On 6/2/22 00:48, Scott Cheloha wrote:
On Wed, May 25, 2022 at 04:35:11PM +1000, Alexey Kardashevskiy wrote:
On 5/21/22 04:35, Scott Cheloha wrote:
PAPR v2.12 defines a new hypercall, H_WATCHDOG. The hypercall permits
guest control of one or more virtual watchdog timers. The timers have
millisecond granularity. The guest is terminated when a timer
expires.
This patch adds a watchdog driver for these timers, "pseries-wdt".
pseries_wdt_probe() currently assumes the existence of only one
platform device and always assigns it watchdogNumber 1. If we ever
expose more than one timer to userspace we will need to devise a way
to assign a distinct watchdogNumber to each platform device at device
registration time.
This one should go before 4/4 in the series for bisectability.
What is platform_device_register_simple("pseries-wdt",...) going to do
without the driver?
This is a chicken-and-egg problem without an obvious solution. A
device without a driver is a body without a soul. A driver without a
device is a ghost without a machine.
... or something like that, don't quote me :)
Absent some very compelling reasoning, I would like to keep the
current order. It feels logical to me to keep the powerpc/pseries
patches adjacent and prior to the watchdog driver patch.
Signed-off-by: Scott Cheloha <cheloha@xxxxxxxxxxxxx>
---
.../watchdog/watchdog-parameters.rst | 12 +
drivers/watchdog/Kconfig | 8 +
drivers/watchdog/Makefile | 1 +
drivers/watchdog/pseries-wdt.c | 337 ++++++++++++++++++
4 files changed, 358 insertions(+)
create mode 100644 drivers/watchdog/pseries-wdt.c
diff --git a/Documentation/watchdog/watchdog-parameters.rst b/Documentation/watchdog/watchdog-parameters.rst
index 223c99361a30..4ffe725e796c 100644
--- a/Documentation/watchdog/watchdog-parameters.rst
+++ b/Documentation/watchdog/watchdog-parameters.rst
@@ -425,6 +425,18 @@ pnx833x_wdt:
-------------------------------------------------
+pseries-wdt:
+ action:
+ Action taken when watchdog expires: 1 (power off), 2 (restart),
+ 3 (dump and restart). (default=2)
+ timeout:
+ Initial watchdog timeout in seconds. (default=60)
+ nowayout:
+ Watchdog cannot be stopped once started.
+ (default=kernel config parameter)
+
+-------------------------------------------------
+
rc32434_wdt:
timeout:
Watchdog timeout value, in seconds (default=20)
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index c4e82a8d863f..06b412603f3e 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1932,6 +1932,14 @@ config MEN_A21_WDT
# PPC64 Architecture
+config PSERIES_WDT
+ tristate "POWER Architecture Platform Watchdog Timer"
+ depends on PPC_PSERIES
+ select WATCHDOG_CORE
+ help
+ Driver for virtual watchdog timers provided by PAPR
+ hypervisors (e.g. PowerVM, KVM).
+
config WATCHDOG_RTAS
tristate "RTAS watchdog"
depends on PPC_RTAS
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index f7da867e8782..f35660409f17 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -184,6 +184,7 @@ obj-$(CONFIG_BOOKE_WDT) += booke_wdt.o
obj-$(CONFIG_MEN_A21_WDT) += mena21_wdt.o
# PPC64 Architecture
+obj-$(CONFIG_PSERIES_WDT) += pseries-wdt.o
obj-$(CONFIG_WATCHDOG_RTAS) += wdrtas.o
# S390 Architecture
diff --git a/drivers/watchdog/pseries-wdt.c b/drivers/watchdog/pseries-wdt.c
new file mode 100644
index 000000000000..f41bc4d3b7a2
--- /dev/null
+++ b/drivers/watchdog/pseries-wdt.c
@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2022 International Business Machines, Inc.
+ */
+
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define DRV_NAME "pseries-wdt"
+
+/*
+ * The PAPR's MSB->LSB bit ordering is 0->63. These macros simplify
+ * defining bitfields as described in the PAPR without needing to
+ * transpose values to the more C-like 63->0 ordering.
+ */
+#define SETFIELD(_v, _b, _e) \
+ (((unsigned long)(_v) << PPC_BITLSHIFT(_e)) & PPC_BITMASK((_b), (_e)))
+#define GETFIELD(_v, _b, _e) \
+ (((unsigned long)(_v) & PPC_BITMASK((_b), (_e))) >> PPC_BITLSHIFT(_e))
+
+/*
+ * H_WATCHDOG Hypercall Input
+ *
+ * R4: "flags":
+ *
+ * A 64-bit value structured as follows:
+ *
+ * Bits 0-46: Reserved (must be zero).
+ */
+#define PSERIES_WDTF_RESERVED PPC_BITMASK(0, 46)
+
+/*
+ * Bit 47: "leaveOtherWatchdogsRunningOnTimeout"
+ *
+ * 0 Stop outstanding watchdogs on timeout.
+ * 1 Leave outstanding watchdogs running on timeout.
+ */
+#define PSERIES_WDTF_LEAVE_OTHER PPC_BIT(47)
+
+/*
+ * Bits 48-55: "operation"
+ *
+ * 0x01 Start Watchdog
+ * 0x02 Stop Watchdog
+ * 0x03 Query Watchdog Capabilities
+ * 0x04 Query Watchdog LPM Requirement
+ */
+#define PSERIES_WDTF_OP(op) SETFIELD((op), 48, 55)
+#define PSERIES_WDTF_OP_START PSERIES_WDTF_OP(0x1)
+#define PSERIES_WDTF_OP_STOP PSERIES_WDTF_OP(0x2)
+#define PSERIES_WDTF_OP_QUERY PSERIES_WDTF_OP(0x3)
+#define PSERIES_WDTF_OP_QUERY_LPM PSERIES_WDTF_OP(0x4)
+
+/*
+ * Bits 56-63: "timeoutAction"
+ *
+ * 0x01 Hard poweroff
+ * 0x02 Hard restart
+ * 0x03 Dump restart
+ */
+#define PSERIES_WDTF_ACTION(ac) SETFIELD(ac, 56, 63)
+#define PSERIES_WDTF_ACTION_HARD_POWEROFF PSERIES_WDTF_ACTION(0x1)
+#define PSERIES_WDTF_ACTION_HARD_RESTART PSERIES_WDTF_ACTION(0x2)
+#define PSERIES_WDTF_ACTION_DUMP_RESTART PSERIES_WDTF_ACTION(0x3)
+
+/*
+ * R5: "watchdogNumber":
+ *
+ * The target watchdog. Watchdog numbers are 1-based. The
+ * maximum supported watchdog number may be obtained via the
+ * "Query Watchdog Capabilities" operation.
+ *
+ * This input is ignored for the "Query Watchdog Capabilities"
+ * operation.
+ *
+ * R6: "timeoutInMs":
+ *
+ * The timeout in milliseconds. The minimum supported timeout may
+ * be obtained via the "Query Watchdog Capabilities" operation.
+ *
+ * This input is ignored for the "Stop Watchdog", "Query Watchdog
+ * Capabilities", and "Query Watchdog LPM Requirement" operations.
+ */
+
+/*
+ * H_WATCHDOG Hypercall Output
+ *
+ * R3: Return code
+ *
+ * H_SUCCESS The operation completed.
+ *
+ * H_BUSY The hypervisor is too busy; retry the operation.
+ *
+ * H_PARAMETER The given "flags" are somehow invalid. Either the
+ * "operation" or "timeoutAction" is invalid, or a
+ * reserved bit is set.
+ *
+ * H_P2 The given "watchdogNumber" is zero or exceeds the
+ * supported maximum value.
+ *
+ * H_P3 The given "timeoutInMs" is below the supported
+ * minimum value.
+ *
+ * H_NOOP The given "watchdogNumber" is already stopped.
+ *
+ * H_HARDWARE The operation failed for ineffable reasons.
+ *
+ * H_FUNCTION The H_WATCHDOG hypercall is not supported by this
+ * hypervisor.
+ *
+ * R4:
+ *
+ * - For the "Query Watchdog Capabilities" operation, a 64-bit
+ * value structured as follows:
+ *
+ * Bits 0-15: The minimum supported timeout in milliseconds.
+ * Bits 16-31: The number of watchdogs supported.
+ * Bits 32-63: Reserved.
+ */
+#define PSERIES_WDTQ_MIN_TIMEOUT(cap) GETFIELD((cap), 0, 15)
+#define PSERIES_WDTQ_MAX_NUMBER(cap) GETFIELD((cap), 16, 31)
+#define PSERIES_WDTQ_RESERVED PPC_BITMASK(32, 63)
PSERIES_WDTQ_RESERVED is not needed as there is a comment above.
The *_RESERVED macros are from your draft patch. I will remove them,
though, we aren't actually using them.
Well, I was thinking of testing the reserved bits to be all zero but the
interface may grow so yeah, drop it.
I will trim up the big comment for v2, too. It's just going to rot
otherwise. You need to read the PAPR to review the hypercalls,
anyway.
+
+/*
+ * - For the "Query Watchdog LPM Requirement" operation:
+ *
+ * 1 The given "watchdogNumber" must be stopped prior to
+ * suspending.
+ *
+ * 2 The given "watchdogNumber" does not have to be stopped
+ * prior to suspending.
+ */
+#define PSERIES_WDTQL_MUST_STOP 1
+#define PSERIES_WDTQL_NEED_NOT_STOP 2
+
+static unsigned long action = PSERIES_WDTF_ACTION_HARD_RESTART;
+
+static int action_get(char *buf, const struct kernel_param *kp)
+{
+ int val;
+
+ switch (action) {
+ case PSERIES_WDTF_ACTION_HARD_POWEROFF:
+ val = 1;
+ break;
+ case PSERIES_WDTF_ACTION_HARD_RESTART:
+ val = 2;
+ break;
+ case PSERIES_WDTF_ACTION_DUMP_RESTART:
+ val = 3;
+ break;
+ default:
+ return -EINVAL;
+ }
+ return sprintf(buf, "%d\n", val);
+}
+
+static int action_set(const char *val, const struct kernel_param *kp)
+{
+ int choice;
+
+ if (kstrtoint(val, 10, &choice))
+ return -EINVAL;
+ switch (choice) {
+ case 1:
+ action = PSERIES_WDTF_ACTION_HARD_POWEROFF;
+ return 0;
+ case 2:
+ action = PSERIES_WDTF_ACTION_HARD_RESTART;
+ return 0;
+ case 3:
+ action = PSERIES_WDTF_ACTION_DUMP_RESTART;
+ return 0;
+ }
+ return -EINVAL;
+}
+
+static const struct kernel_param_ops action_ops = {
+ .get = action_get,
+ .set = action_set,
+};
+module_param_cb(action, &action_ops, NULL, 0444);
0644 here and below?
I do not want these changing at runtime. 0444 is the right thing.
If the driver is compiled into vmlinux, then I'll have to have stuff in
/etc/modprobe.d (or kernel cmdline) and reboot the kernel, annoying for
testing/debugging. Not a big deal but I just do not see what 0444 buys
compared to 0644 or (mostly used for watchdogs) 0.
--
Alexey
