[PATCH] x86/platform/uv/BAU: gracefully disable BAU during panic

[PATCH] x86/platform/uv/BAU: gracefully disable BAU during panic

[Andrew Banman]

When panic happens while BAU is active there is a chance that
outstanding broadcasts tie up BAU resources enough to cause timeouts in
the UV ASIC. These timeouts are hardware errors that immediately bring
down the system, preventing kdump from completing.

Add uv_bau_crash_shutdown() to bring BAU to quiescence during panic before
continuing with the native crash shutdown. Assign uv_bau_crash_shutdown
to machine_ops during init.

Signed-off-by: Andrew Banman <abanman@hpe.com>
---
 arch/x86/platform/uv/tlb_uv.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index b36caae..e7f9aea 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -22,6 +22,7 @@
 #include <asm/tsc.h>
 #include <asm/irq_vectors.h>
 #include <asm/timer.h>
+#include <asm/reboot.h>
 
 static struct bau_operations ops __ro_after_init;
 
@@ -2197,6 +2198,32 @@ static int __init init_per_cpu(int nuvhubs, int base_part_pnode)
 	.wait_completion         = uv4_wait_completion,
 };
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * Bring BAU to quiesence by disabling future broadcasts and abandoning
+ * current broadcasts during panic.
+ */
+void uv_bau_crash_shutdown(struct pt_regs *regs)
+{
+	set_bau_off();
+	nobau_perm = 1;
+
+	for_each_possible_blade(uvhub) {
+		if (!uv_blade_nr_possible_cpus(uvhub))
+			continue;
+		int pnode = uv_blade_to_pnode(uvhub);
+		/* Set STATUS registers to idle to free source cpus */
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_0, 0x0);
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_1, 0x0);
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_2, 0x0);
+		/* Clear TIMEOUT and PENDING bits to free up BAU resources */
+		ops.write_g_sw_ack(pnode, ops.read_g_sw_ack(pnode) & 0xFFFF);
+	}
+
+	native_machine_crash_shutdown(regs);
+}
+#endif
+
 /*
  * Initialization of BAU-related structures
  */
@@ -2269,6 +2296,10 @@ static int __init uv_bau_init(void)
 		}
 	}
 
+#ifdef CONFIG_KEXEC_CORE
+	machine_ops.crash_shutdown = uv_bau_crash_shutdown;
+#endif
+
 	return 0;
 
 err_bau_disable:
-- 
1.8.2.1

Re: [PATCH] x86/platform/uv/BAU: gracefully disable BAU during panic

[Greg KH]

On Sun, Jun 03, 2018 at 11:42:32AM -0500, Andrew Banman wrote:
> When panic happens while BAU is active there is a chance that
> outstanding broadcasts tie up BAU resources enough to cause timeouts in
> the UV ASIC. These timeouts are hardware errors that immediately bring
> down the system, preventing kdump from completing.
> 
> Add uv_bau_crash_shutdown() to bring BAU to quiescence during panic before
> continuing with the native crash shutdown. Assign uv_bau_crash_shutdown
> to machine_ops during init.
> 
> Signed-off-by: Andrew Banman <abanman@hpe.com>
> ---
>  arch/x86/platform/uv/tlb_uv.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Re: [PATCH] x86/platform/uv/BAU: gracefully disable BAU during panic

[kbuild test robot]

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Hi Andrew,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/auto-latest]
[also build test ERROR on v4.17-rc7 next-20180601]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Andrew-Banman/x86-platform-uv-BAU-gracefully-disable-BAU-during-panic/20180604-005410
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All error/warnings (new ones prefixed by >>):

   In file included from arch/x86/platform/uv/tlb_uv.c:19:0:
   arch/x86/platform/uv/tlb_uv.c: In function 'uv_bau_crash_shutdown':
>> arch/x86/platform/uv/tlb_uv.c:2211:26: error: 'uvhub' undeclared (first use in this function)
     for_each_possible_blade(uvhub) {
                             ^
   arch/x86/include/asm/uv/uv_hub.h:437:8: note: in definition of macro 'for_each_possible_blade'
     for ((bid) = 0; (bid) < uv_num_possible_blades(); (bid)++)
           ^~~
   arch/x86/platform/uv/tlb_uv.c:2211:26: note: each undeclared identifier is reported only once for each function it appears in
     for_each_possible_blade(uvhub) {
                             ^
   arch/x86/include/asm/uv/uv_hub.h:437:8: note: in definition of macro 'for_each_possible_blade'
     for ((bid) = 0; (bid) < uv_num_possible_blades(); (bid)++)
           ^~~
>> arch/x86/platform/uv/tlb_uv.c:2214:3: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
      int pnode = uv_blade_to_pnode(uvhub);
      ^~~

vim +/uvhub +2211 arch/x86/platform/uv/tlb_uv.c

  2200	
  2201	#ifdef CONFIG_KEXEC_CORE
  2202	/*
  2203	 * Bring BAU to quiesence by disabling future broadcasts and abandoning
  2204	 * current broadcasts during panic.
  2205	 */
  2206	void uv_bau_crash_shutdown(struct pt_regs *regs)
  2207	{
  2208		set_bau_off();
  2209		nobau_perm = 1;
  2210	
> 2211		for_each_possible_blade(uvhub) {
  2212			if (!uv_blade_nr_possible_cpus(uvhub))
  2213				continue;
> 2214			int pnode = uv_blade_to_pnode(uvhub);
  2215			/* Set STATUS registers to idle to free source cpus */
  2216			write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_0, 0x0);
  2217			write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_1, 0x0);
  2218			write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_2, 0x0);
  2219			/* Clear TIMEOUT and PENDING bits to free up BAU resources */
  2220			ops.write_g_sw_ack(pnode, ops.read_g_sw_ack(pnode) & 0xFFFF);
  2221		}
  2222	
  2223		native_machine_crash_shutdown(regs);
  2224	}
  2225	#endif
  2226	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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[PATCH] x86/platform/uv/BAU: gracefully disable BAU during panic

[Andrew Banman]

When we panic while the BAU is active, outstanding broadcasts may go
un-acknowledged by the kernel. These broadcasts cause timeouts in the
UV ASIC that tie up BAU resources, which may cause a fatal error that
brings down the system, thereby crashing the kdump kexec.

Add uv_bau_crash_shutdown() to bring BAU to quiescence ahead of the crash
shutdown routine saved in smp machine_ops. Assign uv_bau_crash_shutdown
to machine_ops during init.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Mike Travis <mike.travis@hpe.com>
Signed-off-by: Andrew Banman <abanman@hpe.com>
---
 arch/x86/platform/uv/tlb_uv.c | 49 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index e26dfad..dae6b3c 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -22,8 +22,13 @@
 #include <asm/tsc.h>
 #include <asm/irq_vectors.h>
 #include <asm/timer.h>
+#include <asm/reboot.h>
 
 static struct bau_operations ops __ro_after_init;
+#ifdef CONFIG_KEXEC_CORE
+static void (*crash_shutdown)(struct pt_regs *regs) __ro_after_init;
+static bool crash_in_progress;
+#endif
 
 /* timeouts in nanoseconds (indexed by UVH_AGING_PRESCALE_SEL urgency7 30:28) */
 static const int timeout_base_ns[] = {
@@ -2195,6 +2200,44 @@ static int __init init_per_cpu(int nuvhubs, int base_part_pnode)
 	.wait_completion         = uv4_wait_completion,
 };
 
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * Bring BAU to quiesence by abandoning current broadcasts and freeing up
+ * resources needed by firmware-initiated BAU broadcasts.
+ */
+void uv_bau_crash_shutdown(struct pt_regs *regs)
+{
+	int pnode = 0;
+	int uvhub = 0;
+
+	if (crash_in_progress)
+		return;
+	crash_in_progress = true;
+
+	/*
+	 * Don't bother turning off BAU in the per-cpu structs. We free up
+	 * enough INTD resources to accommodate any new broadcasts that
+	 * may (however unlikley) start up before we complete the panic,
+	 * without tying up FW-initiated General Broadcasts that must not
+	 * time out.
+	 */
+
+	for_each_possible_blade(uvhub) {
+		if (!uv_blade_nr_possible_cpus(uvhub))
+			continue;
+		pnode = uv_blade_to_pnode(uvhub);
+		/* Set STATUS registers to idle to free source cpus */
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_0, 0x0);
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_1, 0x0);
+		write_gmmr(pnode, UVH_LB_BAU_SB_ACTIVATION_STATUS_2, 0x0);
+		/* Clear TIMEOUT and PENDING bits to free up BAU resources */
+		ops.write_g_sw_ack(pnode, ops.read_g_sw_ack(pnode) & 0xFFFF);
+	}
+
+	crash_shutdown(regs);
+}
+#endif
+
 /*
  * Initialization of BAU-related structures
  */
@@ -2267,6 +2310,12 @@ static int __init uv_bau_init(void)
 		}
 	}
 
+#ifdef CONFIG_KEXEC_CORE
+	crash_shutdown = machine_ops.crash_shutdown;
+	machine_ops.crash_shutdown = uv_bau_crash_shutdown;
+	crash_in_progress = false;
+#endif
+
 	return 0;
 
 err_bau_disable:
-- 
1.8.2.1