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(); > } > > /*
Mark tripped over the creative irqflags handling in the IO-APIC timer
delivery check which ends up doing:
local_irq_save(flags);
local_irq_enable();
local_irq_restore(flags);
which triggered a new consistency check he's working on required for
replacing the POPF based restore with a conditional STI.
That code is a historical mess and none of this is needed. Make it
straightforward use local_irq_disable()/enable() as that's all what is
required. It is invoked from interrupt enabled code nowadays.
Reported-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Tested-by: Mark Rutland <mark.rutland at arm.com>
---
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();
}
/*