linux-kernel - Re: [PATCH RFC V2 0/6] rxe_map_mr

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Date:   Thu, 9 Nov 2023 15:16:58 +0800
From:   Greg Sword <gregsword0@...il.com>
To:     "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
Cc:     Zhu Yanjun <yanjun.zhu@...ux.dev>,
        "zyjzyj2000@...il.com" <zyjzyj2000@...il.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>, "leon@...nel.org" <leon@...nel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rpearsonhpe@...il.com" <rpearsonhpe@...il.com>,
        "Daisuke Matsuda (Fujitsu)" <matsuda-daisuke@...itsu.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "yi.zhang@...hat.com" <yi.zhang@...hat.com>
Subject: Re: [PATCH RFC V2 0/6] rxe_map_mr_sg() fix cleanup and refactor

On Thu, Nov 9, 2023 at 10:25 AM Zhijian Li (Fujitsu)
<lizhijian@...itsu.com> wrote:
>
>
>
> On 06/11/2023 21:58, Zhu Yanjun wrote:
> > 在 2023/11/6 12:07, Zhijian Li (Fujitsu) 写道:
> >>
> >>
> >> On 03/11/2023 21:00, Zhu Yanjun wrote:
> >>> 在 2023/11/3 17:55, Li Zhijian 写道:
> >>>> I don't collect the Reviewed-by to the patch1-2 this time, since i
> >>>> think we can make it better.
> >>>>
> >>>> Patch1-2: Fix kernel panic[1] and benifit to make srp work again.
> >>>>             Almost nothing change from V1.
> >>>> Patch3-5: cleanups # newly add
> >>>> Patch6: make RXE support PAGE_SIZE aligned mr # newly add, but not fully tested
> >>>>
> >>>> My bad arm64 mechine offten hangs when doing blktests even though i use the
> >>>> default siw driver.
> >>>>
> >>>> - nvme and ULPs(rtrs, iser) always registers 4K mr still don't supported yet.
> >>>
> >>> Zhijian
> >>>
> >>> Please read carefully the whole discussion about this problem. You will find a lot of valuable suggestions, especially suggestions from Jason.
> >>
> >> Okay, i will read it again. If you can tell me which thread, that would be better.
> >>
> >>
> >>>
> >>>   From the whole discussion, it seems that the root cause is very clear.
> >>> We need to fix this prolem. Please do not send this kind of commits again.
> >>>
> >>
> >> Let's think about what's our goal first.
> >>
> >> - 1) Fix the panic[1] and only support PAGE_SIZE MR
> >> - 2) support PAGE_SIZE aligned MR
> >> - 3) support any page_size MR.
> >>
> >> I'm sorry i'm not familiar with the linux MM subsystem. It seem it's safe/correct to access
> >> address/memory across pages start from the return of kmap_loca_page(page).
> >> In other words, 2) is already native supported, right?
> >
> > Yes. Please read the comments from Jason, Leon and Bart. They shared a lot of good advice.
>
> I read the whole discussion again, but I believed i still missed a lost.
>
>
> > From them, we can know the root cause and how to fix this problem.
>
> I don't think i misunderstood the root cause:
> RXE splits memory into PAGE_SIZE units in the xarray. As a result, when we extract an address from the xarray,
> we should not access address beyond a PAGE_SIZE window.
>
> IIUC, then how to fix it?
> - I'm not going to "removing page_size set", it's out of this patch scope.
>    Feel free to do the cleanup separately.
> - I'm not going to fix the NVMe/rtrs etc problems in this patch set when 64K page is enabled.
>    But RXE will tell its callers explicitly "RXE don't don't support such page_size"
> - I didn't state RXE supports PAGE_SIZE aligned page_size MR before refactoring rxe_map_mr_sg(),
>    because I worry about it was not correct to access address beyond the PAGE_SIZE window.
>
> What I should do next?
> Just state "RXE support PAGE_SIZE aligned MR" ? Then patches become
> RDMA/rxe: RDMA/rxe: don't allow registering !PAGE_SIZE aligned MR
> RDMA/rxe: set RXE_PAGE_SIZE_CAP to starting from PAGE_SIZE
>

What do you take rdma maillist for? Your bugzilla, jira? or your dev
program launch? Or your play ground?

> Or just keep we have done in the V1
>
> Thanks
>
>
> >
> > Good Luck.
> >
> > Zhu Yanjun
> >
> >>
> >> I get totally confused now.
> >>
> >>
> >>
> >>> Zhu Yanjun
> >>>
> >>>>
> >>>> [1] https://lore.kernel.org/all/CAHj4cs9XRqE25jyVw9rj9YugffLn5+f=1znaBEnu1usLOciD+g@mail.gmail.com/T/
> >>>>
> >>>> Li Zhijian (6):
> >>>>     RDMA/rxe: RDMA/rxe: don't allow registering !PAGE_SIZE mr
> >>>>     RDMA/rxe: set RXE_PAGE_SIZE_CAP to PAGE_SIZE
> >>>>     RDMA/rxe: remove unused rxe_mr.page_shift
> >>>>     RDMA/rxe: Use PAGE_SIZE and PAGE_SHIFT to extract address from
> >>>>       page_list
> >>>>     RDMA/rxe: cleanup rxe_mr.{page_size,page_shift}
> >>>>     RDMA/rxe: Support PAGE_SIZE aligned MR
> >>>>
> >>>>    drivers/infiniband/sw/rxe/rxe_mr.c    | 80 ++++++++++++++++-----------
> >>>>    drivers/infiniband/sw/rxe/rxe_param.h |  2 +-
> >>>>    drivers/infiniband/sw/rxe/rxe_verbs.h |  9 ---
> >>>>    3 files changed, 48 insertions(+), 43 deletions(-)
> >>>>
> >