linux-kernel - [PATCH RFC V2 16/17] [dax|pmem]: Enable stray write protection

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Date:   Fri, 17 Jul 2020 00:20:55 -0700
From:   ira.weiny@...el.com
To:     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>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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
Subject: [PATCH RFC V2 16/17] [dax|pmem]: Enable stray write protection

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

Protecting against stray writes is particularly important for PMEM
because, unlike writes to anonymous memory, writes to PMEM persists
across a reboot.  Thus data corruption could result in permanent loss of
data.  Therefore, there is no option presented to the user.

Enable stray write protection by setting the flag in pgmap which
requests it.  Note if Zone Device Access Protection not be supported
this flag will have no affect.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>
---
 drivers/dax/device.c  | 2 ++
 drivers/nvdimm/pmem.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 4c0af2eb7e19..884f66d73d32 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -430,6 +430,8 @@ int dev_dax_probe(struct device *dev)
 	}
 
 	dev_dax->pgmap.type = MEMORY_DEVICE_DEVDAX;
+	dev_dax->pgmap.flags |= PGMAP_PROT_ENABLED;
+
 	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 46c11a09b813..9416a660eede 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -427,6 +427,8 @@ static int pmem_attach_disk(struct device *dev,
 		return -EBUSY;
 	}
 
+	pmem->pgmap.flags |= PGMAP_PROT_ENABLED;
+
 	q = blk_alloc_queue(pmem_make_request, dev_to_node(dev));
 	if (!q)
 		return -ENOMEM;
-- 
2.28.0.rc0.12.gb6a658bd00c9