On Friday, October 13, 2023 9:29 PM Zhu Yanjun:
> 在 2023/10/13 20:01, Daisuke Matsuda (Fujitsu) 写道:
> > On Fri, Oct 13, 2023 10:18 AM Zhu Yanjun wrote:
> >> From: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>
> >>
> >> The page_size of mr is set in infiniband core originally. In the commit
> >> 325a7eb85199 ("RDMA/rxe: Cleanup page variables in rxe_mr.c"), the
> >> page_size is also set. Sometime this will cause conflict.
> >
> > I appreciate your prompt action, but I do not think this commit deals with
> > the root cause. I agree that the problem lies in rxe driver, but what is wrong
> > with assigning actual page size to ibmr.page_size?
>
> Please check the source code. ibmr.page_size is assigned in
> infiniband/core. And then it is assigned in rxe.
> When the 2 are different, the problem will occur.
In the first place, the two must always be equal.
Is there any situation there are two different page sizes for a MR?
I think I have explained the value assigned in the core layer is wrong
when the PAGE_SIZE is bigger than 4k, and that is why they are inconsistent.
As I have no environment to test the kernel panic, it remains speculative,
but I have provided enough information for everyone to rebut my argument.
It is possible I am wrong. I hope someone will tell me specifically where
my guess is wrong, or Yi would kindly take the trouble to verify it.
Thanks,
Daisuke Matsuda
> Please add logs to infiniband/core and rxe to check them.
>
> Zhu Yanjun
>
> >
> > IMO, the problem comes from the device attribute of rxe driver, which is used
> > in ulp/srp layer to calculate the page_size.
> > =====
> > static int srp_add_one(struct ib_device *device)
> > {
> > struct srp_device *srp_dev;
> > struct ib_device_attr *attr = &device->attrs;
> > <...>
> > /*
> > * Use the smallest page size supported by the HCA, down to a
> > * minimum of 4096 bytes. We're unlikely to build large sglists
> > * out of smaller entries.
> > */
> > mr_page_shift = max(12, ffs(attr->page_size_cap) - 1);
> > srp_dev->mr_page_size = 1 << mr_page_shift;
> > =====
> > On initialization of srp driver, mr_page_size is calculated here.
> > Note that the device attribute is used to calculate the value of page shift
> > when the device is trying to use a page size larger than 4096. Since Yi specified
> > CONFIG_ARM64_64K_PAGES, the system naturally met the condition.
> >
> > =====
> > static int srp_map_finish_fr(struct srp_map_state *state,
> > struct srp_request *req,
> > struct srp_rdma_ch *ch, int sg_nents,
> > unsigned int *sg_offset_p)
> > {
> > struct srp_target_port *target = ch->target;
> > struct srp_device *dev = target->srp_host->srp_dev;
> > <...>
> > n = ib_map_mr_sg(desc->mr, state->sg, sg_nents, sg_offset_p,
> > dev->mr_page_size);
> > =====
> > After that, mr_page_size is presumably passed to ib_core layer.
> >
> > =====
> > int ib_map_mr_sg(struct ib_mr *mr, struct scatterlist *sg, int sg_nents,
> > unsigned int *sg_offset, unsigned int page_size)
> > {
> > if (unlikely(!mr->device->ops.map_mr_sg))
> > return -EOPNOTSUPP;
> >
> > mr->page_size = page_size;
> >
> > return mr->device->ops.map_mr_sg(mr, sg, sg_nents, sg_offset);
> > }
> > EXPORT_SYMBOL(ib_map_mr_sg);
> > =====
> > Consequently, the page size calculated in srp driver is set to ibmr.page_size.
> >
> > Coming back to rxe, the device attribute is set here:
> > =====
> > rxe.c
> > <...>
> > /* initialize rxe device parameters */
> > static void rxe_init_device_param(struct rxe_dev *rxe)
> > {
> > rxe->max_inline_data = RXE_MAX_INLINE_DATA;
> >
> > rxe->attr.vendor_id = RXE_VENDOR_ID;
> > rxe->attr.max_mr_size = RXE_MAX_MR_SIZE;
> > rxe->attr.page_size_cap = RXE_PAGE_SIZE_CAP;
> > rxe->attr.max_qp = RXE_MAX_QP;
> > ---
> > rxe_param.h
> > <...>
> > /* default/initial rxe device parameter settings */
> > enum rxe_device_param {
> > RXE_MAX_MR_SIZE = -1ull,
> > RXE_PAGE_SIZE_CAP = 0xfffff000,
> > RXE_MAX_QP_WR = DEFAULT_MAX_VALUE,
> > =====
> > rxe_init_device_param() sets the attributes to rxe_dev->attr, and it is later copied
> > to ib_device->attrs in setup_device()@core/device.c.
> > See that the page size cap is hardcoded to 4096 bytes. I suspect this led to
> > incorrect page_size being set to ibmr.page_size, resulting in the kernel crash.
> >
> > I think rxe driver is made to be able to handle arbitrary page sizes.
> > Probably, we can just modify RXE_PAGE_SIZE_CAP to fix the issue.
> > What do you guys think?
> >
> > Thanks,
> > Daisuke Matsuda
> >
