linux-kernel - [PATCH 5.4 284/434] EDAC/ghes: Fix grain calculation

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Message-Id: <20191229172720.814013410@linuxfoundation.org>
Date:   Sun, 29 Dec 2019 18:25:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Morse <james.morse@....com>,
        Robert Richter <rrichter@...vell.com>,
        Borislav Petkov <bp@...e.de>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 284/434] EDAC/ghes: Fix grain calculation

From: Robert Richter <rrichter@...vell.com>

[ Upstream commit 7088e29e0423d3195e09079b4f849ec4837e5a75 ]

The current code to convert a physical address mask to a grain
(defined as granularity in bytes) is:

	e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);

This is broken in several ways:

1) It calculates to wrong grain values. E.g., a physical address mask
of ~0xfff should give a grain of 0x1000. Without considering
PAGE_MASK, there is an off-by-one. Things are worse when also
filtering it with ~PAGE_MASK. This will calculate to a grain with the
upper bits set. In the example it even calculates to ~0.

2) The grain does not depend on and is unrelated to the kernel's
page-size. The page-size only matters when unmapping memory in
memory_failure(). Smaller grains are wrongly rounded up to the
page-size, on architectures with a configurable page-size (e.g. arm64)
this could round up to the even bigger page-size of the hypervisor.

Fix this with:

	e->grain = ~mem_err->physical_addr_mask + 1;

The grain_bits are defined as:

	grain = 1 << grain_bits;

Change also the grain_bits calculation accordingly, it is the same
formula as in edac_mc.c now and the code can be unified.

The value in ->physical_addr_mask coming from firmware is assumed to
be contiguous, but this is not sanity-checked. However, in case the
mask is non-contiguous, a conversion to grain_bits effectively
converts the grain bit mask to a power of 2 by rounding it up.

Suggested-by: James Morse <james.morse@....com>
Signed-off-by: Robert Richter <rrichter@...vell.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc: "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Cc: Tony Luck <tony.luck@...el.com>
Link: https://lkml.kernel.org/r/20191106093239.25517-11-rrichter@marvell.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/edac/ghes_edac.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c
index 296e714bf553..523dd56a798c 100644
--- a/drivers/edac/ghes_edac.c
+++ b/drivers/edac/ghes_edac.c
@@ -231,6 +231,7 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 	/* Cleans the error report buffer */
 	memset(e, 0, sizeof (*e));
 	e->error_count = 1;
+	e->grain = 1;
 	strcpy(e->label, "unknown label");
 	e->msg = pvt->msg;
 	e->other_detail = pvt->other_detail;
@@ -326,7 +327,7 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 
 	/* Error grain */
 	if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
-		e->grain = ~(mem_err->physical_addr_mask & ~PAGE_MASK);
+		e->grain = ~mem_err->physical_addr_mask + 1;
 
 	/* Memory error location, mapped on e->location */
 	p = e->location;
@@ -442,8 +443,13 @@ void ghes_edac_report_mem_error(int sev, struct cper_sec_mem_err *mem_err)
 	if (p > pvt->other_detail)
 		*(p - 1) = '\0';
 
+	/* Sanity-check driver-supplied grain value. */
+	if (WARN_ON_ONCE(!e->grain))
+		e->grain = 1;
+
+	grain_bits = fls_long(e->grain - 1);
+
 	/* Generate the trace event */
-	grain_bits = fls_long(e->grain);
 	snprintf(pvt->detail_location, sizeof(pvt->detail_location),
 		 "APEI location: %s %s", e->location, e->other_detail);
 	trace_mc_event(type, e->msg, e->label, e->error_count,
-- 
2.20.1