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Subject[PATCH v6 13/13] libnvdimm, pmem: Restore page attributes when clearing errors
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Use clear_mce_nospec() to restore WB mode for the kernel linear mapping
of a pmem page that was marked 'HWPoison'. A page with 'HWPoison' set
has also been marked UC in PAT (page attribute table) via
set_mce_nospec() to prevent speculative retrievals of poison.

The 'HWPoison' flag is only cleared when overwriting an entire page.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/nvdimm/pmem.c | 26 ++++++++++++++++++++++++++
drivers/nvdimm/pmem.h | 13 +++++++++++++
2 files changed, 39 insertions(+)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 68940356cad3..bdaaa7ed49fd 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -20,6 +20,7 @@
#include <linux/hdreg.h>
#include <linux/init.h>
#include <linux/platform_device.h>
+#include <linux/set_memory.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/badblocks.h>
@@ -51,6 +52,30 @@ static struct nd_region *to_region(struct pmem_device *pmem)
return to_nd_region(to_dev(pmem)->parent);
}

+static void hwpoison_clear(struct pmem_device *pmem,
+ phys_addr_t phys, unsigned int len)
+{
+ unsigned long pfn_start, pfn_end, pfn;
+
+ /* only pmem in the linear map supports HWPoison */
+ if (is_vmalloc_addr(pmem->virt_addr))
+ return;
+
+ pfn_start = PHYS_PFN(phys);
+ pfn_end = pfn_start + PHYS_PFN(len);
+ for (pfn = pfn_start; pfn < pfn_end; pfn++) {
+ struct page *page = pfn_to_page(pfn);
+
+ /*
+ * Note, no need to hold a get_dev_pagemap() reference
+ * here since we're in the driver I/O path and
+ * outstanding I/O requests pin the dev_pagemap.
+ */
+ if (test_and_clear_pmem_poison(page))
+ clear_mce_nospec(pfn);
+ }
+}
+
static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
phys_addr_t offset, unsigned int len)
{
@@ -65,6 +90,7 @@ static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
if (cleared < len)
rc = BLK_STS_IOERR;
if (cleared > 0 && cleared / 512) {
+ hwpoison_clear(pmem, pmem->phys_addr + offset, cleared);
cleared /= 512;
dev_dbg(dev, "%#llx clear %ld sector%s\n",
(unsigned long long) sector, cleared,
diff --git a/drivers/nvdimm/pmem.h b/drivers/nvdimm/pmem.h
index a64ebc78b5df..59cfe13ea8a8 100644
--- a/drivers/nvdimm/pmem.h
+++ b/drivers/nvdimm/pmem.h
@@ -1,6 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NVDIMM_PMEM_H__
#define __NVDIMM_PMEM_H__
+#include <linux/page-flags.h>
#include <linux/badblocks.h>
#include <linux/types.h>
#include <linux/pfn_t.h>
@@ -27,4 +28,16 @@ struct pmem_device {

long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn);
+
+#ifdef CONFIG_MEMORY_FAILURE
+static inline bool test_and_clear_pmem_poison(struct page *page)
+{
+ return TestClearPageHWPoison(page);
+}
+#else
+static inline bool test_and_clear_pmem_poison(struct page *page)
+{
+ return false;
+}
+#endif
#endif /* __NVDIMM_PMEM_H__ */
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