linux-ext4 - [PATCH RFC PKS/PMEM 57/58] nvdimm/pmem: Stray access protection for pmem->virt

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Date:   Fri,  9 Oct 2020 12:50:32 -0700
From:   ira.weiny@...el.com
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Ira Weiny <ira.weiny@...el.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
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Subject: [PATCH RFC PKS/PMEM 57/58] nvdimm/pmem: Stray access protection for pmem->virt_addr

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

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fab29b514372..e4dc1ae990fc 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(false);
 	rc = read_pmem(page, page_off, pmem_addr, len);
+	dev_access_disable(false);
 	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(false);
 	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(false);
 
 	return rc;
 }
-- 
2.28.0.rc0.12.gb6a658bd00c9