* [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
@ 2017-02-19 10:18 Aneesh Kumar K.V
2017-02-19 21:05 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 5+ messages in thread
From: Aneesh Kumar K.V @ 2017-02-19 10:18 UTC (permalink / raw)
To: benh, paulus, mpe; +Cc: linuxppc-dev, Aneesh Kumar K.V
Without this if firmware reports 1MB page size support we will crash
trying to use 1MB as hugetlb page size.
echo 300 > /sys/kernel/mm/hugepages/hugepages-1024kB/nr_hugepages
kernel BUG at ./arch/powerpc/include/asm/hugetlb.h:19!
.....
....
[c0000000e2c27b30] c00000000029dae8 .hugetlb_fault+0x638/0xda0
[c0000000e2c27c30] c00000000026fb64 .handle_mm_fault+0x844/0x1d70
[c0000000e2c27d70] c00000000004805c .do_page_fault+0x3dc/0x7c0
[c0000000e2c27e30] c00000000000ac98 handle_page_fault+0x10/0x30
With fix, we don't enable 1MB as hugepage size.
bash-4.2# cd /sys/kernel/mm/hugepages/
bash-4.2# ls
hugepages-16384kB hugepages-16777216kB
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
arch/powerpc/mm/hugetlbpage.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 8c3389cbcd12..a4f33de4008e 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -753,6 +753,24 @@ static int __init add_huge_page_size(unsigned long long size)
if ((mmu_psize = shift_to_mmu_psize(shift)) < 0)
return -EINVAL;
+#ifdef CONFIG_PPC_BOOK3S_64
+ /*
+ * We need to make sure that for different page sizes reported by
+ * firmware we only add hugetlb support for page sizes that can be
+ * supported by linux page table layout.
+ * For now we have
+ * Radix: 2M
+ * Hash: 16M and 16G
+ */
+ if (radix_enabled()) {
+ if (mmu_psize != MMU_PAGE_2M)
+ return -EINVAL;
+ } else {
+ if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
+ return -EINVAL;
+ }
+#endif
+
BUG_ON(mmu_psize_defs[mmu_psize].shift != shift);
/* Return if huge page size has already been setup */
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
2017-02-19 10:18 [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout Aneesh Kumar K.V
@ 2017-02-19 21:05 ` Benjamin Herrenschmidt
2017-02-20 3:32 ` Aneesh Kumar K.V
0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Herrenschmidt @ 2017-02-19 21:05 UTC (permalink / raw)
To: Aneesh Kumar K.V, paulus, mpe; +Cc: linuxppc-dev
On Sun, 2017-02-19 at 15:48 +0530, Aneesh Kumar K.V wrote:
> +#ifdef CONFIG_PPC_BOOK3S_64
> + /*
> + * We need to make sure that for different page sizes reported by
> + * firmware we only add hugetlb support for page sizes that can be
> + * supported by linux page table layout.
> + * For now we have
> + * Radix: 2M
> + * Hash: 16M and 16G
> + */
> + if (radix_enabled()) {
> + if (mmu_psize != MMU_PAGE_2M)
> + return -EINVAL;
> + } else {
> + if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
> + return -EINVAL;
> + }
Hash could support others... Same with radix and PUD level pages.
Why do we need that ? Won't FW provide separate properties for hash and
radix page sizes anyway ?
Ben.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
2017-02-19 21:05 ` Benjamin Herrenschmidt
@ 2017-02-20 3:32 ` Aneesh Kumar K.V
2017-02-20 3:35 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 5+ messages in thread
From: Aneesh Kumar K.V @ 2017-02-20 3:32 UTC (permalink / raw)
To: Benjamin Herrenschmidt, paulus, mpe; +Cc: linuxppc-dev
On Monday 20 February 2017 02:35 AM, Benjamin Herrenschmidt wrote:
> On Sun, 2017-02-19 at 15:48 +0530, Aneesh Kumar K.V wrote:
>> +#ifdef CONFIG_PPC_BOOK3S_64
>> + /*
>> + * We need to make sure that for different page sizes reported by
>> + * firmware we only add hugetlb support for page sizes that can be
>> + * supported by linux page table layout.
>> + * For now we have
>> + * Radix: 2M
>> + * Hash: 16M and 16G
>> + */
>> + if (radix_enabled()) {
>> + if (mmu_psize != MMU_PAGE_2M)
>> + return -EINVAL;
>> + } else {
>> + if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
>> + return -EINVAL;
>> + }
> Hash could support others...
On book3s 64 ? I had the above within #ifdef.
> Same with radix and PUD level pages.
Yes, but gigantic hugepage is not yet supported. Once we add that we will
add MMU_PAGE_1G here.
>
> Why do we need that ? Won't FW provide separate properties for hash and
> radix page sizes anyway ?
>
To avoid crashes like the one reported in the commit message due to
buggy firmware ? Also
It can serve as an easy way to understand what hugepage sizes are
supported by different platforms.
I am yet to figure out what the FSL_BOOK3E and PPC_8xx #ifdef above that
hunk is all about. Having
the supported hugepage size clearly verified against makes it easy ?
-aneesh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
2017-02-20 3:32 ` Aneesh Kumar K.V
@ 2017-02-20 3:35 ` Benjamin Herrenschmidt
2017-02-20 5:36 ` Aneesh Kumar K.V
0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Herrenschmidt @ 2017-02-20 3:35 UTC (permalink / raw)
To: Aneesh Kumar K.V, paulus, mpe; +Cc: linuxppc-dev
On Mon, 2017-02-20 at 09:02 +0530, Aneesh Kumar K.V wrote:
> To avoid crashes like the one reported in the commit message due to
> buggy firmware ?
I don't want Linux to make those assumptions. We should fix the FW.
Think of backward compat for example.
> Also
> It can serve as an easy way to understand what hugepage sizes are
> supported by different platforms.
> I am yet to figure out what the FSL_BOOK3E and PPC_8xx #ifdef above
> that
> hunk is all about. Having
> the supported hugepage size clearly verified against makes it easy ?
>
> -aneesh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout
2017-02-20 3:35 ` Benjamin Herrenschmidt
@ 2017-02-20 5:36 ` Aneesh Kumar K.V
0 siblings, 0 replies; 5+ messages in thread
From: Aneesh Kumar K.V @ 2017-02-20 5:36 UTC (permalink / raw)
To: Benjamin Herrenschmidt, paulus, mpe; +Cc: linuxppc-dev
Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> On Mon, 2017-02-20 at 09:02 +0530, Aneesh Kumar K.V wrote:
>> To avoid crashes like the one reported in the commit message due to=C2=A0
>> buggy firmware ?=20
>
> I don't want Linux to make those assumptions. We should fix the FW.
>
I was not suggesting to not fix FW. The idea was two fold.
We cannot support different hugetlb page sizes. They need to
be supported at linux page table level. So a generic check like
is_power_of_2/4() may not be what we want. The second is to document
clearly what are the different page sizes supported by a platform.
-aneesh
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-02-20 5:36 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2017-02-19 10:18 [PATCH] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout Aneesh Kumar K.V
2017-02-19 21:05 ` Benjamin Herrenschmidt
2017-02-20 3:32 ` Aneesh Kumar K.V
2017-02-20 3:35 ` Benjamin Herrenschmidt
2017-02-20 5:36 ` Aneesh Kumar K.V
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