Messages in this thread |  | | Date | Mon, 27 Aug 2018 10:09:50 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH] irqchip/gic-v3-its: add allocation max order limitation for lpi_id_bits |
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On Mon, 27 Aug 2018 02:41:04 +0100, Jia He <hejianet@gmail.com> wrote: > > Hi Marc > Thanks for the comments > > On 8/27/2018 3:01 AM, Marc Zyngier Wrote: > > [I'm travelling, so expect some major delays in responding to email] > > > > Hi Jia, > > > > On Sun, 26 Aug 2018 10:00:51 +0100, > > Jia He <hejianet@gmail.com> wrote: > >> > >> There is a WARN_ON when my QDF2400 server boots up (pagesize is 4k) > > > > [snip] > > > >> In its_alloc_lpi_tables, lpi_id_bits is 24, without this patch, > >> its_allocate_prop_table will try to allocate 16M(order 12 if > >> pagesize=4k). Thus it causes the WARN_ON. > > > > Gah! QDF and its 24bit INTIDs... Making life hell for everyone ;-) > > > > Sorry for breaking it. > > np, maybe QDF2400 is a little bit special > > > > >> > >> This patch fixes it by limiting the lpi_id_bits. > >> > >> Signed-off-by: Jia He <jia.he@hxt-semitech.com> > >> --- > >> drivers/irqchip/irq-gic-v3-its.c | 5 ++++- > >> 1 file changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > >> index 316a575..79e6993 100644 > >> --- a/drivers/irqchip/irq-gic-v3-its.c > >> +++ b/drivers/irqchip/irq-gic-v3-its.c > >> @@ -1624,8 +1624,11 @@ static void its_free_prop_table(struct page *prop_page) > >> static int __init its_alloc_lpi_tables(void) > >> { > >> phys_addr_t paddr; > >> + u32 max_bits; /*max order limitation in alloc_page*/ > >> > >> - lpi_id_bits = GICD_TYPER_ID_BITS(gic_rdists->gicd_typer); > >> + max_bits = PAGE_SHIFT + MAX_ORDER - 1; > >> + lpi_id_bits = min_t(u32, max_bits, > >> + GICD_TYPER_ID_BITS(gic_rdists->gicd_typer)); > >> gic_rdists->prop_page = its_allocate_prop_table(GFP_NOWAIT); > >> if (!gic_rdists->prop_page) { > >> pr_err("Failed to allocate PROPBASE\n"); > >> -- > >> 1.8.3.1 > >> > > > > I find it rather odd that we end-up with different interrupt ranges > > depending on the CPU page size. Also, allocating that much memory for > > LPIs is rather pointless, as we actually have a pretty low limit of > > interrupts the system can deal with (see IRQ_BITMAP_BITS, which is > > slightly more than 8k). I've so far seen *one* request to push it up, > > but I doubt that it is a real use case. > > > > Capping lpi_id_bits at 16 (which is what we had before) is plenty, > > will save a some memory, and gives some margin before we need to push > > it up again. > > Do you want me to revert commit fe8e93504 to cap the lpi_id_bits > to no greater than ITS_MAX_LPI_NRBITS(16) instead this patch?
Yes, this is probably the best course of action at this time. When I dropped this, I was mostly thinking of the LPI allocator (which now works with an almost constant memory footprint), and didn't pay enough attention to the property table allocation (which is still a function of the number of LPIs).
Thanks,
M.
-- Jazz is not dead, it just smell funny.
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