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Subject[PATCH v4 6/7] mm/memory_hotplug: Add pgprot_t to mhp_params
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.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Dan Williams <dan.j.williams@intel.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 | 12 ++++++++++++
arch/x86/mm/init_64.c | 2 +-
include/linux/memory_hotplug.h | 3 +++
mm/memory_hotplug.c | 5 ++++-
mm/memremap.c | 6 +++---
10 files changed, 36 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..69128f1a22ac 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -858,6 +858,18 @@ 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;
+
+ /*
+ * The page tables were already mapped at boot so if the caller
+ * requests a different mapping type then we must change all the
+ * pages with __set_memory_prot().
+ */
+ if (params->pgprot.pgprot != PAGE_KERNEL.pgprot) {
+ ret = __set_memory_prot(start, nr_pages, params->pgprot);
+ if (ret)
+ return ret;
+ }

return __add_pages(nid, start_pfn, nr_pages, params);
}
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 9e7692080dda..230240af38b4 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -868,7 +868,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;

- init_memory_mapping(start, start + size, PAGE_KERNEL);
+ init_memory_mapping(start, start + size, params->pgprot);

return add_pages(nid, start_pfn, nr_pages, params);
}
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index c5df1b3dada0..3195d11876ea 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -56,9 +56,12 @@ enum {
/*
* Extended parameters for memory hotplug:
* altmap: alternative allocator for memmap array (optional)
+ * pgprot: page protection flags to apply to newly created page tables
+ * (required)
*/
struct mhp_params {
struct vmem_altmap *altmap;
+ pgprot_t pgprot;
};

/*
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c69469e1b40e..d7d4806ad81b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -305,6 +305,9 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
unsigned long nr, start_sec, end_sec;
struct vmem_altmap *altmap = params->altmap;

+ if (WARN_ON_ONCE(!params->pgprot.pgprot))
+ return -EINVAL;
+
err = check_hotplug_memory_addressable(pfn, nr_pages);
if (err)
return err;
@@ -993,7 +996,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
*/
int __ref add_memory_resource(int nid, struct resource *res)
{
- struct mhp_params params = {};
+ struct mhp_params params = { .pgprot = PAGE_KERNEL };
u64 start, size;
bool new_node = false;
int ret;
diff --git a/mm/memremap.c b/mm/memremap.c
index 6891a503a078..06742372a203 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -166,8 +166,8 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
* We do not want any optional features only our own memmap
*/
.altmap = pgmap_altmap(pgmap),
+ .pgprot = PAGE_KERNEL,
};
- pgprot_t pgprot = PAGE_KERNEL;
int error, is_ram;
bool need_devmap_managed = true;

@@ -255,8 +255,8 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
if (nid < 0)
nid = numa_mem_id();

- error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(res->start), 0,
- resource_size(res));
+ error = track_pfn_remap(NULL, &params.pgprot, PHYS_PFN(res->start),
+ 0, resource_size(res));
if (error)
goto err_pfn_remap;

--
2.20.1
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