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, provide a way to specify the pgprot value explicitly to
arch_add_memory().

Of the arches that support MEMORY_HOTPLUG: x86_64, and arm64 need 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 ia64, s390 and
sh, reject anything but PAGE_KERNEL settings -- this should be fine,
for now, seeing these architectures don't support ZONE_DEVICE.

A check in __add_pages() is also added to ensure the pgprot parameter was
set for all arches.

Cc: Dan Williams <redacted>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: David Hildenbrand <redacted>
Acked-by: Michal Hocko <mhocko@suse.com>
---
 arch/arm64/mm/mmu.c            | 3 ++-
 arch/ia64/mm/init.c            | 3 +++
 arch/powerpc/mm/mem.c          | 3 ++-
 arch/s390/mm/init.c            | 3 +++
 arch/sh/mm/init.c              | 3 +++
 arch/x86/mm/init_32.c          | 5 +++++
 arch/x86/mm/init_64.c          | 2 +-
 include/linux/memory_hotplug.h | 2 ++
 mm/memory_hotplug.c            | 5 ++++-
 mm/memremap.c                  | 6 +++---
 10 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index ee37bca8aba8..ea3fa844a8a2 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c

@@ -1058,7 +1058,8 @@ int arch_add_memory(int nid, u64 start, u64 size,
                flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;

        __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
-                            size, PAGE_KERNEL, __pgd_pgtable_alloc, flags);
+                            size, params->pgprot, __pgd_pgtable_alloc,
+                            flags);

        memblock_clear_nomap(start, size);

diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 97bbc23ea1e3..d637b4ea3147 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c

@@ -676,6 +676,9 @@ int arch_add_memory(int nid, u64 start, u64 size,
        unsigned long nr_pages = size >> PAGE_SHIFT;
        int ret;

+       if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot))
+               return -EINVAL;
+
        ret = __add_pages(nid, start_pfn, nr_pages, params);
        if (ret)
                printk("%s: Problem encountered in __add_pages() as ret=%d\n",

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 19b1da5d7eca..832412bc7fad 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c

@@ -138,7 +138,8 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
        resize_hpt_for_hotplug(memblock_phys_mem_size());

        start = (unsigned long)__va(start);
-       rc = create_section_mapping(start, start + size, nid, PAGE_KERNEL);
+       rc = create_section_mapping(start, start + size, nid,
+                                   params->pgprot);
        if (rc) {
                pr_warn("Unable to create mapping for hot added memory 0x%llx..0x%llx: %d\n",
                        start, start + size, rc);

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index e9e4a7abd0cc..87b2d024e75a 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c

@@ -277,6 +277,9 @@ int arch_add_memory(int nid, u64 start, u64 size,
        if (WARN_ON_ONCE(params->altmap))
                return -EINVAL;

+       if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot))
+               return -EINVAL;
+
        rc = vmem_add_mapping(start, size);
        if (rc)
                return rc;

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index e5114c053364..b9de2d4fa57e 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c

@@ -412,6 +412,9 @@ int arch_add_memory(int nid, u64 start, u64 size,
        unsigned long nr_pages = size >> PAGE_SHIFT;
        int ret;

+       if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot)
+               return -EINVAL;
+
        /* We only have ZONE_NORMAL, so this is easy.. */
        ret = __add_pages(nid, start_pfn, nr_pages, params);
        if (unlikely(ret))

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index e25a4218e6ff..96d8e4fb1cc8 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c

@@ -858,6 +858,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
 {
        unsigned long start_pfn = start >> PAGE_SHIFT;
        unsigned long nr_pages = size >> PAGE_SHIFT;
+       int ret;
+
+       ret = _set_memory_prot(start, nr_pages, params->pgprot);