On 7/26/23 13:20, David Hildenbrand wrote: > On 26.07.23 08:20, mawupeng wrote: >> >> >> On 2023/7/24 14:11, David Hildenbrand wrote: >>> On 24.07.23 07:54, Anshuman Khandual wrote: >>>> >>>> >>>> On 7/24/23 06:55, mawupeng wrote: >>>>> >>>>> On 2023/7/21 18:36, Will Deacon wrote: >>>>>> On Mon, Jul 17, 2023 at 07:51:50PM +0800, Wupeng Ma wrote: >>>>>>> From: Ma Wupeng <mawupeng1@xxxxxxxxxx> >>>>>>> >>>>>>> During our test, we found that kernel page table may be unexpectedly >>>>>>> cleared with rodata off. The root cause is that the kernel page is >>>>>>> initialized with pud size(1G block mapping) while offline is memory >>>>>>> block size(MIN_MEMORY_BLOCK_SIZE 128M), eg, if 2G memory is hot-added, >>>>>>> when offline a memory block, the call trace is shown below, >>> >>> Is someone adding memory in 2 GiB granularity and then removing parts of it in 128 MiB granularity? That would be against what we support using the add_memory() / offline_and_remove_memory() API and that driver should be fixed instead. >> >> Yes, this kind of situation. >> >> The problem occurs in the following scenarios: >> 1. use mem=xxG to reserve memory. >> 2. add_momory to online memory. >> 3. offline part of the memroy via offline_and_remove_memory. >> >> During my research, ACPI memory removal use memory_subsys_offline to offline memory section and >> this will not delete page table entry which do not trigger this kind of problem. >> >> So I understand what you are talking about. >> 1. 3rd-party driver shouldn't use add_memory/offline_and_remove_memory to online/offline memory. >> If it have to use, this can be achieved by driver. >> 2. memory_subsys_offline is perfered to do such thing. > > No, my point is that > > 1) If you use add_memory() and offline_and_remove_memory() in the *same > granularity* it has to be working, otherwise it has to be fixed. > > 2) If you use add_memory() and offline_and_remove_memory() in different > granularity (especially, add_memory() in bigger granularity) , then > change your code to do add_memory() in the same granularity. > > > If you run into 1), then we populated a PUD for boot memory that also covers yet unpopulated physical memory ranges that are later populated by add_memory(). If that's the case, then we can either fix it by Is that case possible ? __create_pgd_mapping() is called to create the mapping both in hotplug and boot memory cases. alloc_init_pud() ensures [1], that both virtual and physical address ranges are PUD_MASK aligned, before creating a huge or block page entry. (addr | next | phys) & ~PUD_MASK) == 0 > > a) Not doing that. Use PMD tables instead for that piece of memory. > > b) Detecting that that PUD still covers memory and refusing to remove > that PUD. > > c) Rejecting to hotadd memory in this situation at that location. We > have mhp_get_pluggable_range() -> arch_get_mappable_range() to kind- > of handle something like that. >
