Messages in this thread | | | Subject | Re: [PATCH] MIPS: fix pmd_mkinvalid | From | Hongchen Zhang <> | Date | Tue, 12 Jul 2022 20:08:43 +0800 |
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On 2022/7/12 下午7:19, Thomas Bogendoerfer wrote: > On Tue, Jul 12, 2022 at 06:01:08PM +0800, Hongchen Zhang wrote: >> On 2022/7/7 下午7:12, Hongchen Zhang wrote: >>> On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote: >>>> On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote: >>>>> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should >>>>> return true. >>>>> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is >>>>> present but invalidated by pmd_mkinvalid. >>>> >>>> What problem are you trying to fix ? What are the symptoms ? >>>> >>>>> Reported-by: kernel test robot <lkp@intel.com> >>>> >>>> the test robot showed problems with your last version of the patch, >>>> which hasn't been integrated into at least the MIPS tree, so no >>>> need to that. >>>> >>>> Thomas. >>>> >>> >>> Hi Thomas, >>> The idea come from the commit: >>> b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM >>> semantics). >>> There is an problem now: >>> CPU 0 CPU 1 >>> pmdp_invalidate do_page_fault >>> ... __handle_mm_fault >>> is_swap_pmd == true >>> trigger VM_BUG_ON() ? >>> set_pmd_at >>> the reason is that pmd_present return true,after this commit >>> pmd_present will return false,and the VM_BUG_ON will not be triggered. >>> Like arm64 does,we can introduce a new bit to fix this. >>> >>> Thanks. >> Hi Thomas, >> Is there problem of this patch? What's your opinion of this patch? > > I haven't dig deeper into it, but needing more page bits is a pain > for 32bit kernel and would make it nearly impossible to get huge > page support there. And the description you gave me, needs to be > in the commit description. > > Thomas. > Hi Thomas, Thanks for your patiently review. For your question, 1. I think there may be problem when compile 32bit kernel with huge page support,because _PAGE_HUGE_SHIFT is only defined for R4K now. 2. I will modify the commit as you said and make a v2 patch.
Thanks. Hongchen Zhang
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