The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f88aabad33ea22be2ce1c60d8901942e4e2a9edb Mon Sep 17 00:00:00 2001 From: Nathan Lynch nathanl@linux.ibm.com Date: Wed, 7 Sep 2022 17:01:11 -0500 Subject: [PATCH] Revert "powerpc/rtas: Implement reentrant rtas call"

At the time this was submitted by Leonardo, I confirmed -- or thought I had confirmed -- with PowerVM partition firmware development that the following RTAS functions:

- ibm,get-xive - ibm,int-off - ibm,int-on - ibm,set-xive

were safe to call on multiple CPUs simultaneously, not only with respect to themselves as indicated by PAPR, but with arbitrary other RTAS calls:

https://lore.kernel.org/linuxppc-dev/875zcy2v8o.fsf@linux.ibm.com/

Recent discussion with firmware development makes it clear that this is not true, and that the code in commit b664db8e3f97 ("powerpc/rtas: Implement reentrant rtas call") is unsafe, likely explaining several strange bugs we've seen in internal testing involving DLPAR and LPM. These scenarios use ibm,configure-connector, whose internal state can be corrupted by the concurrent use of the "reentrant" functions, leading to symptoms like endless busy statuses from RTAS.

Fixes: b664db8e3f97 ("powerpc/rtas: Implement reentrant rtas call") Cc: stable@vger.kernel.org # v5.8+ Signed-off-by: Nathan Lynch nathanl@linux.ibm.com Reviewed-by: Laurent Dufour laurent.dufour@fr.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20220907220111.223267-1-nathanl@linux.ibm.com

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index 4d7aaab82702..3537b0500f4d 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -263,7 +263,6 @@ 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 00531af17ce0..56319aea646e 100644 --- a/arch/powerpc/include/asm/rtas.h +++ b/arch/powerpc/include/asm/rtas.h @@ -240,7 +240,6 @@ 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 ba593fd60124..dfd097b79160 100644 --- a/arch/powerpc/kernel/paca.c +++ b/arch/powerpc/kernel/paca.c @@ -16,7 +16,6 @@ #include <asm/kexec.h> #include <asm/svm.h> #include <asm/ultravisor.h> -#include <asm/rtas.h>

#include "setup.h"

@@ -170,30 +169,6 @@ static struct slb_shadow * __init new_slb_shadow(int cpu, unsigned long limit) } #endif /* CONFIG_PPC_64S_HASH_MMU */

-#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. @@ -232,10 +207,6 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu) /* 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 */ @@ -307,9 +278,6 @@ void __init allocate_paca(int cpu) #endif #ifdef CONFIG_PPC_64S_HASH_MMU 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 693133972294..0b8a858aa847 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -43,7 +43,6 @@ #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); @@ -932,59 +931,6 @@ void rtas_activate_firmware(void) pr_err("ibm,activate-firmware failed (%i)\n", fwrc); }

-#ifdef CONFIG_PPC_PSERIES -/** - * 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; -} - -#endif /* CONFIG_PPC_PSERIES */ - /** * get_pseries_errorlog() - Find a specific pseries error log in an RTAS * extended event log. diff --git a/arch/powerpc/sysdev/xics/ics-rtas.c b/arch/powerpc/sysdev/xics/ics-rtas.c index 9e7007f9aca5..f8320f8e5bc7 100644 --- a/arch/powerpc/sysdev/xics/ics-rtas.c +++ b/arch/powerpc/sysdev/xics/ics-rtas.c @@ -36,8 +36,8 @@ 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_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq, - server, DEFAULT_PRIORITY); + call_status = rtas_call(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", @@ -46,7 +46,7 @@ static void ics_rtas_unmask_irq(struct irq_data *d) }

/* Now unmask the interrupt (often a no-op) */ - call_status = rtas_call_reentrant(ibm_int_on, 1, 1, NULL, hw_irq); + call_status = rtas_call(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); @@ -68,7 +68,7 @@ static void ics_rtas_mask_real_irq(unsigned int hw_irq) if (hw_irq == XICS_IPI) return;

- call_status = rtas_call_reentrant(ibm_int_off, 1, 1, NULL, hw_irq); + call_status = rtas_call(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); @@ -76,8 +76,8 @@ 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_reentrant(ibm_set_xive, 3, 1, NULL, hw_irq, - xics_default_server, 0xff); + call_status = rtas_call(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); @@ -108,7 +108,7 @@ 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_reentrant(ibm_get_xive, 1, 3, xics_status, hw_irq); + status = rtas_call(ibm_get_xive, 1, 3, xics_status, hw_irq);

if (status) { printk(KERN_ERR "%s: ibm,get-xive irq=%u returns %d\n", @@ -126,8 +126,8 @@ static int ics_rtas_set_affinity(struct irq_data *d, pr_debug("%s: irq %d [hw 0x%x] server: 0x%x\n", __func__, d->irq, hw_irq, irq_server);

- status = rtas_call_reentrant(ibm_set_xive, 3, 1, NULL, - hw_irq, irq_server, xics_status[1]); + status = rtas_call(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", @@ -158,7 +158,7 @@ static int ics_rtas_check(struct ics *ics, unsigned int hw_irq) return -EINVAL;

/* Check if RTAS knows about this interrupt */ - rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, hw_irq); + rc = rtas_call(ibm_get_xive, 1, 3, status, hw_irq); if (rc) return -ENXIO;

@@ -174,7 +174,7 @@ static long ics_rtas_get_server(struct ics *ics, unsigned long vec) { int rc, status[2];

- rc = rtas_call_reentrant(ibm_get_xive, 1, 3, status, vec); + rc = rtas_call(ibm_get_xive, 1, 3, status, vec); if (rc) return -1; return status[0];