[PATCH v2 4/4] ACPI: Change NFIT driver to insert new resource

Toshi Kani
2016-03-02T21:58:29Z

ACPI 6.0 defines persistent memory (PMEM) ranges in multiple
firmware interfaces, e820, EFI, and ACPI NFIT table. This EFI
change, however, leads to hit a bug in the grub bootloader, which
treats EFI_PERSISTENT_MEMORY type as regular memory and corrupts
stored user data [1].

Therefore, BIOS may set generic reserved type in e820 and EFI
to cover PMEM ranges. The kernel can initialize PMEM ranges
from ACPI NFIT table alone.

This scheme causes a problem in the iomem table, though. On x86,
for instance, e820_reserve_resources() initializes top-level entries
(iomem_resource.child) from the e820 table at early boot-time.
This creates "reserved" entry for a PMEM range, which does not allow
region_intersects() to check with PMEM type.

Change acpi_nfit_register_region() to call acpi_nfit_insert_resource(),
which calls devm_insert_resource() to insert a PMEM entry from NFIT
when the iomem table does not have a PMEM entry already. That is,
when a PMEM range is marked as reserved type in e820, it inserts
"Persistent Memory" entry, which results as follows.

+ "Persistent Memory"
+ "reserved"

This allows the EINJ driver, which calls region_intersects() to
check PMEM ranges, to work continuously even if BIOS sets reserved
type (or sets nothing) to PMEM ranges in e820 and EFI.

[1]: https://lists.gnu.org/archive/html/grub-devel/2015-11/msg00209.html
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
drivers/acpi/nfit.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index fb53db1..d97b53f 100644
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -1571,6 +1571,30 @@ static int ars_status_process_records(struct nvdimm_bus *nvdimm_bus,
return 0;
}

+static int acpi_nfit_insert_resource(struct acpi_nfit_desc *acpi_desc,
+ struct nd_region_desc *ndr_desc)
+{
+ struct resource *res, *nd_res = ndr_desc->res;
+ size_t size = nd_res->end - nd_res->start + 1;
+
+ /* No operation if the region is already registered as PMEM */
+ if (region_intersects(nd_res->start, size, IORESOURCE_MEM,
+ IORES_DESC_PERSISTENT_MEMORY) == REGION_INTERSECTS)
+ return 0;
+
+ res = devm_kzalloc(acpi_desc->dev, sizeof(*res), GFP_KERNEL);
+ if (!res)
+ return -ENOMEM;
+
+ res->name = "Persistent Memory";
+ res->start = nd_res->start;
+ res->end = nd_res->end;
+ res->flags = IORESOURCE_MEM;
+ res->desc = IORES_DESC_PERSISTENT_MEMORY;
+
+ return devm_insert_resource(acpi_desc->dev, &iomem_resource, res);
+}
+
static int acpi_nfit_find_poison(struct acpi_nfit_desc *acpi_desc,
struct nd_region_desc *ndr_desc)
{
@@ -1781,6 +1805,12 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc,

nvdimm_bus = acpi_desc->nvdimm_bus;
if (nfit_spa_type(spa) == NFIT_SPA_PM) {
+ rc = acpi_nfit_insert_resource(acpi_desc, ndr_desc);
+ if (rc)
+ dev_warn(acpi_desc->dev,
+ "failed to insert pmem resource to iomem: %d\n",
+ rc);
+
rc = acpi_nfit_find_poison(acpi_desc, ndr_desc);
if (rc) {
dev_err(acpi_desc->dev,