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Message-ID: <20160201122911.GF674@leverpostej>
Date: Mon, 1 Feb 2016 12:29:11 +0000
From: Mark Rutland <mark.rutland@....com>
To: Laura Abbott <labbott@...oraproject.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/3] arm64: Add support for
ARCH_SUPPORTS_DEBUG_PAGEALLOC
Hi,
On Fri, Jan 29, 2016 at 03:46:57PM -0800, Laura Abbott wrote:
>
> ARCH_SUPPORTS_DEBUG_PAGEALLOC provides a hook to map and unmap
> pages for debugging purposes. This requires memory be mapped
> with PAGE_SIZE mappings since breaking down larger mappings
> at runtime will lead to TLB conflicts. Check if debug_pagealloc
> is enabled at runtime and if so, map everyting with PAGE_SIZE
> pages. Implement the functions to actually map/unmap the
> pages at runtime.
>
>
> Signed-off-by: Laura Abbott <labbott@...oraproject.org>
I tried to apply atop of the arm64 for-next/pgtable branch, but git
wasn't very happy about that -- which branch/patches is this based on?
I'm not sure if I'm missing something, have something I shouldn't, or if
my MTA is corrupting patches again...
> ---
> arch/arm64/Kconfig | 3 +++
> arch/arm64/mm/mmu.c | 10 +++++++---
> arch/arm64/mm/pageattr.c | 40 +++++++++++++++++++++++++++++++++-------
> 3 files changed, 43 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 8cc6228..0f33218 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -537,6 +537,9 @@ config HOTPLUG_CPU
> source kernel/Kconfig.preempt
> source kernel/Kconfig.hz
>
> +config ARCH_SUPPORTS_DEBUG_PAGEALLOC
> + def_bool y
> +
> config ARCH_HAS_HOLES_MEMORYMODEL
> def_bool y if SPARSEMEM
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 103ebc0..5abbd30 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -181,7 +181,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> do {
> next = pmd_addr_end(addr, end);
> /* try section mapping first */
> - if (((addr | next | phys) & ~SECTION_MASK) == 0) {
> + if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
> + (!debug_pagealloc_enabled() || !pgtable_alloc)) {
> pmd_t old_pmd =*pmd;
> set_pmd(pmd, __pmd(phys |
> pgprot_val(mk_sect_prot(prot))));
> @@ -208,8 +209,11 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
> }
>
> static inline bool use_1G_block(unsigned long addr, unsigned long next,
> - unsigned long phys)
> + unsigned long phys, phys_addr_t (*pgtable_alloc)(void))
> {
> + if (pgtable_alloc && debug_pagealloc_enabled())
> + return false;
> +
> if (PAGE_SHIFT != 12)
> return false;
>
> @@ -241,7 +245,7 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
> /*
> * For 4K granule only, attempt to put down a 1GB block
> */
> - if (use_1G_block(addr, next, phys)) {
> + if (use_1G_block(addr, next, phys, pgtable_alloc)) {
> pud_t old_pud = *pud;
> set_pud(pud, __pud(phys |
> pgprot_val(mk_sect_prot(prot))));
The checks for pgtable_alloc is to allow create_mapping_noalloc to use
sections regardless, right?
I got a little confused by that initially, but that seems to make sense.
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 1360a02..69a8a7d 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -38,7 +38,8 @@ static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
> }
>
> static int change_memory_common(unsigned long addr, int numpages,
> - pgprot_t set_mask, pgprot_t clear_mask)
> + pgprot_t set_mask, pgprot_t clear_mask,
> + bool ignore_vma_check)
> {
> unsigned long start = addr;
> unsigned long size = PAGE_SIZE*numpages;
> @@ -65,11 +66,14 @@ static int change_memory_common(unsigned long addr, int numpages,
> *
> * So check whether the [addr, addr + size) interval is entirely
> * covered by precisely one VM area that has the VM_ALLOC flag set.
> + *
> + * The one exception to this is is we're forcing everything to be
> + * page mapped with DEBUG_PAGEALLOC
> */
> area = find_vm_area((void *)addr);
> - if (!area ||
> + if (!ignore_vma_check && (!area ||
> end > (unsigned long)area->addr + area->size ||
> - !(area->flags & VM_ALLOC))
> + !(area->flags & VM_ALLOC)))
> return -EINVAL;
Perhaps we could pull out everything but the VMA checks into a static
__change_memory_common. Then we can call that directly in
__kernel_map_pages, and don't need to pass a confusing boolean
parameter.
Otherwise, this looks good to me.
Mark.
>
> data.set_mask = set_mask;
> @@ -86,21 +90,24 @@ int set_memory_ro(unsigned long addr, int numpages)
> {
> return change_memory_common(addr, numpages,
> __pgprot(PTE_RDONLY),
> - __pgprot(PTE_WRITE));
> + __pgprot(PTE_WRITE),
> + false);
> }
>
> int set_memory_rw(unsigned long addr, int numpages)
> {
> return change_memory_common(addr, numpages,
> __pgprot(PTE_WRITE),
> - __pgprot(PTE_RDONLY));
> + __pgprot(PTE_RDONLY),
> + false);
> }
>
> int set_memory_nx(unsigned long addr, int numpages)
> {
> return change_memory_common(addr, numpages,
> __pgprot(PTE_PXN),
> - __pgprot(0));
> + __pgprot(0),
> + false);
> }
> EXPORT_SYMBOL_GPL(set_memory_nx);
>
> @@ -108,6 +115,25 @@ int set_memory_x(unsigned long addr, int numpages)
> {
> return change_memory_common(addr, numpages,
> __pgprot(0),
> - __pgprot(PTE_PXN));
> + __pgprot(PTE_PXN),
> + false);
> }
> EXPORT_SYMBOL_GPL(set_memory_x);
> +
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> +void __kernel_map_pages(struct page *page, int numpages, int enable)
> +{
> + unsigned long addr = (unsigned long) page_address(page);
> +
> + if (enable)
> + change_memory_common(addr, numpages,
> + __pgprot(PTE_VALID),
> + __pgprot(0),
> + true);
> + else
> + change_memory_common(addr, numpages,
> + __pgprot(0),
> + __pgprot(PTE_VALID),
> + true);
> +}
> +#endif
> --
> 2.5.0
>
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