* [PATCH] x86/SMP: CPU0's scratch mask is needed earlier
@ 2016-12-19 9:45 Jan Beulich
2016-12-19 10:38 ` Andrew Cooper
0 siblings, 1 reply; 2+ messages in thread
From: Jan Beulich @ 2016-12-19 9:45 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper
[-- Attachment #1: Type: text/plain, Size: 2386 bytes --]
When putting together commit 3b61726458 ("x86: introduce and use
scratch CPU mask") I failed to remember that AMD IOMMU setups needs the
scratch mask prior to smp_prepare_cpus() having run. Use a static mask
for the boot CPU instead.
Note that the definition of scratch_cpu0mask could also be put inside a
"NR_CPUS > 2 * BITS_PER_LONG" conditional, but it seems preferable to
me to carry the extra variable in all cases and avoid the #ifdef-ary.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
I'm not particularly happy about the remaining #ifdef, but I don't see
a way to avoid it.
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -57,6 +57,7 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_mask);
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, scratch_cpumask);
+static cpumask_t scratch_cpu0mask;
cpumask_t cpu_online_map __read_mostly;
EXPORT_SYMBOL(cpu_online_map);
@@ -648,7 +649,8 @@ static void cpu_smpboot_free(unsigned in
free_cpumask_var(per_cpu(cpu_sibling_mask, cpu));
free_cpumask_var(per_cpu(cpu_core_mask, cpu));
- free_cpumask_var(per_cpu(scratch_cpumask, cpu));
+ if ( per_cpu(scratch_cpumask, cpu) != &scratch_cpu0mask )
+ free_cpumask_var(per_cpu(scratch_cpumask, cpu));
if ( per_cpu(stubs.addr, cpu) )
{
@@ -795,8 +797,7 @@ void __init smp_prepare_cpus(unsigned in
panic("No memory for socket CPU siblings map");
if ( !zalloc_cpumask_var(&per_cpu(cpu_sibling_mask, 0)) ||
- !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) ||
- !alloc_cpumask_var(&per_cpu(scratch_cpumask, 0)) )
+ !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) )
panic("No memory for boot CPU sibling/core maps");
set_cpu_sibling_map(0);
@@ -850,8 +851,13 @@ void __init smp_prepare_cpus(unsigned in
void __init smp_prepare_boot_cpu(void)
{
- cpumask_set_cpu(smp_processor_id(), &cpu_online_map);
- cpumask_set_cpu(smp_processor_id(), &cpu_present_map);
+ unsigned int cpu = smp_processor_id();
+
+ cpumask_set_cpu(cpu, &cpu_online_map);
+ cpumask_set_cpu(cpu, &cpu_present_map);
+#if NR_CPUS > 2 * BITS_PER_LONG
+ per_cpu(scratch_cpumask, cpu) = &scratch_cpu0mask;
+#endif
}
static void
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x86/SMP: CPU0's scratch mask is needed earlier
When putting together commit 3b61726458 ("x86: introduce and use
scratch CPU mask") I failed to remember that AMD IOMMU setups needs the
scratch mask prior to smp_prepare_cpus() having run. Use a static mask
for the boot CPU instead.
Note that the definition of scratch_cpu0mask could also be put inside a
"NR_CPUS > 2 * BITS_PER_LONG" conditional, but it seems preferable to
me to carry the extra variable in all cases and avoid the #ifdef-ary.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
I'm not particularly happy about the remaining #ifdef, but I don't see
a way to avoid it.
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -57,6 +57,7 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_mask);
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, scratch_cpumask);
+static cpumask_t scratch_cpu0mask;
cpumask_t cpu_online_map __read_mostly;
EXPORT_SYMBOL(cpu_online_map);
@@ -648,7 +649,8 @@ static void cpu_smpboot_free(unsigned in
free_cpumask_var(per_cpu(cpu_sibling_mask, cpu));
free_cpumask_var(per_cpu(cpu_core_mask, cpu));
- free_cpumask_var(per_cpu(scratch_cpumask, cpu));
+ if ( per_cpu(scratch_cpumask, cpu) != &scratch_cpu0mask )
+ free_cpumask_var(per_cpu(scratch_cpumask, cpu));
if ( per_cpu(stubs.addr, cpu) )
{
@@ -795,8 +797,7 @@ void __init smp_prepare_cpus(unsigned in
panic("No memory for socket CPU siblings map");
if ( !zalloc_cpumask_var(&per_cpu(cpu_sibling_mask, 0)) ||
- !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) ||
- !alloc_cpumask_var(&per_cpu(scratch_cpumask, 0)) )
+ !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) )
panic("No memory for boot CPU sibling/core maps");
set_cpu_sibling_map(0);
@@ -850,8 +851,13 @@ void __init smp_prepare_cpus(unsigned in
void __init smp_prepare_boot_cpu(void)
{
- cpumask_set_cpu(smp_processor_id(), &cpu_online_map);
- cpumask_set_cpu(smp_processor_id(), &cpu_present_map);
+ unsigned int cpu = smp_processor_id();
+
+ cpumask_set_cpu(cpu, &cpu_online_map);
+ cpumask_set_cpu(cpu, &cpu_present_map);
+#if NR_CPUS > 2 * BITS_PER_LONG
+ per_cpu(scratch_cpumask, cpu) = &scratch_cpu0mask;
+#endif
}
static void
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^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH] x86/SMP: CPU0's scratch mask is needed earlier
2016-12-19 9:45 [PATCH] x86/SMP: CPU0's scratch mask is needed earlier Jan Beulich
@ 2016-12-19 10:38 ` Andrew Cooper
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Cooper @ 2016-12-19 10:38 UTC (permalink / raw)
To: Jan Beulich, xen-devel
On 19/12/16 09:45, Jan Beulich wrote:
> When putting together commit 3b61726458 ("x86: introduce and use
> scratch CPU mask") I failed to remember that AMD IOMMU setups needs the
> scratch mask prior to smp_prepare_cpus() having run. Use a static mask
> for the boot CPU instead.
>
> Note that the definition of scratch_cpu0mask could also be put inside a
> "NR_CPUS > 2 * BITS_PER_LONG" conditional, but it seems preferable to
> me to carry the extra variable in all cases and avoid the #ifdef-ary.
>
> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> I'm not particularly happy about the remaining #ifdef, but I don't see
> a way to avoid it.
Nor me.
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Lets unblock staging while considering if there is a better way of doing
this.
~Andrew
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