Re: [Crash-utility] [Patch V2 2/2] sparc64 changes
On 03/25/2016 02:03 PM, David Miller wrote:
From: Dave Kleikamp <dave.kleikamp(a)oracle.com>
Date: Fri, 25 Mar 2016 13:22:30 -0500
> On 03/24/2016 02:22 PM, David Miller wrote:
>> From: Dave Kleikamp <dave.kleikamp(a)oracle.com>
>> Date: Wed, 23 Mar 2016 17:41:08 -0500
>>
>>> + /* Check for a huge/THP page */
>>> + paddr = pmd_is_huge(pte, vaddr, verbose);
>>> + if (paddr)
>>> + goto out;
>> ...
>>> + paddr = pte_to_pa(pte);
>>> + paddr = paddr | (vaddr & ~PAGE_MASK);
>>
>> This handles transparent huge pages installed at the PMD level, but I don't
>> see that it handles huge PTEs properly, which are encoded at the PTE level.
>
> I've been looking at the huge page code again and I'm not sure what I'm
> missing. Isn't there still a huge PTE in the page table for every 8K
> page with the proper physical address bits?
Yes there is a huge PTE encoded every 8K, but I'm wondering about the
address masking et al. you are doing here...
I'm pretty sure it works. In set_huge_pte_at():
for (i = 0; i < (1 << HUGETLB_PAGE_ORDER); i++) {
set_pte_at(mm, addr, ptep, entry);
ptep++;
addr += PAGE_SIZE;
pte_val(entry) += PAGE_SIZE;
}
Each pte correctly addresses an 8K page. The crash code doesn't really
need to know it's part of a huge page.