mmap flags
> but RTE_MAP_*. So we must accept both.
> That's why the best is to make values the same.
>
> In 20.11, we could change the API,
> make clear that only RTE_MAP_* is accepted,
> and remove this workaround.
> Or even better, remove pci_map_resource from the PCI lib,
> and implement it in the PCI bus driver.
>
> pci_map_resource() function is a bad designed API
>
>
Right, this makes it clearer :) Thanks!
--
Thanks,
Anatoly
next prev parent reply other threads:[~2020-07-13 8:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 11:53 Thomas Monjalon
2020-07-10 13:34 ` David Marchand
2020-07-10 15:39 ` Burakov, Anatoly
2020-07-10 16:17 ` Thomas Monjalon
2020-07-13 8:56 ` Burakov, Anatoly [this message]
2020-07-15 8:01 ` David Marchand
2020-07-10 17:10 ` Thomas Monjalon
2020-07-10 18:31 ` Dmitry Kozlyuk
2020-07-10 20:02 ` Thomas Monjalon
2020-07-10 20:40 ` [dpdk-dev] [PATCH v2] " Thomas Monjalon
2020-07-10 21:07 ` Dmitry Kozlyuk
2020-07-11 9:51 ` Thomas Monjalon
2020-07-11 3:27 ` Ma, LihongX
2020-07-11 9:50 ` Thomas Monjalon
2020-07-11 3:18 ` [dpdk-dev] [PATCH] " Ma, LihongX
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=63cf0ddf-3d12-06ab-1fd0-a27a827bea74@intel.com \
--to=anatoly.burakov@intel.com \
--cc=alvinx.zhang@intel.com \
--cc=beilei.xing@intel.com \
--cc=bruce.richardson@intel.com \
--cc=david.marchand@redhat.com \
--cc=dev@dpdk.org \
--cc=dmitry.kozliuk@gmail.com \
--cc=dmitrym@microsoft.com \
--cc=ferruh.yigit@intel.com \
--cc=grive@u256.net \
--cc=jia.guo@intel.com \
--cc=navasile@linux.microsoft.com \
--cc=pallavi.kadam@intel.com \
--cc=talshn@mellanox.com \
--cc=thomas@monjalon.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).