> Am 09.12.2019 um 21:43 schrieb Dan Williams <dan.j.williams@xxxxxxxxx>: > > On Mon, Dec 9, 2019 at 12:24 PM Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote: >> >> >> >>> On 2019-12-09 12:23 p.m., David Hildenbrand wrote: >>> On 09.12.19 20:13, Logan Gunthorpe wrote: >>>> devm_memremap_pages() is currently used by the PCI P2PDMA code to create >>>> struct page mappings for IO memory. At present, these mappings are created >>>> with PAGE_KERNEL which implies setting the PAT bits to be WB. However, on >>>> x86, an mtrr register will typically override this and force the cache >>>> type to be UC-. In the case firmware doesn't set this register it is >>>> effectively WB and will typically result in a machine check exception >>>> when it's accessed. >>>> >>>> Other arches are not currently likely to function correctly seeing they >>>> don't have any MTRR registers to fall back on. >>>> >>>> To solve this, add an argument to arch_add_memory() to explicitly >>>> set the pgprot value to a specific value. >>>> >>>> Of the arches that support MEMORY_HOTPLUG: x86_64, s390 and arm64 is a >>>> simple change to pass the pgprot_t down to their respective functions >>>> which set up the page tables. For x86_32, set the page tables explicitly >>>> using _set_memory_prot() (seeing they are already mapped). For sh, reject >>>> anything but PAGE_KERNEL settings -- this should be fine, for now, seeing >>>> sh doesn't support ZONE_DEVICE anyway. >>>> >>>> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> >>>> Cc: David Hildenbrand <david@xxxxxxxxxx> >>>> Cc: Michal Hocko <mhocko@xxxxxxxx> >>>> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> >>>> --- >>>> arch/arm64/mm/mmu.c | 4 ++-- >>>> arch/ia64/mm/init.c | 5 ++++- >>>> arch/powerpc/mm/mem.c | 4 ++-- >>>> arch/s390/mm/init.c | 4 ++-- >>>> arch/sh/mm/init.c | 5 ++++- >>>> arch/x86/mm/init_32.c | 7 ++++++- >>>> arch/x86/mm/init_64.c | 4 ++-- >>>> include/linux/memory_hotplug.h | 2 +- >>>> mm/memory_hotplug.c | 2 +- >>>> mm/memremap.c | 2 +- >>>> 10 files changed, 25 insertions(+), 14 deletions(-) >>>> >>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>>> index 60c929f3683b..48b65272df15 100644 >>>> --- a/arch/arm64/mm/mmu.c >>>> +++ b/arch/arm64/mm/mmu.c >>>> @@ -1050,7 +1050,7 @@ int p4d_free_pud_page(p4d_t *p4d, unsigned long addr) >>>> } >>>> >>>> #ifdef CONFIG_MEMORY_HOTPLUG >>>> -int arch_add_memory(int nid, u64 start, u64 size, >>>> +int arch_add_memory(int nid, u64 start, u64 size, pgprot_t prot, >>>> struct mhp_restrictions *restrictions) >>> >>> Can we fiddle that into "struct mhp_restrictions" instead? >> >> Yes, if that's what people want, it's pretty trivial to do. I chose not >> to do it that way because it doesn't get passed down to add_pages() and >> it's not really a "restriction". If I don't hear any objections, I will >> do that for v2. > > +1 to storing this information alongside the altmap in that structure. > However, I agree struct mhp_restrictions, with the MHP_MEMBLOCK_API > flag now gone, has lost all of its "restrictions". How about dropping > the 'flags' property and renaming the struct to 'struct > mhp_modifiers'? > I‘d prefer that over an arch_add_memory_protected() as suggested by Michal. But if we can change it after adding the memory (as also suggested by Michal), that would also be nice. Cheers!
