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

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Date:	Wed,  2 Mar 2016 15:50:56 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	mingo@...nel.org, bp@...e.de, dan.j.williams@...el.com,
	rjw@...ysocki.net, akpm@...ux-foundation.org
Cc:	linux-nvdimm@...ts.01.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Toshi Kani <toshi.kani@....com>
Subject: [PATCH v2 4/4] ACPI: Change NFIT driver to insert new resource

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@....com>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-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,