| Message ID | 1603983387-8738-7-git-send-email-sumit.garg@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Add framework to turn an IPI as NMI | expand |
On Thu, Oct 29, 2020 at 08:26:26PM +0530, Sumit Garg wrote: > Add a new API kgdb_arch_roundup_cpus() for a particular archichecture to > override default kgdb roundup and if it detects at runtime to not support > NMI roundup then it can fallback to default implementation using async > SMP cross-calls. > > Currently such an architecture example is arm64 supporting pseudo NMIs > feature which is only available on platforms which have support for GICv3 > or later version. > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > --- > arch/powerpc/kernel/kgdb.c | 3 ++- > arch/sparc/kernel/smp_64.c | 3 ++- > arch/x86/kernel/kgdb.c | 6 ++++-- > include/linux/kgdb.h | 5 +++-- > kernel/debug/debug_core.c | 10 +++++++++- > 5 files changed, 20 insertions(+), 7 deletions(-) > > diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c > index 4090802..126575d 100644 > --- a/arch/powerpc/kernel/kgdb.c > +++ b/arch/powerpc/kernel/kgdb.c > @@ -125,9 +125,10 @@ static int kgdb_debugger_ipi(struct pt_regs *regs) > } > > #ifdef CONFIG_SMP > -void kgdb_roundup_cpus(void) > +bool kgdb_arch_roundup_cpus(void) > { > smp_send_debugger_break(); > + return true; > } > #endif > > diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c > index e38d8bf..c459c83 100644 > --- a/arch/sparc/kernel/smp_64.c > +++ b/arch/sparc/kernel/smp_64.c > @@ -1014,9 +1014,10 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page) > } > > #ifdef CONFIG_KGDB > -void kgdb_roundup_cpus(void) > +bool kgdb_arch_roundup_cpus(void) > { > smp_cross_call(&xcall_kgdb_capture, 0, 0, 0); > + return true; > } > #endif > > diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c > index ff7878d..1b756d9 100644 > --- a/arch/x86/kernel/kgdb.c > +++ b/arch/x86/kernel/kgdb.c > @@ -404,7 +404,8 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > > #ifdef CONFIG_SMP > /** > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > + * in an architectural specific manner > * > * On SMP systems, we need to get the attention of the other CPUs > * and get them be in a known state. This should do what is needed > @@ -414,9 +415,10 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > * > * On non-SMP systems, this is not called. > */ > -void kgdb_roundup_cpus(void) > +bool kgdb_arch_roundup_cpus(void) > { > apic_send_IPI_allbutself(NMI_VECTOR); > + return true; > } > #endif > > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > index 0d6cf64..f9db5b8 100644 > --- a/include/linux/kgdb.h > +++ b/include/linux/kgdb.h > @@ -200,7 +200,8 @@ kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer, > extern void kgdb_call_nmi_hook(void *ignored); > > /** > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > + * in an architectural specific manner > * > * On SMP systems, we need to get the attention of the other CPUs > * and get them into a known state. This should do what is needed > @@ -210,7 +211,7 @@ extern void kgdb_call_nmi_hook(void *ignored); > * > * On non-SMP systems, this is not called. > */ > -extern void kgdb_roundup_cpus(void); > +extern bool kgdb_arch_roundup_cpus(void); > > /** > * kgdb_arch_set_pc - Generic call back to the program counter > diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c > index 1e75a89..27e401c 100644 > --- a/kernel/debug/debug_core.c > +++ b/kernel/debug/debug_core.c > @@ -241,13 +241,21 @@ void __weak kgdb_call_nmi_hook(void *ignored) > } > NOKPROBE_SYMBOL(kgdb_call_nmi_hook); > > -void __weak kgdb_roundup_cpus(void) > +bool __weak kgdb_arch_roundup_cpus(void) > +{ > + return false; Do we really need to introduce all these boolean return values just to call a bit of library code when one of the architectures wants to fallback to a generic implementation? Why not something more like: void kgdb_smp_call_nmi_hook(void) { /* original weak version of kgdb_roundup_cpus goes here */ } void __weak kgdb_roundup_cpus(void) { kgdb_smp_call_nmi_hook(); } arm64 can now simply call the new library function if a fallback is needed. Note that same question applies to the backtrace changes... Daniel. > +} > + > +static void kgdb_roundup_cpus(void) > { > call_single_data_t *csd; > int this_cpu = raw_smp_processor_id(); > int cpu; > int ret; > > + if (kgdb_arch_roundup_cpus()) > + return; > + > for_each_online_cpu(cpu) { > /* No need to roundup ourselves */ > if (cpu == this_cpu) > -- > 2.7.4 >
On Thu, 29 Oct 2020 at 20:51, Daniel Thompson <daniel.thompson@linaro.org> wrote: > > On Thu, Oct 29, 2020 at 08:26:26PM +0530, Sumit Garg wrote: > > Add a new API kgdb_arch_roundup_cpus() for a particular archichecture to > > override default kgdb roundup and if it detects at runtime to not support > > NMI roundup then it can fallback to default implementation using async > > SMP cross-calls. > > > > Currently such an architecture example is arm64 supporting pseudo NMIs > > feature which is only available on platforms which have support for GICv3 > > or later version. > > > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > --- > > arch/powerpc/kernel/kgdb.c | 3 ++- > > arch/sparc/kernel/smp_64.c | 3 ++- > > arch/x86/kernel/kgdb.c | 6 ++++-- > > include/linux/kgdb.h | 5 +++-- > > kernel/debug/debug_core.c | 10 +++++++++- > > 5 files changed, 20 insertions(+), 7 deletions(-) > > > > diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c > > index 4090802..126575d 100644 > > --- a/arch/powerpc/kernel/kgdb.c > > +++ b/arch/powerpc/kernel/kgdb.c > > @@ -125,9 +125,10 @@ static int kgdb_debugger_ipi(struct pt_regs *regs) > > } > > > > #ifdef CONFIG_SMP > > -void kgdb_roundup_cpus(void) > > +bool kgdb_arch_roundup_cpus(void) > > { > > smp_send_debugger_break(); > > + return true; > > } > > #endif > > > > diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c > > index e38d8bf..c459c83 100644 > > --- a/arch/sparc/kernel/smp_64.c > > +++ b/arch/sparc/kernel/smp_64.c > > @@ -1014,9 +1014,10 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page) > > } > > > > #ifdef CONFIG_KGDB > > -void kgdb_roundup_cpus(void) > > +bool kgdb_arch_roundup_cpus(void) > > { > > smp_cross_call(&xcall_kgdb_capture, 0, 0, 0); > > + return true; > > } > > #endif > > > > diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c > > index ff7878d..1b756d9 100644 > > --- a/arch/x86/kernel/kgdb.c > > +++ b/arch/x86/kernel/kgdb.c > > @@ -404,7 +404,8 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > > > > #ifdef CONFIG_SMP > > /** > > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > > + * in an architectural specific manner > > * > > * On SMP systems, we need to get the attention of the other CPUs > > * and get them be in a known state. This should do what is needed > > @@ -414,9 +415,10 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > > * > > * On non-SMP systems, this is not called. > > */ > > -void kgdb_roundup_cpus(void) > > +bool kgdb_arch_roundup_cpus(void) > > { > > apic_send_IPI_allbutself(NMI_VECTOR); > > + return true; > > } > > #endif > > > > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > > index 0d6cf64..f9db5b8 100644 > > --- a/include/linux/kgdb.h > > +++ b/include/linux/kgdb.h > > @@ -200,7 +200,8 @@ kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer, > > extern void kgdb_call_nmi_hook(void *ignored); > > > > /** > > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > > + * in an architectural specific manner > > * > > * On SMP systems, we need to get the attention of the other CPUs > > * and get them into a known state. This should do what is needed > > @@ -210,7 +211,7 @@ extern void kgdb_call_nmi_hook(void *ignored); > > * > > * On non-SMP systems, this is not called. > > */ > > -extern void kgdb_roundup_cpus(void); > > +extern bool kgdb_arch_roundup_cpus(void); > > > > /** > > * kgdb_arch_set_pc - Generic call back to the program counter > > diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c > > index 1e75a89..27e401c 100644 > > --- a/kernel/debug/debug_core.c > > +++ b/kernel/debug/debug_core.c > > @@ -241,13 +241,21 @@ void __weak kgdb_call_nmi_hook(void *ignored) > > } > > NOKPROBE_SYMBOL(kgdb_call_nmi_hook); > > > > -void __weak kgdb_roundup_cpus(void) > > +bool __weak kgdb_arch_roundup_cpus(void) > > +{ > > + return false; > > Do we really need to introduce all these boolean return values just to > call a bit of library code when one of the architectures wants to > fallback to a generic implementation? > > Why not something more like: > > void kgdb_smp_call_nmi_hook(void) > { > /* original weak version of kgdb_roundup_cpus goes here */ > } > > void __weak kgdb_roundup_cpus(void) > { > kgdb_smp_call_nmi_hook(); > } > > arm64 can now simply call the new library function if a fallback is needed. > Makes sense, I will use this approach instead. > Note that same question applies to the backtrace changes... In case of backtrace, there are already multiple APIs wrapping arch_trigger_cpumask_backtrace() as follows: - trigger_all_cpu_backtrace() - trigger_allbutself_cpu_backtrace() - trigger_cpumask_backtrace() - trigger_single_cpu_backtrace() And each of them already return a boolean and have corresponding different fallback mechanisms. So we can't have a common fallback API from arch specific code and instead need to extend that boolean return to arch specific code that is implemented as part of patch #4. If you do have any better ideas then do let me know. -Sumit > > > Daniel. > > > > +} > > + > > +static void kgdb_roundup_cpus(void) > > { > > call_single_data_t *csd; > > int this_cpu = raw_smp_processor_id(); > > int cpu; > > int ret; > > > > + if (kgdb_arch_roundup_cpus()) > > + return; > > + > > for_each_online_cpu(cpu) { > > /* No need to roundup ourselves */ > > if (cpu == this_cpu) > > -- > > 2.7.4 > >
On Mon, Nov 02, 2020 at 11:48:53AM +0530, Sumit Garg wrote: > On Thu, 29 Oct 2020 at 20:51, Daniel Thompson > <daniel.thompson@linaro.org> wrote: > > > > On Thu, Oct 29, 2020 at 08:26:26PM +0530, Sumit Garg wrote: > > > Add a new API kgdb_arch_roundup_cpus() for a particular archichecture to > > > override default kgdb roundup and if it detects at runtime to not support > > > NMI roundup then it can fallback to default implementation using async > > > SMP cross-calls. > > > > > > Currently such an architecture example is arm64 supporting pseudo NMIs > > > feature which is only available on platforms which have support for GICv3 > > > or later version. > > > > > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > > --- > > > arch/powerpc/kernel/kgdb.c | 3 ++- > > > arch/sparc/kernel/smp_64.c | 3 ++- > > > arch/x86/kernel/kgdb.c | 6 ++++-- > > > include/linux/kgdb.h | 5 +++-- > > > kernel/debug/debug_core.c | 10 +++++++++- > > > 5 files changed, 20 insertions(+), 7 deletions(-) > > > > > > diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c > > > index 4090802..126575d 100644 > > > --- a/arch/powerpc/kernel/kgdb.c > > > +++ b/arch/powerpc/kernel/kgdb.c > > > @@ -125,9 +125,10 @@ static int kgdb_debugger_ipi(struct pt_regs *regs) > > > } > > > > > > #ifdef CONFIG_SMP > > > -void kgdb_roundup_cpus(void) > > > +bool kgdb_arch_roundup_cpus(void) > > > { > > > smp_send_debugger_break(); > > > + return true; > > > } > > > #endif > > > > > > diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c > > > index e38d8bf..c459c83 100644 > > > --- a/arch/sparc/kernel/smp_64.c > > > +++ b/arch/sparc/kernel/smp_64.c > > > @@ -1014,9 +1014,10 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page) > > > } > > > > > > #ifdef CONFIG_KGDB > > > -void kgdb_roundup_cpus(void) > > > +bool kgdb_arch_roundup_cpus(void) > > > { > > > smp_cross_call(&xcall_kgdb_capture, 0, 0, 0); > > > + return true; > > > } > > > #endif > > > > > > diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c > > > index ff7878d..1b756d9 100644 > > > --- a/arch/x86/kernel/kgdb.c > > > +++ b/arch/x86/kernel/kgdb.c > > > @@ -404,7 +404,8 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > > > > > > #ifdef CONFIG_SMP > > > /** > > > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > > > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > > > + * in an architectural specific manner > > > * > > > * On SMP systems, we need to get the attention of the other CPUs > > > * and get them be in a known state. This should do what is needed > > > @@ -414,9 +415,10 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > > > * > > > * On non-SMP systems, this is not called. > > > */ > > > -void kgdb_roundup_cpus(void) > > > +bool kgdb_arch_roundup_cpus(void) > > > { > > > apic_send_IPI_allbutself(NMI_VECTOR); > > > + return true; > > > } > > > #endif > > > > > > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > > > index 0d6cf64..f9db5b8 100644 > > > --- a/include/linux/kgdb.h > > > +++ b/include/linux/kgdb.h > > > @@ -200,7 +200,8 @@ kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer, > > > extern void kgdb_call_nmi_hook(void *ignored); > > > > > > /** > > > - * kgdb_roundup_cpus - Get other CPUs into a holding pattern > > > + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern > > > + * in an architectural specific manner > > > * > > > * On SMP systems, we need to get the attention of the other CPUs > > > * and get them into a known state. This should do what is needed > > > @@ -210,7 +211,7 @@ extern void kgdb_call_nmi_hook(void *ignored); > > > * > > > * On non-SMP systems, this is not called. > > > */ > > > -extern void kgdb_roundup_cpus(void); > > > +extern bool kgdb_arch_roundup_cpus(void); > > > > > > /** > > > * kgdb_arch_set_pc - Generic call back to the program counter > > > diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c > > > index 1e75a89..27e401c 100644 > > > --- a/kernel/debug/debug_core.c > > > +++ b/kernel/debug/debug_core.c > > > @@ -241,13 +241,21 @@ void __weak kgdb_call_nmi_hook(void *ignored) > > > } > > > NOKPROBE_SYMBOL(kgdb_call_nmi_hook); > > > > > > -void __weak kgdb_roundup_cpus(void) > > > +bool __weak kgdb_arch_roundup_cpus(void) > > > +{ > > > + return false; > > > > Do we really need to introduce all these boolean return values just to > > call a bit of library code when one of the architectures wants to > > fallback to a generic implementation? > > > > Why not something more like: > > > > void kgdb_smp_call_nmi_hook(void) > > { > > /* original weak version of kgdb_roundup_cpus goes here */ > > } > > > > void __weak kgdb_roundup_cpus(void) > > { > > kgdb_smp_call_nmi_hook(); > > } > > > > arm64 can now simply call the new library function if a fallback is needed. > > > > Makes sense, I will use this approach instead. > > > Note that same question applies to the backtrace changes... > > In case of backtrace, there are already multiple APIs wrapping > arch_trigger_cpumask_backtrace() as follows: > > - trigger_all_cpu_backtrace() > - trigger_allbutself_cpu_backtrace() > - trigger_cpumask_backtrace() > - trigger_single_cpu_backtrace() > > And each of them already return a boolean and have corresponding > different fallback mechanisms. So we can't have a common fallback API > from arch specific code and instead need to extend that boolean return > to arch specific code that is implemented as part of patch #4. Understood. Thanks. Daniel.
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c index 4090802..126575d 100644 --- a/arch/powerpc/kernel/kgdb.c +++ b/arch/powerpc/kernel/kgdb.c @@ -125,9 +125,10 @@ static int kgdb_debugger_ipi(struct pt_regs *regs) } #ifdef CONFIG_SMP -void kgdb_roundup_cpus(void) +bool kgdb_arch_roundup_cpus(void) { smp_send_debugger_break(); + return true; } #endif diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c index e38d8bf..c459c83 100644 --- a/arch/sparc/kernel/smp_64.c +++ b/arch/sparc/kernel/smp_64.c @@ -1014,9 +1014,10 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page) } #ifdef CONFIG_KGDB -void kgdb_roundup_cpus(void) +bool kgdb_arch_roundup_cpus(void) { smp_cross_call(&xcall_kgdb_capture, 0, 0, 0); + return true; } #endif diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c index ff7878d..1b756d9 100644 --- a/arch/x86/kernel/kgdb.c +++ b/arch/x86/kernel/kgdb.c @@ -404,7 +404,8 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) #ifdef CONFIG_SMP /** - * kgdb_roundup_cpus - Get other CPUs into a holding pattern + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern + * in an architectural specific manner * * On SMP systems, we need to get the attention of the other CPUs * and get them be in a known state. This should do what is needed @@ -414,9 +415,10 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) * * On non-SMP systems, this is not called. */ -void kgdb_roundup_cpus(void) +bool kgdb_arch_roundup_cpus(void) { apic_send_IPI_allbutself(NMI_VECTOR); + return true; } #endif diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index 0d6cf64..f9db5b8 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -200,7 +200,8 @@ kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer, extern void kgdb_call_nmi_hook(void *ignored); /** - * kgdb_roundup_cpus - Get other CPUs into a holding pattern + * kgdb_arch_roundup_cpus - Get other CPUs into a holding pattern + * in an architectural specific manner * * On SMP systems, we need to get the attention of the other CPUs * and get them into a known state. This should do what is needed @@ -210,7 +211,7 @@ extern void kgdb_call_nmi_hook(void *ignored); * * On non-SMP systems, this is not called. */ -extern void kgdb_roundup_cpus(void); +extern bool kgdb_arch_roundup_cpus(void); /** * kgdb_arch_set_pc - Generic call back to the program counter diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 1e75a89..27e401c 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -241,13 +241,21 @@ void __weak kgdb_call_nmi_hook(void *ignored) } NOKPROBE_SYMBOL(kgdb_call_nmi_hook); -void __weak kgdb_roundup_cpus(void) +bool __weak kgdb_arch_roundup_cpus(void) +{ + return false; +} + +static void kgdb_roundup_cpus(void) { call_single_data_t *csd; int this_cpu = raw_smp_processor_id(); int cpu; int ret; + if (kgdb_arch_roundup_cpus()) + return; + for_each_online_cpu(cpu) { /* No need to roundup ourselves */ if (cpu == this_cpu)
Add a new API kgdb_arch_roundup_cpus() for a particular archichecture to override default kgdb roundup and if it detects at runtime to not support NMI roundup then it can fallback to default implementation using async SMP cross-calls. Currently such an architecture example is arm64 supporting pseudo NMIs feature which is only available on platforms which have support for GICv3 or later version. Signed-off-by: Sumit Garg <sumit.garg@linaro.org> --- arch/powerpc/kernel/kgdb.c | 3 ++- arch/sparc/kernel/smp_64.c | 3 ++- arch/x86/kernel/kgdb.c | 6 ++++-- include/linux/kgdb.h | 5 +++-- kernel/debug/debug_core.c | 10 +++++++++- 5 files changed, 20 insertions(+), 7 deletions(-)