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. Thanks, Logan
