[RFC PATCH 14/15] nvdimm/pmem: Stray write protection for pmem->virt_addr

[ira.weiny@intel.com]

From: Ira Weiny <ira.weiny@intel.com>

The pmem driver uses a cached virtual address to access its memory
directly.  Because the nvdimm driver is well aware of the special
protections it has mapped memory with, we call dev_access_[en|dis]able()
around the direct pmem->virt_addr (pmem_addr) usage instead of the
unnecessary overhead of trying to get a page to kmap.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 drivers/nvdimm/pmem.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index d25e66fd942d..46c11a09b813 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -148,7 +148,9 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem,
 	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
 		return BLK_STS_IOERR;
 
+	dev_access_enable();
 	rc = read_pmem(page, page_off, pmem_addr, len);
+	dev_access_disable();
 	flush_dcache_page(page);
 	return rc;
 }
@@ -180,11 +182,13 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
 	 * after clear poison.
 	 */
 	flush_dcache_page(page);
+	dev_access_enable();
 	write_pmem(pmem_addr, page, page_off, len);
 	if (unlikely(bad_pmem)) {
 		rc = pmem_clear_poison(pmem, pmem_off, len);
 		write_pmem(pmem_addr, page, page_off, len);
 	}
+	dev_access_disable();
 
 	return rc;
 }
-- 
2.25.1