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powerpc/pseries: Fix xive=off command line

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On POWER9, if the hypervisor supports XIVE exploitation mode, the
guest OS will unconditionally requests for the XIVE interrupt mode
even if XIVE was deactivated with the kernel command line xive=off.
Later on, when the spapr XIVE init code handles xive=off, it disables
XIVE and tries to fall back on the legacy mode XICS.

This discrepency causes a kernel panic because the hypervisor is
configured to provide the XIVE interrupt mode to the guest :

  kernel BUG at arch/powerpc/sysdev/xics/xics-common.c:135!
  ...
  NIP xics_smp_probe+0x38/0x98
  LR  xics_smp_probe+0x2c/0x98
  Call Trace:
    xics_smp_probe+0x2c/0x98 (unreliable)
    pSeries_smp_probe+0x40/0xa0
    smp_prepare_cpus+0x62c/0x6ec
    kernel_init_freeable+0x148/0x448
    kernel_init+0x2c/0x148
    ret_from_kernel_thread+0x5c/0x68

Look for xive=off during prom_init and don't ask for XIVE in this
case. One exception though: if the host only supports XIVE, we still
want to boot so we ignore xive=off.

Similarly, have the spapr XIVE init code to looking at the interrupt
mode negotiated during CAS, and ignore xive=off if the hypervisor only
supports XIVE.

Fixes: eac1e731b5 ("powerpc/xive: guest exploitation of the XIVE interrupt controller")
Cc: stable@vger.kernel.org # v4.20
Reported-by: Pavithra R. Prakash <pavrampu@in.ibm.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Greg Kurz 2019-05-15 12:05:01 +02:00 committed by Michael Ellerman
parent 02c5f53949
commit a3bf9fbdad
2 changed files with 66 additions and 2 deletions
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16
arch/powerpc/kernel/prom_init.c
View file

@ -172,6 +172,7 @@ static unsigned long __prombss prom_tce_alloc_end;
#ifdef CONFIG_PPC_PSERIES
static bool __prombss prom_radix_disable;
static bool __prombss prom_xive_disable;
#endif
struct platform_support {
@ -808,6 +809,12 @@ static void __init early_cmdline_parse(void)
}
if (prom_radix_disable)
prom_debug("Radix disabled from cmdline\n");
opt = prom_strstr(prom_cmd_line, "xive=off");
if (opt) {
prom_xive_disable = true;
prom_debug("XIVE disabled from cmdline\n");
}
#endif /* CONFIG_PPC_PSERIES */
}
@ -1216,10 +1223,17 @@ static void __init prom_parse_xive_model(u8 val,
switch (val) {
case OV5_FEAT(OV5_XIVE_EITHER): /* Either Available */
prom_debug("XIVE - either mode supported\n");
support->xive = true;
support->xive = !prom_xive_disable;
break;
case OV5_FEAT(OV5_XIVE_EXPLOIT): /* Only Exploitation mode */
prom_debug("XIVE - exploitation mode supported\n");
if (prom_xive_disable) {
/*
* If we __have__ to do XIVE, we're better off ignoring
* the command line rather than not booting.
*/
prom_printf("WARNING: Ignoring cmdline option xive=off\n");
}
support->xive = true;
break;
case OV5_FEAT(OV5_XIVE_LEGACY): /* Only Legacy mode */

52
arch/powerpc/sysdev/xive/spapr.c
View file

@ -20,6 +20,7 @@
#include <linux/cpumask.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/libfdt.h>
#include <asm/prom.h>
#include <asm/io.h>
@ -663,6 +664,55 @@ static bool xive_get_max_prio(u8 *max_prio)
return true;
}
static const u8 *get_vec5_feature(unsigned int index)
{
unsigned long root, chosen;
int size;
const u8 *vec5;
root = of_get_flat_dt_root();
chosen = of_get_flat_dt_subnode_by_name(root, "chosen");
if (chosen == -FDT_ERR_NOTFOUND)
return NULL;
vec5 = of_get_flat_dt_prop(chosen, "ibm,architecture-vec-5", &size);
if (!vec5)
return NULL;
if (size <= index)
return NULL;
return vec5 + index;
}
static bool xive_spapr_disabled(void)
{
const u8 *vec5_xive;
vec5_xive = get_vec5_feature(OV5_INDX(OV5_XIVE_SUPPORT));
if (vec5_xive) {
u8 val;
val = *vec5_xive & OV5_FEAT(OV5_XIVE_SUPPORT);
switch (val) {
case OV5_FEAT(OV5_XIVE_EITHER):
case OV5_FEAT(OV5_XIVE_LEGACY):
break;
case OV5_FEAT(OV5_XIVE_EXPLOIT):
/* Hypervisor only supports XIVE */
if (xive_cmdline_disabled)
pr_warn("WARNING: Ignoring cmdline option xive=off\n");
return false;
default:
pr_warn("%s: Unknown xive support option: 0x%x\n",
__func__, val);
break;
}
}
return xive_cmdline_disabled;
}
bool __init xive_spapr_init(void)
{
struct device_node *np;
@ -675,7 +725,7 @@ bool __init xive_spapr_init(void)
const __be32 *reg;
int i;
if (xive_cmdline_disabled)
if (xive_spapr_disabled())
return false;
pr_devel("%s()\n", __func__);