# \[PATCH\] powerpc/powernv: Return secondary CPUs to firmware on kexec - Subsystems: LINUX FOR POWERPC (32-BIT AND 64-BIT), THE REST - Maintainers: Madhavan Srinivasan, Linus Torvalds - List: linuxppc-dev - 3 messages, 2 authors - Page: https://ratatoskr.run/linuxppc-dev/2013/08/9475864/t ## \[PATCH\] powerpc/powernv: Return secondary CPUs to firmware on kexec - From: Benjamin Herrenschmidt \ - Date: 2013-08-16 00:05:52 - Message: https://ratatoskr.run/linuxppc-dev/2013/08/9475864.md ```text With OPAL v3 we can return secondary CPUs to firmware on kexec. This allows firmware to do various cleanups making things generally more reliable, and will enable the "new" kernel to call OPAL to perform some reconfiguration tasks early on that can only be done while all the CPUs are in firmware. Signed-off-by: Benjamin Herrenschmidt diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index d4459bf..b59a1da 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -31,6 +31,7 @@ #include #include #include +#include #include "powernv.h" @@ -143,6 +144,16 @@ static void pnv_shutdown(void) static void pnv_kexec_cpu_down(int crash_shutdown, int secondary) { xics_kexec_teardown_cpu(secondary); + + /* Return secondary CPUs to firmware on OPAL v3 */ + if (firmware_has_feature(FW_FEATURE_OPALv3) && secondary) { + mb(); + get_paca()->kexec_state = KEXEC_STATE_REAL_MODE; + mb(); + + /* Return the CPU to OPAL */ + opal_return_cpu(); + } } #endif /* CONFIG_KEXEC */ ``` ## Re: \[PATCH\] powerpc/powernv: Return secondary CPUs to firmware on kexec - From: Michael Neuling \ - Date: 2013-08-16 01:16:19 - Message: https://ratatoskr.run/linuxppc-dev/2013/08/9475866.md ```text > With OPAL v3 we can return secondary CPUs to firmware on kexec. This > allows firmware to do various cleanups making things generally more > reliable, and will enable the "new" kernel to call OPAL to perform > some reconfiguration tasks early on that can only be done while > all the CPUs are in firmware. Dumb question, but isn't the point of kexec to avoid fw interactions like this? Mikey > Signed-off-by: Benjamin Herrenschmidt > > diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c > index d4459bf..b59a1da 100644 > --- a/arch/powerpc/platforms/powernv/setup.c > +++ b/arch/powerpc/platforms/powernv/setup.c > @@ -31,6 +31,7 @@ > #include > #include > #include > +#include > > #include "powernv.h" > > @@ -143,6 +144,16 @@ static void pnv_shutdown(void) > static void pnv_kexec_cpu_down(int crash_shutdown, int secondary) > { > xics_kexec_teardown_cpu(secondary); > + > + /* Return secondary CPUs to firmware on OPAL v3 */ > + if (firmware_has_feature(FW_FEATURE_OPALv3) && secondary) { > + mb(); > + get_paca()->kexec_state = KEXEC_STATE_REAL_MODE; > + mb(); > + > + /* Return the CPU to OPAL */ > + opal_return_cpu(); > + } > } > #endif /* CONFIG_KEXEC */ > > > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev > ``` ## Re: \[PATCH\] powerpc/powernv: Return secondary CPUs to firmware on kexec - From: Benjamin Herrenschmidt \ - Date: 2013-08-16 03:34:43 - Message: https://ratatoskr.run/linuxppc-dev/2013/08/9475868.md ```text On Fri, 2013-08-16 at 11:16 +1000, Michael Neuling wrote: > > > With OPAL v3 we can return secondary CPUs to firmware on kexec. This > > allows firmware to do various cleanups making things generally more > > reliable, and will enable the "new" kernel to call OPAL to perform > > some reconfiguration tasks early on that can only be done while > > all the CPUs are in firmware. > > Dumb question, but isn't the point of kexec to avoid fw interactions > like this? The point of kexec is to avoid rebooting :-) Sending secondaries back to the OPAL internal spin loop doesn't take a noticeable amount of time. We could avoid doing it and solve the problem of needing all CPUs in firmware for "reconfig" differently however. We could have the "target" kernel code take them out of kexec into a special path that goes back into the fw ... I chose the kexec solution because it was simpler and less code :-) Cheers, Ben. > Mikey > > > > Signed-off-by: Benjamin Herrenschmidt > > > > diff --git a/arch/powerpc/platforms/powernv/setup.c > b/arch/powerpc/platforms/powernv/setup.c > > index d4459bf..b59a1da 100644 > > --- a/arch/powerpc/platforms/powernv/setup.c > > +++ b/arch/powerpc/platforms/powernv/setup.c > > @@ -31,6 +31,7 @@ > > #include > > #include > > #include > > +#include > > > > #include "powernv.h" > > > > @@ -143,6 +144,16 @@ static void pnv_shutdown(void) > > static void pnv_kexec_cpu_down(int crash_shutdown, int secondary) > > { > > xics_kexec_teardown_cpu(secondary); > > + > > + /* Return secondary CPUs to firmware on OPAL v3 */ > > + if (firmware_has_feature(FW_FEATURE_OPALv3) && secondary) { > > + mb(); > > + get_paca()->kexec_state = KEXEC_STATE_REAL_MODE; > > + mb(); > > + > > + /* Return the CPU to OPAL */ > > + opal_return_cpu(); > > + } > > } > > #endif /* CONFIG_KEXEC */ > > > > > > > > _______________________________________________ > > Linuxppc-dev mailing list > > Linuxppc-dev@lists.ozlabs.org > > https://lists.ozlabs.org/listinfo/linuxppc-dev > > > > ```