Thomas Gleixner
2020-Dec-09 18:54 UTC
[PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf
On Wed, Dec 09 2020 at 18:15, Mark Rutland wrote:> In arch/x86/kernel/apic/io_apic.c's timer_irq_works() we do: > > local_irq_save(flags); > local_irq_enable(); > > [ trigger an IRQ here ] > > local_irq_restore(flags); > > ... and in check_timer() we call that a number of times after either a > local_irq_save() or local_irq_disable(), eventually trailing with a > local_irq_disable() that will balance things up before calling > local_irq_restore(). > > I guess that timer_irq_works() should instead do: > > local_irq_save(flags); > local_irq_enable(); > ... > local_irq_disable(); > local_irq_restore(flags); > > ... assuming we consider that legitimate?Nah. That's old and insane gunk. Thanks, tglx --- arch/x86/kernel/apic/io_apic.c | 22 ++++++---------------- 1 file changed, 6 insertions(+), 16 deletions(-) --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -1618,21 +1618,16 @@ static void __init delay_without_tsc(voi static int __init timer_irq_works(void) { unsigned long t1 = jiffies; - unsigned long flags; if (no_timer_check) return 1; - local_save_flags(flags); local_irq_enable(); - if (boot_cpu_has(X86_FEATURE_TSC)) delay_with_tsc(); else delay_without_tsc(); - local_irq_restore(flags); - /* * Expect a few ticks at least, to be sure some possible * glue logic does not lock up after one or two first @@ -1641,10 +1636,10 @@ static int __init timer_irq_works(void) * least one tick may be lost due to delays. */ - /* jiffies wrap? */ - if (time_after(jiffies, t1 + 4)) - return 1; - return 0; + local_irq_disable(); + + /* Did jiffies advance? */ + return time_after(jiffies, t1 + 4); } /* @@ -2117,13 +2112,12 @@ static inline void __init check_timer(vo struct irq_cfg *cfg = irqd_cfg(irq_data); int node = cpu_to_node(0); int apic1, pin1, apic2, pin2; - unsigned long flags; int no_pin1 = 0; if (!global_clock_event) return; - local_irq_save(flags); + local_irq_disable(); /* * get/set the timer IRQ vector: @@ -2191,7 +2185,6 @@ static inline void __init check_timer(vo goto out; } panic_if_irq_remap("timer doesn't work through Interrupt-remapped IO-APIC"); - local_irq_disable(); clear_IO_APIC_pin(apic1, pin1); if (!no_pin1) apic_printk(APIC_QUIET, KERN_ERR "..MP-BIOS bug: " @@ -2215,7 +2208,6 @@ static inline void __init check_timer(vo /* * Cleanup, just in case ... */ - local_irq_disable(); legacy_pic->mask(0); clear_IO_APIC_pin(apic2, pin2); apic_printk(APIC_QUIET, KERN_INFO "....... failed.\n"); @@ -2232,7 +2224,6 @@ static inline void __init check_timer(vo apic_printk(APIC_QUIET, KERN_INFO "..... works.\n"); goto out; } - local_irq_disable(); legacy_pic->mask(0); apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | cfg->vector); apic_printk(APIC_QUIET, KERN_INFO "..... failed.\n"); @@ -2251,7 +2242,6 @@ static inline void __init check_timer(vo apic_printk(APIC_QUIET, KERN_INFO "..... works.\n"); goto out; } - local_irq_disable(); apic_printk(APIC_QUIET, KERN_INFO "..... failed :(.\n"); if (apic_is_x2apic_enabled()) apic_printk(APIC_QUIET, KERN_INFO @@ -2260,7 +2250,7 @@ static inline void __init check_timer(vo panic("IO-APIC + timer doesn't work! Boot with apic=debug and send a " "report. Then try booting with the 'noapic' option.\n"); out: - local_irq_restore(flags); + local_irq_enable(); } /*
Mark Rutland
2020-Dec-10 11:10 UTC
[PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf
On Wed, Dec 09, 2020 at 07:54:26PM +0100, Thomas Gleixner wrote:> On Wed, Dec 09 2020 at 18:15, Mark Rutland wrote: > > In arch/x86/kernel/apic/io_apic.c's timer_irq_works() we do: > > > > local_irq_save(flags); > > local_irq_enable(); > > > > [ trigger an IRQ here ] > > > > local_irq_restore(flags); > > > > ... and in check_timer() we call that a number of times after either a > > local_irq_save() or local_irq_disable(), eventually trailing with a > > local_irq_disable() that will balance things up before calling > > local_irq_restore().I gave the patchlet below a spin with my debug patch, and it boots cleanly for me under QEMU. If you spin it as a real patch, feel free to add: Tested-by: Mark Rutland <mark.rutland at arm.com> Mark.> --- > arch/x86/kernel/apic/io_apic.c | 22 ++++++---------------- > 1 file changed, 6 insertions(+), 16 deletions(-) > > --- a/arch/x86/kernel/apic/io_apic.c > +++ b/arch/x86/kernel/apic/io_apic.c > @@ -1618,21 +1618,16 @@ static void __init delay_without_tsc(voi > static int __init timer_irq_works(void) > { > unsigned long t1 = jiffies; > - unsigned long flags; > > if (no_timer_check) > return 1; > > - local_save_flags(flags); > local_irq_enable(); > - > if (boot_cpu_has(X86_FEATURE_TSC)) > delay_with_tsc(); > else > delay_without_tsc(); > > - local_irq_restore(flags); > - > /* > * Expect a few ticks at least, to be sure some possible > * glue logic does not lock up after one or two first > @@ -1641,10 +1636,10 @@ static int __init timer_irq_works(void) > * least one tick may be lost due to delays. > */ > > - /* jiffies wrap? */ > - if (time_after(jiffies, t1 + 4)) > - return 1; > - return 0; > + local_irq_disable(); > + > + /* Did jiffies advance? */ > + return time_after(jiffies, t1 + 4); > } > > /* > @@ -2117,13 +2112,12 @@ static inline void __init check_timer(vo > struct irq_cfg *cfg = irqd_cfg(irq_data); > int node = cpu_to_node(0); > int apic1, pin1, apic2, pin2; > - unsigned long flags; > int no_pin1 = 0; > > if (!global_clock_event) > return; > > - local_irq_save(flags); > + local_irq_disable(); > > /* > * get/set the timer IRQ vector: > @@ -2191,7 +2185,6 @@ static inline void __init check_timer(vo > goto out; > } > panic_if_irq_remap("timer doesn't work through Interrupt-remapped IO-APIC"); > - local_irq_disable(); > clear_IO_APIC_pin(apic1, pin1); > if (!no_pin1) > apic_printk(APIC_QUIET, KERN_ERR "..MP-BIOS bug: " > @@ -2215,7 +2208,6 @@ static inline void __init check_timer(vo > /* > * Cleanup, just in case ... > */ > - local_irq_disable(); > legacy_pic->mask(0); > clear_IO_APIC_pin(apic2, pin2); > apic_printk(APIC_QUIET, KERN_INFO "....... failed.\n"); > @@ -2232,7 +2224,6 @@ static inline void __init check_timer(vo > apic_printk(APIC_QUIET, KERN_INFO "..... works.\n"); > goto out; > } > - local_irq_disable(); > legacy_pic->mask(0); > apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | cfg->vector); > apic_printk(APIC_QUIET, KERN_INFO "..... failed.\n"); > @@ -2251,7 +2242,6 @@ static inline void __init check_timer(vo > apic_printk(APIC_QUIET, KERN_INFO "..... works.\n"); > goto out; > } > - local_irq_disable(); > apic_printk(APIC_QUIET, KERN_INFO "..... failed :(.\n"); > if (apic_is_x2apic_enabled()) > apic_printk(APIC_QUIET, KERN_INFO > @@ -2260,7 +2250,7 @@ static inline void __init check_timer(vo > panic("IO-APIC + timer doesn't work! Boot with apic=debug and send a " > "report. Then try booting with the 'noapic' option.\n"); > out: > - local_irq_restore(flags); > + local_irq_enable(); > } > > /*