[PATCH 5.19 16/33] Revert "powerpc/rtas: Implement reentrant rtas call"

Greg Kroah-Hartman
2022-10-13T18:06:25Z

From: Nathan Lynch <nathanl@linux.ibm.com>

commit f88aabad33ea22be2ce1c60d8901942e4e2a9edb upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/include/asm/paca.h | 1
arch/powerpc/include/asm/rtas.h | 1
arch/powerpc/kernel/paca.c | 32 ---------------------
arch/powerpc/kernel/rtas.c | 54 ------------------------------------
arch/powerpc/sysdev/xics/ics-rtas.c | 22 +++++++-------
5 files changed, 11 insertions(+), 99 deletions(-)

--- 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 */

--- 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);
--- 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_sl
}
#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_
/* 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 */
@@ -308,9 +279,6 @@ void __init allocate_paca(int cpu)
#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);
}

--- 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.
--- 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 i

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 i
}

/* 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(unsig
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(unsig
}

/* 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
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
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 *ic
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 i
{
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];