From: Mike Rapoport <rppt@kernel.org>
To: Vineet Gupta <vgupta@kernel.org>
Cc: linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH 06/18] ARC: mm: Enable STRICT_MM_TYPECHECKS
Date: Wed, 11 Aug 2021 15:04:21 +0300 [thread overview]
Message-ID: <YRO8xUlAtMeJnDbe@kernel.org> (raw)
In-Reply-To: <20210811004258.138075-7-vgupta@kernel.org>
On Tue, Aug 10, 2021 at 05:42:46PM -0700, Vineet Gupta wrote:
> In the past I've refrained from doing this (atleast 2 times) due to the
^ at least
> slight code bloat due to ABI implications of pte_t etc becoming sttuct
^ struct
>
> Per ARC ABI, functions return struct via memory and not through register
> r0, even if the struct would fits in register(s)
^ fit
>
> - caller allocates space on stack and passes the address as first arg
> (r0), shifting rest of args by one
>
> - callee creates return struct in memory (referenced via r0)
>
> This time around the code actually shrunk slightly (due to subtle
> inlining heuristic effects), but still slightly inefficient due to
> return values passed through memory. That however seems like a small
Out of curiosity, is this actually measurable on real world applications?
> cost compared to maintenance burden given the impending new mmu support
> for page walk etc
>
> Signed-off-by: Vineet Gupta <vgupta@kernel.org>
> ---
> arch/arc/include/asm/page.h | 26 --------------------------
> arch/arc/mm/ioremap.c | 2 +-
> 2 files changed, 1 insertion(+), 27 deletions(-)
>
> diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
> index 4a9d33372fe2..c4ac827379cd 100644
> --- a/arch/arc/include/asm/page.h
> +++ b/arch/arc/include/asm/page.h
> @@ -34,12 +34,6 @@ void copy_user_highpage(struct page *to, struct page *from,
> unsigned long u_vaddr, struct vm_area_struct *vma);
> void clear_user_page(void *to, unsigned long u_vaddr, struct page *page);
>
> -#undef STRICT_MM_TYPECHECKS
> -
> -#ifdef STRICT_MM_TYPECHECKS
> -/*
> - * These are used to make use of C type-checking..
> - */
> typedef struct {
> #ifdef CONFIG_ARC_HAS_PAE40
> unsigned long long pte;
> @@ -64,26 +58,6 @@ typedef struct {
>
> #define pte_pgprot(x) __pgprot(pte_val(x))
>
> -#else /* !STRICT_MM_TYPECHECKS */
> -
> -#ifdef CONFIG_ARC_HAS_PAE40
> -typedef unsigned long long pte_t;
> -#else
> -typedef unsigned long pte_t;
> -#endif
> -typedef unsigned long pgd_t;
> -typedef unsigned long pgprot_t;
> -
> -#define pte_val(x) (x)
> -#define pgd_val(x) (x)
> -#define pgprot_val(x) (x)
> -#define __pte(x) (x)
> -#define __pgd(x) (x)
> -#define __pgprot(x) (x)
> -#define pte_pgprot(x) (x)
> -
> -#endif
> -
> typedef pte_t * pgtable_t;
>
> /*
> diff --git a/arch/arc/mm/ioremap.c b/arch/arc/mm/ioremap.c
> index 95c649fbc95a..052bbd8b1e5f 100644
> --- a/arch/arc/mm/ioremap.c
> +++ b/arch/arc/mm/ioremap.c
> @@ -39,7 +39,7 @@ void __iomem *ioremap(phys_addr_t paddr, unsigned long size)
> if (arc_uncached_addr_space(paddr))
> return (void __iomem *)(u32)paddr;
>
> - return ioremap_prot(paddr, size, PAGE_KERNEL_NO_CACHE);
> + return ioremap_prot(paddr, size, pgprot_val(PAGE_KERNEL_NO_CACHE));
> }
> EXPORT_SYMBOL(ioremap);
>
> --
> 2.25.1
>
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2021-08-11 12:04 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 0:42 [PATCH 00/18] ARC mm updates to support 3 or 4 levels of paging Vineet Gupta
2021-08-11 0:42 ` [PATCH 01/18] ARC: mm: simplify mmu scratch register assingment to mmu needs Vineet Gupta
2021-08-11 0:42 ` [PATCH 02/18] ARC: mm: remove tlb paranoid code Vineet Gupta
2021-08-11 0:42 ` [PATCH 03/18] ARC: mm: move mmu/cache externs out to setup.h Vineet Gupta
2021-08-11 5:10 ` Mike Rapoport
2021-08-11 18:46 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 04/18] ARC: mm: remove pgd_offset_fast Vineet Gupta
2021-08-11 5:12 ` Mike Rapoport
2021-08-11 18:54 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 05/18] ARC: mm: Fixes to allow STRICT_MM_TYPECHECKS Vineet Gupta
2021-08-11 0:42 ` [PATCH 06/18] ARC: mm: Enable STRICT_MM_TYPECHECKS Vineet Gupta
2021-08-11 12:04 ` Mike Rapoport [this message]
2021-08-11 19:01 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 07/18] ARC: ioremap: use more commonly used PAGE_KERNEL based uncached flag Vineet Gupta
2021-08-11 5:18 ` Mike Rapoport
2021-08-11 18:58 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 08/18] ARC: mm: pmd_populate* to use the canonical set_pmd (and drop pmd_set) Vineet Gupta
2021-08-11 0:42 ` [PATCH 09/18] ARC: mm: non-functional code cleanup ahead of 3 levels Vineet Gupta
2021-08-11 12:31 ` Mike Rapoport
2021-08-12 1:37 ` Vineet Gupta
2021-08-12 6:18 ` Mike Rapoport
2021-08-12 18:58 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 10/18] ARC: mm: move MMU specific bits out of ASID allocator Vineet Gupta
2021-08-11 0:42 ` [PATCH 11/18] ARC: mm: move MMU specific bits out of entry code Vineet Gupta
2021-08-11 12:15 ` Mike Rapoport
2021-08-11 19:30 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 12/18] ARC: mm: disintegrate mmu.h (arcv2 bits out) Vineet Gupta
2021-08-11 0:42 ` [PATCH 13/18] ARC: mm: disintegrate pgtable.h into levels and flags Vineet Gupta
2021-08-11 0:42 ` [PATCH 14/18] ARC: mm: hack to allow 2 level build with 4 level code Vineet Gupta
2021-08-11 0:42 ` [PATCH 15/18] ARC: mm: support 3 levels of page tables Vineet Gupta
2021-08-11 12:24 ` Mike Rapoport
2021-08-11 22:15 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 16/18] ARC: mm: support 4 " Vineet Gupta
2021-08-11 12:28 ` Mike Rapoport
2021-08-11 22:17 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 17/18] ARC: mm: vmalloc sync from kernel to user table to update PMD Vineet Gupta
2021-08-11 0:42 ` [PATCH 18/18] ARC: mm: introduce _PAGE_TABLE to explicitly link pgd,pud,pmd entries Vineet Gupta
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