From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: benh@kernel.crashing.org, mpe@ellerman.id.au,
linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org
Subject: Re: [PATCH V2 08/29] mm: Some arch may want to use HPAGE_PMD related values as variables
Date: Tue, 16 Feb 2016 13:42:42 +0530 [thread overview]
Message-ID: <874md9f4zp.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160215041153.GC3797@oak.ozlabs.ibm.com>
Paul Mackerras <paulus@ozlabs.org> writes:
> On Mon, Feb 08, 2016 at 02:50:20PM +0530, Aneesh Kumar K.V wrote:
>> With next generation power processor, we are having a new mmu model
>> [1] that require us to maintain a different linux page table format.
>>
>> Inorder to support both current and future ppc64 systems with a single
>> kernel we need to make sure kernel can select between different page
>> table format at runtime. With the new MMU (radix MMU) added, we will
>> have two different pmd hugepage size 16MB for hash model and 2MB for
>> Radix model. Hence make HPAGE_PMD related values as a variable.
>
> But this patch doesn't actually turn any constant into a variable, as
> far as I can see...
This get done in a later patch where we rename PMD_SHIFT to H_PMD_SHIFT.
[PATCH V2 15/29] powerpc/mm: Rename hash specific page table bits (_PAGE* -> H_PAGE*)
>
> Most of what this patch does is to move two tests around:
>
> * The #if HPAGE_PMD_ORDER >= MAX_ORDER test get moved from a generic
> header into all archs except powerpc, and for powerpc it gets turned
> into BUILD_BUG_ON. However, BUILD_BUG_ON only works on things that
> are known at compile time, last time I looked. Doesn't it need to be
> a BUG_ON to prepare for HPAGE_PMD_ORDER being a variable that isn't
> known at compile time?
>
> * The existing BUILD_BUG_ON(HPAGE_PMD_ORDER < 2) gets turned into #if
> for all archs except powerpc, and for powerpc it stays as a
> BUILD_BUG_ON but gets moved to arch code. That doesn't really seem to
> accomplish anything. Once again, doesn't it need to become a BUG_ON?
> If so, could we just make it BUG_ON in the generic code where the
> BUILD_BUG_ON currently is?
The patch actually got updated after feedback from Kirill
Updated patch here. We still want to fail during build for ppc64. So
there is a BUILD_BUG_ON also added
http://article.gmane.org/gmane.linux.kernel/2148538
-aneesh
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next prev parent reply other threads:[~2016-02-16 8:12 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-08 9:20 [PATCH V2 00/29] Book3s abstraction in preparation for new MMU model Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 01/29] powerpc/mm: add _PAGE_HASHPTE similar to 4K hash Aneesh Kumar K.V
2016-02-12 2:49 ` Paul Mackerras
2016-02-13 5:08 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 02/29] powerpc/mm: Split pgtable types to separate header Aneesh Kumar K.V
2016-02-12 2:52 ` Paul Mackerras
2016-02-13 5:12 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 03/29] powerpc/mm: Switch book3s 64 with 64K page size to 4 level page table Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 04/29] powerpc/mm: Copy pgalloc (part 1) Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 05/29] powerpc/mm: Copy pgalloc (part 2) Aneesh Kumar K.V
2016-02-12 3:53 ` Paul Mackerras
2016-02-15 5:25 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 06/29] powerpc/mm: Copy pgalloc (part 3) Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 07/29] mm: Make vm_get_page_prot arch specific Aneesh Kumar K.V
2016-02-15 3:21 ` Paul Mackerras
2016-02-15 4:40 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 08/29] mm: Some arch may want to use HPAGE_PMD related values as variables Aneesh Kumar K.V
2016-02-15 4:11 ` Paul Mackerras
2016-02-16 8:12 ` Aneesh Kumar K.V [this message]
2016-02-08 9:20 ` [PATCH V2 09/29] powerpc/mm: Hugetlbfs is book3s_64 and fsl_book3e (32 or 64) Aneesh Kumar K.V
2016-02-15 5:01 ` Paul Mackerras
2016-02-16 8:20 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 10/29] powerpc/mm: free_hugepd_range split to hash and nonhash Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 11/29] powerpc/mm: Use helper instead of opencoding Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 12/29] powerpc/mm: Move hash64 specific defintions to seperate header Aneesh Kumar K.V
2016-02-15 5:24 ` Paul Mackerras
2016-02-16 8:25 ` Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 13/29] powerpc/mm: Move swap related definition ot hash64 header Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 14/29] powerpc/mm: Move hash page table related functions to pgtable-hash64.c Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 15/29] powerpc/mm: Rename hash specific page table bits (_PAGE* -> H_PAGE*) Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 16/29] powerpc/mm: Use flush_tlb_page in ptep_clear_flush_young Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 17/29] powerpc/mm: THP is only available on hash64 as of now Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 18/29] powerpc/mm: Use generic version of pmdp_clear_flush_young Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 19/29] powerpc/mm: Create a new headers for tlbflush for hash64 Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 20/29] powerpc/mm: Hash linux abstraction for page table accessors Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 21/29] powerpc/mm: Hash linux abstraction for functions in pgtable-hash.c Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 22/29] powerpc/mm: Hash linux abstraction for mmu context handling code Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 23/29] powerpc/mm: Move hash related mmu-*.h headers to book3s/ Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 24/29] powerpc/mm: Hash linux abstractions for early init routines Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 25/29] powerpc/mm: Hash linux abstraction for THP Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 26/29] powerpc/mm: Hash linux abstraction for HugeTLB Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 27/29] powerpc/mm: Hash linux abstraction for page table allocator Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 28/29] powerpc/mm: Hash linux abstraction for tlbflush routines Aneesh Kumar K.V
2016-02-08 9:20 ` [PATCH V2 29/29] powerpc/mm: Hash linux abstraction for pte swap encoding Aneesh Kumar K.V
2016-02-09 13:22 ` [PATCH V2 00/29] Book3s abstraction in preparation for new MMU model Aneesh Kumar K.V
2016-02-23 1:59 ` Scott Wood
2016-02-23 2:17 ` Aneesh Kumar K.V
2016-02-12 4:14 ` Paul Mackerras
2016-02-13 5:15 ` Aneesh Kumar K.V
2016-02-13 8:39 ` Denis Kirjanov
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