From: Mark Rutland <mark.rutland@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Juergen Gross <jgross@suse.com>,
xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, luto@kernel.org,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, Deep Shah <sdeep@vmware.com>,
"VMware, Inc." <pv-drivers@vmware.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf
Date: Thu, 10 Dec 2020 11:10:08 +0000 [thread overview]
Message-ID: <20201210111008.GB88655@C02TD0UTHF1T.local> (raw)
In-Reply-To: <87tusuzu71.fsf@nanos.tec.linutronix.de>
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@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();
> }
>
> /*
next prev parent reply other threads:[~2020-12-10 11:10 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 11:46 [PATCH v2 00/12] x86: major paravirt cleanup Juergen Gross
2020-11-20 11:46 ` [PATCH v2 01/12] x86/xen: use specific Xen pv interrupt entry for MCE Juergen Gross
2020-12-09 21:03 ` Thomas Gleixner
2020-11-20 11:46 ` [PATCH v2 02/12] x86/xen: use specific Xen pv interrupt entry for DF Juergen Gross
2020-12-09 21:03 ` Thomas Gleixner
2020-11-20 11:46 ` [PATCH v2 03/12] x86/pv: switch SWAPGS to ALTERNATIVE Juergen Gross
2020-11-27 11:31 ` Borislav Petkov
2020-12-09 21:07 ` Thomas Gleixner
2020-11-20 11:46 ` [PATCH v2 04/12] x86/xen: drop USERGS_SYSRET64 paravirt call Juergen Gross
2020-12-02 12:32 ` Borislav Petkov
2020-12-02 14:48 ` Jürgen Groß
2020-12-02 17:08 ` Borislav Petkov
2020-11-20 11:46 ` [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf Juergen Gross
2020-11-20 11:59 ` Peter Zijlstra
2020-11-20 12:05 ` Jürgen Groß
2020-11-22 6:55 ` Jürgen Groß
2020-11-22 21:44 ` Andy Lutomirski
2020-11-23 5:21 ` Jürgen Groß
2020-11-23 15:15 ` Andy Lutomirski
2020-12-09 13:27 ` Mark Rutland
2020-12-09 14:02 ` Mark Rutland
2020-12-09 14:05 ` Jürgen Groß
2020-12-09 18:15 ` Mark Rutland
2020-12-09 18:54 ` Thomas Gleixner
2020-12-10 11:10 ` Mark Rutland [this message]
2020-12-10 20:15 ` x86/ioapic: Cleanup the timer_works() irqflags mess Thomas Gleixner
2020-12-11 5:10 ` Jürgen Groß
2020-11-27 2:20 ` [x86] 97e8f0134a: fio.write_iops 8.6% improvement kernel test robot
2020-11-20 11:46 ` [PATCH v2 06/12] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross
2020-11-20 12:01 ` Peter Zijlstra
2020-11-20 12:07 ` Jürgen Groß
2020-11-20 11:46 ` [PATCH v2 07/12] x86: add new features for paravirt patching Juergen Gross
2020-12-08 18:43 ` Borislav Petkov
2020-12-09 7:30 ` Jürgen Groß
2020-12-09 12:03 ` Borislav Petkov
2020-12-09 12:22 ` Jürgen Groß
2020-12-10 17:58 ` Borislav Petkov
2020-11-20 11:46 ` [PATCH v2 08/12] x86/paravirt: remove no longer needed 32-bit pvops cruft Juergen Gross
2020-11-20 12:08 ` Peter Zijlstra
2020-11-20 12:16 ` Jürgen Groß
2020-11-20 16:52 ` Arvind Sankar
2020-11-20 11:46 ` [PATCH v2 09/12] x86/paravirt: switch iret pvops to ALTERNATIVE Juergen Gross
2020-11-20 11:46 ` [PATCH v2 10/12] x86/paravirt: add new macros PVOP_ALT* supporting pvops in ALTERNATIVEs Juergen Gross
2020-11-20 11:46 ` [PATCH v2 11/12] x86/paravirt: switch functions with custom code to ALTERNATIVE Juergen Gross
2020-11-20 15:46 ` kernel test robot
2020-11-25 15:46 ` [x86/paravirt] fd8d46a7a2: kernel-selftests.livepatch.test-callbacks.sh.fail kernel test robot
2020-11-20 11:46 ` [PATCH v2 12/12] x86/paravirt: have only one paravirt patch function Juergen Gross
2020-11-20 14:18 ` kernel test robot
2020-11-20 12:53 ` [PATCH v2 00/12] x86: major paravirt cleanup Peter Zijlstra
2020-11-23 13:43 ` Peter Zijlstra
2020-12-15 11:42 ` Jürgen Groß
2020-12-15 14:18 ` Peter Zijlstra
2020-12-15 14:54 ` Peter Zijlstra
2020-12-15 15:07 ` Jürgen Groß
2020-12-16 0:38 ` Josh Poimboeuf
2020-12-16 8:40 ` Peter Zijlstra
2020-12-16 16:56 ` Josh Poimboeuf
2020-12-16 17:58 ` Peter Zijlstra
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