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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
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783a015b74
commit
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5 changed files with 98 additions and 11 deletions
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@ -29,6 +29,7 @@
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#include <asm/hmi.h>
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#include <asm/cpuidle.h>
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#include <asm/atomic.h>
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#include <asm/rtas-types.h>
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#include <asm-generic/mmiowb_types.h>
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@ -256,6 +257,7 @@ struct paca_struct {
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u64 l1d_flush_size;
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#endif
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#ifdef CONFIG_PPC_PSERIES
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struct rtas_args *rtas_args_reentrant;
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u8 *mce_data_buf; /* buffer to hold per cpu rtas errlog */
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#endif /* CONFIG_PPC_PSERIES */
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@ -236,6 +236,7 @@ extern struct rtas_t rtas;
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extern int rtas_token(const char *service);
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extern int rtas_service_present(const char *service);
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extern int rtas_call(int token, int, int, int *, ...);
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int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...);
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void rtas_call_unlocked(struct rtas_args *args, int token, int nargs,
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int nret, ...);
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extern void __noreturn rtas_restart(char *cmd);
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@ -16,6 +16,7 @@
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#include <asm/kexec.h>
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#include <asm/svm.h>
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#include <asm/ultravisor.h>
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#include <asm/rtas.h>
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#include "setup.h"
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@ -164,6 +165,30 @@ static struct slb_shadow * __init new_slb_shadow(int cpu, unsigned long limit)
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#endif /* CONFIG_PPC_BOOK3S_64 */
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#ifdef CONFIG_PPC_PSERIES
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/**
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* new_rtas_args() - Allocates rtas args
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* @cpu: CPU number
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* @limit: Memory limit for this allocation
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*
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* Allocates a struct rtas_args and return it's pointer,
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* if not in Hypervisor mode
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*
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* Return: Pointer to allocated rtas_args
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* NULL if CPU in Hypervisor Mode
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*/
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static struct rtas_args * __init new_rtas_args(int cpu, unsigned long limit)
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{
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limit = min_t(unsigned long, limit, RTAS_INSTANTIATE_MAX);
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if (early_cpu_has_feature(CPU_FTR_HVMODE))
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return NULL;
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return alloc_paca_data(sizeof(struct rtas_args), L1_CACHE_BYTES,
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limit, cpu);
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}
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#endif /* CONFIG_PPC_PSERIES */
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/* The Paca is an array with one entry per processor. Each contains an
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* lppaca, which contains the information shared between the
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* hypervisor and Linux.
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@ -202,6 +227,10 @@ void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int
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/* For now -- if we have threads this will be adjusted later */
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new_paca->tcd_ptr = &new_paca->tcd;
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#endif
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#ifdef CONFIG_PPC_PSERIES
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new_paca->rtas_args_reentrant = NULL;
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#endif
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}
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/* Put the paca pointer into r13 and SPRG_PACA */
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@ -273,6 +302,9 @@ void __init allocate_paca(int cpu)
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#endif
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#ifdef CONFIG_PPC_BOOK3S_64
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paca->slb_shadow_ptr = new_slb_shadow(cpu, limit);
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#endif
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#ifdef CONFIG_PPC_PSERIES
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paca->rtas_args_reentrant = new_rtas_args(cpu, limit);
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#endif
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paca_struct_size += sizeof(struct paca_struct);
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}
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@ -41,6 +41,7 @@
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#include <asm/time.h>
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#include <asm/mmu.h>
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#include <asm/topology.h>
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#include <asm/paca.h>
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/* This is here deliberately so it's only used in this file */
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void enter_rtas(unsigned long);
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@ -1014,6 +1015,57 @@ int rtas_ibm_suspend_me(u64 handle)
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free_cpumask_var(offline_mask);
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return atomic_read(&data.error);
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}
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/**
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* rtas_call_reentrant() - Used for reentrant rtas calls
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* @token: Token for desired reentrant RTAS call
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* @nargs: Number of Input Parameters
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* @nret: Number of Output Parameters
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* @outputs: Array of outputs
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* @...: Inputs for desired RTAS call
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*
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* According to LoPAR documentation, only "ibm,int-on", "ibm,int-off",
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* "ibm,get-xive" and "ibm,set-xive" are currently reentrant.
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* Reentrant calls need their own rtas_args buffer, so not using rtas.args, but
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* PACA one instead.
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*
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* Return: -1 on error,
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* First output value of RTAS call if (nret > 0),
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* 0 otherwise,
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*/
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int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...)
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{
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va_list list;
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struct rtas_args *args;
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unsigned long flags;
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int i, ret = 0;
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if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
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return -1;
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local_irq_save(flags);
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preempt_disable();
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/* We use the per-cpu (PACA) rtas args buffer */
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args = local_paca->rtas_args_reentrant;
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va_start(list, outputs);
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va_rtas_call_unlocked(args, token, nargs, nret, list);
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va_end(list);
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if (nret > 1 && outputs)
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for (i = 0; i < nret - 1; ++i)
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outputs[i] = be32_to_cpu(args->rets[i + 1]);
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if (nret > 0)
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ret = be32_to_cpu(args->rets[0]);
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local_irq_restore(flags);
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preempt_enable();
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return ret;
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}
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#else /* CONFIG_PPC_PSERIES */
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int rtas_ibm_suspend_me(u64 handle)
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{
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@ -50,8 +50,8 @@ static void ics_rtas_unmask_irq(struct irq_data *d)
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server = xics_get_irq_server(d->irq, irq_data_get_affinity_mask(d), 0);
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call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq, server,
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DEFAULT_PRIORITY);
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call_status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq,
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server, DEFAULT_PRIORITY);
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if (call_status != 0) {
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printk(KERN_ERR
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"%s: ibm_set_xive irq %u server %x returned %d\n",
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@ -60,7 +60,7 @@ static void ics_rtas_unmask_irq(struct irq_data *d)
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}
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/* Now unmask the interrupt (often a no-op) */
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call_status = rtas_call(ibm_int_on, 1, 1, NULL, hw_irq);
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call_status = rtas_call_reentrant(ibm_int_on, 1, 1, NULL, hw_irq);
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if (call_status != 0) {
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printk(KERN_ERR "%s: ibm_int_on irq=%u returned %d\n",
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__func__, hw_irq, call_status);
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@ -91,7 +91,7 @@ static void ics_rtas_mask_real_irq(unsigned int hw_irq)
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if (hw_irq == XICS_IPI)
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return;
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call_status = rtas_call(ibm_int_off, 1, 1, NULL, hw_irq);
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call_status = rtas_call_reentrant(ibm_int_off, 1, 1, NULL, hw_irq);
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if (call_status != 0) {
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printk(KERN_ERR "%s: ibm_int_off irq=%u returned %d\n",
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__func__, hw_irq, call_status);
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@ -99,8 +99,8 @@ static void ics_rtas_mask_real_irq(unsigned int hw_irq)
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}
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/* Have to set XIVE to 0xff to be able to remove a slot */
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call_status = rtas_call(ibm_set_xive, 3, 1, NULL, hw_irq,
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xics_default_server, 0xff);
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call_status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq,
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xics_default_server, 0xff);
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if (call_status != 0) {
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printk(KERN_ERR "%s: ibm_set_xive(0xff) irq=%u returned %d\n",
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__func__, hw_irq, call_status);
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@ -131,7 +131,7 @@ static int ics_rtas_set_affinity(struct irq_data *d,
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if (hw_irq == XICS_IPI || hw_irq == XICS_IRQ_SPURIOUS)
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return -1;
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status = rtas_call(ibm_get_xive, 1, 3, xics_status, hw_irq);
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status = rtas_call_reentrant(ibm_get_xive, 1, 3, xics_status, hw_irq);
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if (status) {
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printk(KERN_ERR "%s: ibm,get-xive irq=%u returns %d\n",
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@ -146,8 +146,8 @@ static int ics_rtas_set_affinity(struct irq_data *d,
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return -1;
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}
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status = rtas_call(ibm_set_xive, 3, 1, NULL,
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hw_irq, irq_server, xics_status[1]);
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status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL,
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hw_irq, irq_server, xics_status[1]);
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if (status) {
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printk(KERN_ERR "%s: ibm,set-xive irq=%u returns %d\n",
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@ -179,7 +179,7 @@ static int ics_rtas_map(struct ics *ics, unsigned int virq)
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return -EINVAL;
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/* Check if RTAS knows about this interrupt */
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rc = rtas_call(ibm_get_xive, 1, 3, status, hw_irq);
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rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, hw_irq);
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if (rc)
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return -ENXIO;
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@ -198,7 +198,7 @@ static long ics_rtas_get_server(struct ics *ics, unsigned long vec)
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{
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int rc, status[2];
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rc = rtas_call(ibm_get_xive, 1, 3, status, vec);
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rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, vec);
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if (rc)
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return -1;
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return status[0];
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