linux-kernel - Re: [PATCH for-next v8 3/6] RDMA/rxe: Add page invalidation support

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Message-ID: <ebff6ffc-9471-4393-aa8b-bbfe158335ea@linux.dev>
Date: Mon, 28 Oct 2024 21:26:10 +0100
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: "Daisuke Matsuda (Fujitsu)" <matsuda-daisuke@...itsu.com>,
 "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
 "leon@...nel.org" <leon@...nel.org>, "jgg@...pe.ca" <jgg@...pe.ca>,
 "zyjzyj2000@...il.com" <zyjzyj2000@...il.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "rpearsonhpe@...il.com" <rpearsonhpe@...il.com>,
 "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
Subject: Re: [PATCH for-next v8 3/6] RDMA/rxe: Add page invalidation support

在 2024/10/28 8:25, Daisuke Matsuda (Fujitsu) 写道:
> On Sun, Oct 13, 2024 3:16 PM Zhu Yanjun wrote:
>> 在 2024/10/9 9:59, Daisuke Matsuda 写道:
>>> On page invalidation, an MMU notifier callback is invoked to unmap DMA
>>> addresses and update the driver page table(umem_odp->dma_list). It also
>>> sets the corresponding entries in MR xarray to NULL to prevent any access.
>>> The callback is registered when an ODP-enabled MR is created.
>>>
>>> Signed-off-by: Daisuke Matsuda <matsuda-daisuke@...itsu.com>
>>> ---
>>>    drivers/infiniband/sw/rxe/Makefile  |  2 +
>>>    drivers/infiniband/sw/rxe/rxe_odp.c | 57 +++++++++++++++++++++++++++++
>>>    2 files changed, 59 insertions(+)
>>>    create mode 100644 drivers/infiniband/sw/rxe/rxe_odp.c
>>>
>>> diff --git a/drivers/infiniband/sw/rxe/Makefile b/drivers/infiniband/sw/rxe/Makefile
>>> index 5395a581f4bb..93134f1d1d0c 100644
>>> --- a/drivers/infiniband/sw/rxe/Makefile
>>> +++ b/drivers/infiniband/sw/rxe/Makefile
>>> @@ -23,3 +23,5 @@ rdma_rxe-y := \
>>>    	rxe_task.o \
>>>    	rxe_net.o \
>>>    	rxe_hw_counters.o
>>> +
>>> +rdma_rxe-$(CONFIG_INFINIBAND_ON_DEMAND_PAGING) += rxe_odp.o
>>> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
>>> new file mode 100644
>>> index 000000000000..ea55b79be0c6
>>> --- /dev/null
>>> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
>>> @@ -0,0 +1,57 @@
>>> +// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
>>> +/*
>>> + * Copyright (c) 2022-2023 Fujitsu Ltd. All rights reserved.
>>> + */
>>> +
>>> +#include <linux/hmm.h>
>>> +
>>> +#include <rdma/ib_umem_odp.h>
>>> +
>>> +#include "rxe.h"
>>> +
>>> +static void rxe_mr_unset_xarray(struct rxe_mr *mr, unsigned long start,
>>> +				unsigned long end)
>>> +{
>>> +	unsigned long upper = rxe_mr_iova_to_index(mr, end - 1);
>>> +	unsigned long lower = rxe_mr_iova_to_index(mr, start);
>>> +	void *entry;
>>> +
>>> +	XA_STATE(xas, &mr->page_list, lower);
>>> +
>>> +	/* make elements in xarray NULL */
>>> +	xas_lock(&xas);
>>> +	xas_for_each(&xas, entry, upper)
>>> +		xas_store(&xas, NULL);
>>> +	xas_unlock(&xas);
>>> +}
>>> +
>>> +static bool rxe_ib_invalidate_range(struct mmu_interval_notifier *mni,
>>> +				    const struct mmu_notifier_range *range,
>>> +				    unsigned long cur_seq)
>>> +{
>>> +	struct ib_umem_odp *umem_odp =
>>> +		container_of(mni, struct ib_umem_odp, notifier);
>>> +	struct rxe_mr *mr = umem_odp->private;
>>> +	unsigned long start, end;
>>> +
>>> +	if (!mmu_notifier_range_blockable(range))
>>> +		return false;
>>> +
>>> +	mutex_lock(&umem_odp->umem_mutex);
>>
>> guard(mutex)(&umem_odp->umem_mutex);
>>
>> It seems that the above is more popular.
> 
> Thanks for the comment.
> 
> I have no objection to your suggestion since the increasing number of
> kernel components use "guard(mutex)" syntax these days, but I would rather
> suggest making the change to the whole infiniband subsystem at once because
> there are multiple mutex lock/unlock pairs to be converted.

If you want to make the such changes to the whole infiniband subsystem, 
I am fine with it.

The "guard(mutex)" is used in the following patch.

https://patchwork.kernel.org/project/linux-rdma/patch/20241009210048.4122518-1-bvanassche@acm.org/

Zhu Yanjun

> 
> Regards,
> Daisuke Matsuda
> 
>>
>> Zhu Yanjun
>>> +	mmu_interval_set_seq(mni, cur_seq);
>>> +
>>> +	start = max_t(u64, ib_umem_start(umem_odp), range->start);
>>> +	end = min_t(u64, ib_umem_end(umem_odp), range->end);
>>> +
>>> +	rxe_mr_unset_xarray(mr, start, end);
>>> +
>>> +	/* update umem_odp->dma_list */
>>> +	ib_umem_odp_unmap_dma_pages(umem_odp, start, end);
>>> +
>>> +	mutex_unlock(&umem_odp->umem_mutex);
>>> +	return true;
>>> +}
>>> +
>>> +const struct mmu_interval_notifier_ops rxe_mn_ops = {
>>> +	.invalidate = rxe_ib_invalidate_range,
>>> +};
>