Messages in this thread Patch in this message | | | From | Thomas Gleixner <> | Subject | [patch V3 33/60] x86/apic/ipi: Tidy up the code and fixup comments | Date | Tue, 1 Aug 2023 12:47:22 +0200 (CEST) |
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Replace the undecodable comment on top of the function, replace the space consuming zero content comments with useful ones and tidy up the implementation to prevent further eye bleed.
Make __default_send_IPI_shortcut() static as it has no other users.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/kernel/apic/ipi.c | 74 ++++++++++++++++++------------------------- arch/x86/kernel/apic/local.h | 2 - 2 files changed, 32 insertions(+), 44 deletions(-)
--- a/arch/x86/kernel/apic/ipi.c +++ b/arch/x86/kernel/apic/ipi.c @@ -108,68 +108,58 @@ static inline void __xapic_wait_icr_idle cpu_relax(); } -void __default_send_IPI_shortcut(unsigned int shortcut, int vector) +/* + * This is safe against interruption because it only writes the lower 32 + * bits of the APIC_ICR register. The destination field is ignored for + * short hand IPIs. + * + * wait_icr_idle() + * write(ICR2, dest) + * NMI + * wait_icr_idle() + * write(ICR) + * wait_icr_idle() + * write(ICR) + * + * This function does not need to disable interrupts as there is no ICR2 + * interaction. The memory write is direct except when the machine is + * affected by the 11AP Pentium erratum, which turns the plain write into + * an XCHG operation. + */ +static void __default_send_IPI_shortcut(unsigned int shortcut, int vector) { /* - * Subtle. In the case of the 'never do double writes' workaround - * we have to lock out interrupts to be safe. As we don't care - * of the value read we use an atomic rmw access to avoid costly - * cli/sti. Otherwise we use an even cheaper single atomic write - * to the APIC. - */ - unsigned int cfg; - - /* - * Wait for idle. + * Wait for the previous ICR command to complete. Use + * safe_apic_wait_icr_idle() for the NMI vector as there have been + * issues where otherwise the system hangs when the panic CPU tries + * to stop the others before launching the kdump kernel. */ if (unlikely(vector == NMI_VECTOR)) safe_apic_wait_icr_idle(); else __xapic_wait_icr_idle(); - /* - * No need to touch the target chip field. Also the destination - * mode is ignored when a shorthand is used. - */ - cfg = __prepare_ICR(shortcut, vector, 0); - - /* - * Send the IPI. The write to APIC_ICR fires this off. - */ - native_apic_mem_write(APIC_ICR, cfg); + /* Destination field (ICR2) and the destination mode are ignored */ + native_apic_mem_write(APIC_ICR, __prepare_ICR(shortcut, vector, 0)); } /* * This is used to send an IPI with no shorthand notation (the destination is * specified in bits 56 to 63 of the ICR). */ -void __default_send_IPI_dest_field(unsigned int mask, int vector, unsigned int dest) +void __default_send_IPI_dest_field(unsigned int dest_mask, int vector, + unsigned int dest_mode) { - unsigned long cfg; - - /* - * Wait for idle. - */ + /* See comment in __default_send_IPI_shortcut() */ if (unlikely(vector == NMI_VECTOR)) safe_apic_wait_icr_idle(); else __xapic_wait_icr_idle(); - /* - * prepare target chip field - */ - cfg = __prepare_ICR2(mask); - native_apic_mem_write(APIC_ICR2, cfg); - - /* - * program the ICR - */ - cfg = __prepare_ICR(0, vector, dest); - - /* - * Send the IPI. The write to APIC_ICR fires this off. - */ - native_apic_mem_write(APIC_ICR, cfg); + /* Set the IPI destination field in the ICR */ + native_apic_mem_write(APIC_ICR2, __prepare_ICR2(dest_mask)); + /* Send it with the proper destination mode */ + native_apic_mem_write(APIC_ICR, __prepare_ICR(0, vector, dest_mode)); } void default_send_IPI_single_phys(int cpu, int vector) --- a/arch/x86/kernel/apic/local.h +++ b/arch/x86/kernel/apic/local.h @@ -44,8 +44,6 @@ static inline unsigned int __prepare_ICR void default_init_apic_ldr(void); -void __default_send_IPI_shortcut(unsigned int shortcut, int vector); - /* * This is used to send an IPI with no shorthand notation (the destination is * specified in bits 56 to 63 of the ICR).
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