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authorLeonardo Bras <leobras.c@gmail.com>2020-05-18 20:42:45 -0300
committerMichael Ellerman <mpe@ellerman.id.au>2020-06-02 20:59:08 +1000
commitb664db8e3f976d9233cc9ea5e3f8a8c0bcabeb48 (patch)
tree487ddb1404c7fd3029a5e72167fa4010d7ef002e
parent783a015b747f606e803b798eb8b50c73c548691d (diff)
powerpc/rtas: Implement reentrant rtas call
Implement rtas_call_reentrant() for reentrant rtas-calls: "ibm,int-on", "ibm,int-off",ibm,get-xive" and "ibm,set-xive". On LoPAPR Version 1.1 (March 24, 2016), from 7.3.10.1 to 7.3.10.4, items 2 and 3 say: 2 - For the PowerPC External Interrupt option: The * call must be reentrant to the number of processors on the platform. 3 - For the PowerPC External Interrupt option: The * argument call buffer for each simultaneous call must be physically unique. So, these rtas-calls can be called in a lockless way, if using a different buffer for each cpu doing such rtas call. For this, it was suggested to add the buffer (struct rtas_args) in the PACA struct, so each cpu can have it's own buffer. The PACA struct received a pointer to rtas buffer, which is allocated in the memory range available to rtas 32-bit. Reentrant rtas calls are useful to avoid deadlocks in crashing, where rtas-calls are needed, but some other thread crashed holding the rtas.lock. This is a backtrace of a deadlock from a kdump testing environment: #0 arch_spin_lock #1 lock_rtas () #2 rtas_call (token=8204, nargs=1, nret=1, outputs=0x0) #3 ics_rtas_mask_real_irq (hw_irq=4100) #4 machine_kexec_mask_interrupts #5 default_machine_crash_shutdown #6 machine_crash_shutdown #7 __crash_kexec #8 crash_kexec #9 oops_end Signed-off-by: Leonardo Bras <leobras.c@gmail.com> [mpe: Move under #ifdef PSERIES to avoid build breakage] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200518234245.200672-3-leobras.c@gmail.com
-rw-r--r--arch/powerpc/include/asm/paca.h2
-rw-r--r--arch/powerpc/include/asm/rtas.h1
-rw-r--r--arch/powerpc/kernel/paca.c32
-rw-r--r--arch/powerpc/kernel/rtas.c52
-rw-r--r--arch/powerpc/sysdev/xics/ics-rtas.c22
5 files changed, 98 insertions, 11 deletions
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index e3cc9eb9204d..45a839a7c6cf 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -29,6 +29,7 @@
#include <asm/hmi.h>
#include <asm/cpuidle.h>
#include <asm/atomic.h>
+#include <asm/rtas-types.h>
#include <asm-generic/mmiowb_types.h>
@@ -256,6 +257,7 @@ struct paca_struct {
u64 l1d_flush_size;
#endif
#ifdef CONFIG_PPC_PSERIES
+ struct rtas_args *rtas_args_reentrant;
u8 *mce_data_buf; /* buffer to hold per cpu rtas errlog */
#endif /* CONFIG_PPC_PSERIES */
diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index 977e32666015..014968f25f7e 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -236,6 +236,7 @@ extern struct rtas_t rtas;
extern int rtas_token(const char *service);
extern int rtas_service_present(const char *service);
extern int rtas_call(int token, int, int, int *, ...);
+int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...);
void rtas_call_unlocked(struct rtas_args *args, int token, int nargs,
int nret, ...);
extern void __noreturn rtas_restart(char *cmd);
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index 3f91ccaa9c74..8d96169c597e 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -16,6 +16,7 @@
#include <asm/kexec.h>
#include <asm/svm.h>
#include <asm/ultravisor.h>
+#include <asm/rtas.h>
#include "setup.h"
@@ -164,6 +165,30 @@ static struct slb_shadow * __init new_slb_shadow(int cpu, unsigned long limit)
#endif /* CONFIG_PPC_BOOK3S_64 */
+#ifdef CONFIG_PPC_PSERIES
+/**
+ * new_rtas_args() - Allocates rtas args
+ * @cpu: CPU number
+ * @limit: Memory limit for this allocation
+ *
+ * Allocates a struct rtas_args and return it's pointer,
+ * if not in Hypervisor mode
+ *
+ * Return: Pointer to allocated rtas_args
+ * NULL if CPU in Hypervisor Mode
+ */
+static struct rtas_args * __init new_rtas_args(int cpu, unsigned long limit)
+{
+ limit = min_t(unsigned long, limit, RTAS_INSTANTIATE_MAX);
+
+ if (early_cpu_has_feature(CPU_FTR_HVMODE))
+ return NULL;
+
+ return alloc_paca_data(sizeof(struct rtas_args), L1_CACHE_BYTES,
+ limit, cpu);
+}
+#endif /* CONFIG_PPC_PSERIES */
+
/* The Paca is an array with one entry per processor. Each contains an
* lppaca, which contains the information shared between the
* hypervisor and Linux.
@@ -202,6 +227,10 @@ void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int
/* For now -- if we have threads this will be adjusted later */
new_paca->tcd_ptr = &new_paca->tcd;
#endif
+
+#ifdef CONFIG_PPC_PSERIES
+ new_paca->rtas_args_reentrant = NULL;
+#endif
}
/* Put the paca pointer into r13 and SPRG_PACA */
@@ -274,6 +303,9 @@ void __init allocate_paca(int cpu)
#ifdef CONFIG_PPC_BOOK3S_64
paca->slb_shadow_ptr = new_slb_shadow(cpu, limit);
#endif
+#ifdef CONFIG_PPC_PSERIES
+ paca->rtas_args_reentrant = new_rtas_args(cpu, limit);
+#endif
paca_struct_size += sizeof(struct paca_struct);
}
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index c5fa251b8950..a09eba03f180 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -41,6 +41,7 @@
#include <asm/time.h>
#include <asm/mmu.h>
#include <asm/topology.h>
+#include <asm/paca.h>
/* This is here deliberately so it's only used in this file */
void enter_rtas(unsigned long);
@@ -1014,6 +1015,57 @@ out:
free_cpumask_var(offline_mask);
return atomic_read(&data.error);
}
+
+/**
+ * rtas_call_reentrant() - Used for reentrant rtas calls
+ * @token: Token for desired reentrant RTAS call
+ * @nargs: Number of Input Parameters
+ * @nret: Number of Output Parameters
+ * @outputs: Array of outputs
+ * @...: Inputs for desired RTAS call
+ *
+ * According to LoPAR documentation, only "ibm,int-on", "ibm,int-off",
+ * "ibm,get-xive" and "ibm,set-xive" are currently reentrant.
+ * Reentrant calls need their own rtas_args buffer, so not using rtas.args, but
+ * PACA one instead.
+ *
+ * Return: -1 on error,
+ * First output value of RTAS call if (nret > 0),
+ * 0 otherwise,
+ */
+int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...)
+{
+ va_list list;
+ struct rtas_args *args;
+ unsigned long flags;
+ int i, ret = 0;
+
+ if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
+ return -1;
+
+ local_irq_save(flags);
+ preempt_disable();
+
+ /* We use the per-cpu (PACA) rtas args buffer */
+ args = local_paca->rtas_args_reentrant;
+
+ va_start(list, outputs);
+ va_rtas_call_unlocked(args, token, nargs, nret, list);
+ va_end(list);
+
+ if (nret > 1 && outputs)
+ for (i = 0; i < nret - 1; ++i)
+ outputs[i] = be32_to_cpu(args->rets[i + 1]);
+
+ if (nret > 0)
+ ret = be32_to_cpu(args->rets[0]);
+
+ local_irq_restore(flags);
+ preempt_enable();
+
+ return ret;
+}
+
#else /* CONFIG_PPC_PSERIES */
int rtas_ibm_suspend_me(u64 handle)
{
diff --git a/arch/powerpc/sysdev/xics/ics-rtas.c b/arch/powerpc/sysdev/xics/ics-rtas.c
index 6aabc74688a6..4cf18000f07c 100644
--- a/arch/powerpc/sysdev/xics/ics-rtas.c
+++ b/arch/powerpc/sysdev/xics/ics-rtas.c
@@ -50,8 +50,8 @@ static void ics_rtas_unmask_irq(struct irq_data *d)
server = xics_get_irq_server(d->irq, irq_data_get_affinity_mask(d), 0);
- call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq, server,
- DEFAULT_PRIORITY);
+ call_status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq,
+ server, DEFAULT_PRIORITY);
if (call_status != 0) {
printk(KERN_ERR
"%s: ibm_set_xive irq %u server %x returned %d\n",
@@ -60,7 +60,7 @@ static void ics_rtas_unmask_irq(struct irq_data *d)
}
/* Now unmask the interrupt (often a no-op) */
- call_status = rtas_call(ibm_int_on, 1, 1, NULL, hw_irq);
+ call_status = rtas_call_reentrant(ibm_int_on, 1, 1, NULL, hw_irq);
if (call_status != 0) {
printk(KERN_ERR "%s: ibm_int_on irq=%u returned %d\n",
__func__, hw_irq, call_status);
@@ -91,7 +91,7 @@ static void ics_rtas_mask_real_irq(unsigned int hw_irq)
if (hw_irq == XICS_IPI)
return;
- call_status = rtas_call(ibm_int_off, 1, 1, NULL, hw_irq);
+ call_status = rtas_call_reentrant(ibm_int_off, 1, 1, NULL, hw_irq);
if (call_status != 0) {
printk(KERN_ERR "%s: ibm_int_off irq=%u returned %d\n",
__func__, hw_irq, call_status);
@@ -99,8 +99,8 @@ static void ics_rtas_mask_real_irq(unsigned int hw_irq)
}
/* Have to set XIVE to 0xff to be able to remove a slot */
- call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq,
- xics_default_server, 0xff);
+ call_status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq,
+ xics_default_server, 0xff);
if (call_status != 0) {
printk(KERN_ERR "%s: ibm_set_xive(0xff) irq=%u returned %d\n",
__func__, hw_irq, call_status);
@@ -131,7 +131,7 @@ static int ics_rtas_set_affinity(struct irq_data *d,
if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
return -1;
- status = rtas_call(ibm_get_xive, 1, 3, xics_status, hw_irq);
+ status = rtas_call_reentrant(ibm_get_xive, 1, 3, xics_status, hw_irq);
if (status) {
printk(KERN_ERR "%s: ibm,get-xive irq=%u returns %d\n",
@@ -146,8 +146,8 @@ static int ics_rtas_set_affinity(struct irq_data *d,
return -1;
}
- status = rtas_call(ibm_set_xive, 3, 1, NULL,
- hw_irq, irq_server, xics_status[1]);
+ status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL,
+ hw_irq, irq_server, xics_status[1]);
if (status) {
printk(KERN_ERR "%s: ibm,set-xive irq=%u returns %d\n",
@@ -179,7 +179,7 @@ static int ics_rtas_map(struct ics *ics, unsigned int virq)
return -EINVAL;
/* Check if RTAS knows about this interrupt */
- rc = rtas_call(ibm_get_xive, 1, 3, status, hw_irq);
+ rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, hw_irq);
if (rc)
return -ENXIO;
@@ -198,7 +198,7 @@ static long ics_rtas_get_server(struct ics *ics, unsigned long vec)
{
int rc, status[2];
- rc = rtas_call(ibm_get_xive, 1, 3, status, vec);
+ rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, vec);
if (rc)
return -1;
return status[0];