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Subject[PATCH v2 6/6] nfit/ars: Avoid stale ARS results
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Date
Gate ARS result consumption on whether the OS issued start-ARS since the
previous consumption. The BIOS may only clear its result buffers after a
successful start-ARS.

Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/acpi/nfit/core.c | 17 ++++++++++++++++-
drivers/acpi/nfit/nfit.h | 1 +
2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 629cf91649d2..5c9eb8d700d3 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2652,7 +2652,10 @@ static int ars_start(struct acpi_nfit_desc *acpi_desc,

if (rc < 0)
return rc;
- return cmd_rc;
+ if (cmd_rc < 0)
+ return cmd_rc;
+ set_bit(ARS_VALID, &acpi_desc->scrub_flags);
+ return 0;
}

static int ars_continue(struct acpi_nfit_desc *acpi_desc)
@@ -2745,6 +2748,17 @@ static int ars_status_process_records(struct acpi_nfit_desc *acpi_desc)
*/
if (ars_status->out_length < 44)
return 0;
+
+ /*
+ * Ignore potentially stale results that are only refreshed
+ * after a start-ARS event.
+ */
+ if (!test_and_clear_bit(ARS_VALID, &acpi_desc->scrub_flags)) {
+ dev_dbg(acpi_desc->dev, "skip %d stale records\n",
+ ars_status->num_records);
+ return 0;
+ }
+
for (i = 0; i < ars_status->num_records; i++) {
/* only process full records */
if (ars_status->out_length
@@ -3229,6 +3243,7 @@ static int acpi_nfit_register_regions(struct acpi_nfit_desc *acpi_desc)
struct nfit_spa *nfit_spa;
int rc;

+ set_bit(ARS_VALID, &acpi_desc->scrub_flags);
list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
switch (nfit_spa_type(nfit_spa->spa)) {
case NFIT_SPA_VOLATILE:
diff --git a/drivers/acpi/nfit/nfit.h b/drivers/acpi/nfit/nfit.h
index d14bad687fb8..0cbe5009eb2c 100644
--- a/drivers/acpi/nfit/nfit.h
+++ b/drivers/acpi/nfit/nfit.h
@@ -213,6 +213,7 @@ struct nfit_mem {
enum scrub_flags {
ARS_BUSY,
ARS_CANCEL,
+ ARS_VALID,
ARS_POLL,
};

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