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Message-ID: <59000A2A.7040402@redhat.com>
Date: Wed, 26 Apr 2017 10:47:06 +0800
From: Xunlei Pang <xpang@...hat.com>
To: Yinghai Lu <yinghai@...nel.org>, Xunlei Pang <xlpang@...hat.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Eric Biederman <ebiederm@...ssion.com>,
Dave Young <dyoung@...hat.com>,
the arch/x86 maintainers <x86@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/2] x86/mm/ident_map: Add PUD level 1GB page support
On 04/26/2017 at 03:49 AM, Yinghai Lu wrote:
> On Tue, Apr 25, 2017 at 2:13 AM, Xunlei Pang <xlpang@...hat.com> wrote:
>> The current kernel_ident_mapping_init() creates the identity
>> mapping using 2MB page(PMD level), this patch adds the 1GB
>> page(PUD level) support.
>>
>> This is useful on large machines to save some reserved memory
>> (as paging structures) in the kdump case when kexec setups up
>> identity mappings before booting into the new kernel.
>>
>> We will utilize this new support in the following patch.
>>
>> Signed-off-by: Xunlei Pang <xlpang@...hat.com>
>> ---
>> arch/x86/boot/compressed/pagetable.c | 2 +-
>> arch/x86/include/asm/init.h | 3 ++-
>> arch/x86/kernel/machine_kexec_64.c | 2 +-
>> arch/x86/mm/ident_map.c | 13 ++++++++++++-
>> arch/x86/power/hibernate_64.c | 2 +-
>> 5 files changed, 17 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
>> index 56589d0..1d78f17 100644
>> --- a/arch/x86/boot/compressed/pagetable.c
>> +++ b/arch/x86/boot/compressed/pagetable.c
>> @@ -70,7 +70,7 @@ static void *alloc_pgt_page(void *context)
>> * Due to relocation, pointers must be assigned at run time not build time.
>> */
>> static struct x86_mapping_info mapping_info = {
>> - .pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
>> + .page_flag = __PAGE_KERNEL_LARGE_EXEC,
>> };
>>
>> /* Locates and clears a region for a new top level page table. */
>> diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
>> index 737da62..46eab1a 100644
>> --- a/arch/x86/include/asm/init.h
>> +++ b/arch/x86/include/asm/init.h
>> @@ -4,8 +4,9 @@
>> struct x86_mapping_info {
>> void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
>> void *context; /* context for alloc_pgt_page */
>> - unsigned long pmd_flag; /* page flag for PMD entry */
>> + unsigned long page_flag; /* page flag for PMD or PUD entry */
>> unsigned long offset; /* ident mapping offset */
>> + bool use_pud_page; /* PUD level 1GB page support */
> how about use direct_gbpages instead?
> use_pud_page is confusing.
ok
>
>> };
>>
>> int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
>> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
>> index 085c3b3..1d4f2b0 100644
>> --- a/arch/x86/kernel/machine_kexec_64.c
>> +++ b/arch/x86/kernel/machine_kexec_64.c
>> @@ -113,7 +113,7 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
>> struct x86_mapping_info info = {
>> .alloc_pgt_page = alloc_pgt_page,
>> .context = image,
>> - .pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
>> + .page_flag = __PAGE_KERNEL_LARGE_EXEC,
>> };
>> unsigned long mstart, mend;
>> pgd_t *level4p;
>> diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
>> index 04210a2..0ad0280 100644
>> --- a/arch/x86/mm/ident_map.c
>> +++ b/arch/x86/mm/ident_map.c
>> @@ -13,7 +13,7 @@ static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
>> if (pmd_present(*pmd))
>> continue;
>>
>> - set_pmd(pmd, __pmd((addr - info->offset) | info->pmd_flag));
>> + set_pmd(pmd, __pmd((addr - info->offset) | info->page_flag));
>> }
>> }
>>
>> @@ -30,6 +30,17 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
>> if (next > end)
>> next = end;
>>
>> + if (info->use_pud_page) {
>> + pud_t pudval;
>> +
>> + if (pud_present(*pud))
>> + continue;
>> +
>> + pudval = __pud((addr - info->offset) | info->page_flag);
>> + set_pud(pud, pudval);
> should mask addr with PUD_MASK.
> addr &= PUD_MASK;
> set_pud(pud, __pmd(addr - info->offset) | info->page_flag);
Yes, will update, thanks for the catch.
Regards,
Xunlei
>
>
>> + continue;
>> + }
>> +
>> if (pud_present(*pud)) {
>> pmd = pmd_offset(pud, 0);
>> ident_pmd_init(info, pmd, addr, next);
>> diff --git a/arch/x86/power/hibernate_64.c b/arch/x86/power/hibernate_64.c
>> index 6a61194..a6e21fe 100644
>> --- a/arch/x86/power/hibernate_64.c
>> +++ b/arch/x86/power/hibernate_64.c
>> @@ -104,7 +104,7 @@ static int set_up_temporary_mappings(void)
>> {
>> struct x86_mapping_info info = {
>> .alloc_pgt_page = alloc_pgt_page,
>> - .pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
>> + .page_flag = __PAGE_KERNEL_LARGE_EXEC,
>> .offset = __PAGE_OFFSET,
>> };
>> unsigned long mstart, mend;
>> --
>> 1.8.3.1
>>
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