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Message-ID: <56AFCD09.8000807@redhat.com>
Date: Mon, 1 Feb 2016 13:24:25 -0800
From: Laura Abbott <labbott@...hat.com>
To: Mark Rutland <mark.rutland@....com>,
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
On 02/01/2016 04:29 AM, Mark Rutland wrote:
> 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...
>
Hmmm, I based it off of your arm64-pagetable-rework-20160125 tag and
Ard's patch for vmalloc and set_memory_* . The patches seem to apply
on the for-next/pgtable branch as well so I'm guessing you are missing
Ard's patch.
>> ---
>> 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.
>
Yeah, that was what I was going for. I went for the implication with pgtable_alloc
over adding a bool variable to create_mapping. I'll see if I can put a comment
in somewhere to clarify the intentions.
>> 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.
Sounds fine.
>
> Otherwise, this looks good to me.
>
> Mark.
>
Thanks,
Laura
>>
>> 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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