From: Jason Gunthorpe <jgg@ziepe.ca>
To: Steven Price <steven.price@arm.com>
Cc: "Mark Rutland" <Mark.Rutland@arm.com>,
x86@kernel.org, "Arnd Bergmann" <arnd@arndb.de>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Andy Lutomirski" <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"James Morse" <james.morse@arm.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Will Deacon" <will@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org, "Liang,
Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte_hole
Date: Mon, 7 Oct 2019 15:11:13 -0300 [thread overview]
Message-ID: <20191007181113.GC13229@ziepe.ca> (raw)
In-Reply-To: <6e570d6d-b29f-f4cb-1eb9-6ff6cab15a2e@arm.com>
On Mon, Oct 07, 2019 at 05:20:30PM +0100, Steven Price wrote:
> On 07/10/2019 17:10, Jason Gunthorpe wrote:
> > On Mon, Oct 07, 2019 at 04:38:14PM +0100, Steven Price wrote:
> >> diff --git a/mm/hmm.c b/mm/hmm.c
> >> index 902f5fa6bf93..34fe904dd417 100644
> >> +++ b/mm/hmm.c
> >> @@ -376,7 +376,7 @@ static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
> >> }
> >>
> >> static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
> >> - struct mm_walk *walk)
> >> + __always_unused int depth, struct mm_walk *walk)
> >
> > It this __always_unused on function arguments something we are doing
> > now?
>
> $ git grep __always_unused | wc -l
> 191
>
> It's elsewhere in the kernel tree. It seems like a good way of both
> documenting and silencing compiler warnings. But I'm open to other
> suggestions.
The normal kernel build doesn't generate warnings for unused function
parameters because there are alot of false positives, IIRC. So, seems
weird to see things like this.
> > Can we have negative depth? Should it be unsigned?
>
> As per the documentation added in this patch:
>
> * @pte_hole: if set, called for each hole at all levels,
> * depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD
> * 4:PTE. Any folded depths (where PTRS_PER_P?D is equal
> * to 1) are skipped.
>
> So it's signed to allow "-1" in the cases where pte_hole is called
> without knowing the actual depth. This is used in the function
> walk_page_test() because it don't walk the actual page tables, but is
> called on a VMA instead. This means that there may not be a single depth
> for the range provided.
So are the depth values below OK? I would have expected -1 by this
definition
> >> {
> >> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> >> struct hmm_range *range = hmm_vma_walk->range;
> >> @@ -564,7 +564,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> >> again:
> >> pmd = READ_ONCE(*pmdp);
> >> if (pmd_none(pmd))
> >> - return hmm_vma_walk_hole(start, end, walk);
> >> + return hmm_vma_walk_hole(start, end, 0, walk);
> >>
> >> if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
> >> bool fault, write_fault;
> >> @@ -666,7 +666,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> >> again:
> >> pud = READ_ONCE(*pudp);
> >> if (pud_none(pud))
> >> - return hmm_vma_walk_hole(start, end, walk);
> >> + return hmm_vma_walk_hole(start, end, 0, walk);
> >>
> >> if (pud_huge(pud) && pud_devmap(pud)) {
> >> unsigned long i, npages, pfn;
> >> @@ -674,7 +674,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> >> bool fault, write_fault;
> >>
> >> if (!pud_present(pud))
> >> - return hmm_vma_walk_hole(start, end, walk);
> >> + return hmm_vma_walk_hole(start, end, 0, walk);
> >>
> >> i = (addr - range->start) >> PAGE_SHIFT;
> >> npages = (end - addr) >> PAGE_SHIFT;
next prev parent reply other threads:[~2019-10-07 18:11 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 15:38 [PATCH v11 00/22] Generic page walk and ptdump Steven Price
2019-10-07 15:38 ` [PATCH v11 01/22] mm: Add generic p?d_leaf() macros Steven Price
2019-10-07 15:38 ` [PATCH v11 02/22] arc: mm: Add p?d_leaf() definitions Steven Price
2019-10-08 20:19 ` Vineet Gupta
2019-10-07 15:38 ` [PATCH v11 03/22] arm: " Steven Price
2019-10-07 15:38 ` [PATCH v11 04/22] arm64: " Steven Price
2019-10-07 15:38 ` [PATCH v11 05/22] mips: " Steven Price
2019-10-07 15:38 ` [PATCH v11 06/22] powerpc: " Steven Price
2019-10-07 15:38 ` [PATCH v11 07/22] riscv: " Steven Price
2019-10-08 11:31 ` Alex Ghiti
2019-10-08 21:33 ` Paul Walmsley
2019-10-09 10:55 ` Steven Price
2019-10-07 15:38 ` [PATCH v11 08/22] s390: " Steven Price
2019-10-07 15:38 ` [PATCH v11 09/22] sparc: " Steven Price
2019-10-07 15:38 ` [PATCH v11 10/22] x86: " Steven Price
2019-10-07 15:38 ` [PATCH v11 11/22] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-10-07 15:38 ` [PATCH v11 12/22] mm: pagewalk: Allow walking without vma Steven Price
2019-10-07 15:38 ` [PATCH v11 13/22] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-10-07 15:38 ` [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
2019-10-07 16:10 ` Jason Gunthorpe
2019-10-07 16:20 ` Steven Price
2019-10-07 18:11 ` Jason Gunthorpe [this message]
2019-10-09 11:00 ` Steven Price
2019-10-07 15:38 ` [PATCH v11 15/22] x86: mm: Point to struct seq_file from struct pg_state Steven Price
2019-10-07 15:38 ` [PATCH v11 16/22] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-10-07 15:38 ` [PATCH v11 17/22] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-10-07 15:38 ` [PATCH v11 18/22] x86: mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-10-07 15:38 ` [PATCH v11 19/22] mm: Add generic ptdump Steven Price
2019-10-07 15:38 ` [PATCH v11 20/22] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
2019-10-07 15:38 ` [PATCH v11 21/22] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-10-07 15:38 ` [PATCH v11 22/22] arm64: mm: Display non-present entries in ptdump Steven Price
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