Bleh... seems like a great effort just to find that out. Isn't it
better to just ask for a page_size arg?
So who computes page_size and how? Don't just punt things to a caller
without really explaining how the caller is supposed to use it
correctly.
I'd imagine that the ULP knows when it registers huge-pages.
OK, I can scan the scatterlist and check it.
It not missing, we have device attribute page_size_cap which is
a bitmask of supported page shifts (if I'm not mistaken).
Hum. That is what it should be..
Some drivers are wrong:
#define C2_MIN_PAGESIZE 1024
drivers/infiniband/hw/amso1100/c2_rnic.c: props->page_size_cap = ~(C2_MIN_PAGESIZE-1);
Many set it to PAGE_SIZE, which seems bonkers:
drivers/infiniband/hw/usnic/usnic_ib_verbs.c: props->page_size_cap = USNIC_UIOM_PAGE_SIZE;
drivers/infiniband/hw/usnic/usnic_uiom.h:#define USNIC_UIOM_PAGE_SIZE (PAGE_SIZE)
drivers/infiniband/hw/ipath/ipath_verbs.c: props->page_size_cap = PAGE_SIZE;
drivers/infiniband/hw/qib/qib_verbs.c: props->page_size_cap = PAGE_SIZE;
mlx5 seems to support only 1 page size, Sagi: I assume that needs fixing?
drivers/infiniband/hw/mlx5/main.c: props->page_size_cap = 1ull << MLX5_CAP_GEN(mdev, log_pg_sz);
Yep, fixing it now.
ocrdma,cxgb4,mlx4,mhtca look pretty good, and support various huge
pages.
It is negotiable. Most drivers don't negotiate it though... srp is
the only one who does it.
Well SRP does this:
drivers/infiniband/ulp/srp/ib_srp.c: mr_page_shift = max(12, ffs(dev_attr->page_size_cap) - 1);
drivers/infiniband/ulp/srp/ib_srp.c: srp_dev->mr_page_size = 1 << mr_page_shift;
So it always uses 4096 on supported IB hardware and no huge page
support is enabled. This seems like the wrong way to use
page_size_cap...
Hopefully moving SRP to your new API will fix that.
I have no plans in attempting the try to find the biggest aligned
page_size that is supported by the device.
I'm only going to check HUGE_PAGE, and if not aligned I'll use
PAGE_SIZE and if that's not aligned - fail.
Sagi.
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