On 06/10/2015 22:33, Radim Krčmář wrote:
> 2015-08-15 02:00+0200, Paolo Bonzini:
>> On 14/08/2015 10:38, Radim Krčmář wrote:
>>>> How do you reproduce the bug?
>>> I run rhel4 (2.6.9) kernel on 2 VCPUs and frequently alternate
>>> smp_affinity of "timer". The bug is hit within seconds.
>>
>> Nice, I'll try to make a unit test for it on the plane. :)
>
> (Time on planes is best spent by sleeping ;])
That's what I ended up doing. :)
> What do you think about the series?
I had just a few small comments. I had all but forgotten it, sorry.
The unit test makes the bug clear, thanks. What's the issue with
handle_irq?
Paolo
> I made a prototype kvm-unit-test ...
> (Reproduces with APICv or split irqchip builds.)
> ---8<---
> x86: test IO-APIC dest_id modification before
>
> Regression test for kvm commit $TODO.
> Run with '-smp 2'.
>
> I had problems with handle_irq so this version uses asm workaround;
> will fix that in final version. Initialization also presumes that
> everything will work as it did on my machines :)
> ---
> x86/ioapic.c | 47 +++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/x86/ioapic.c b/x86/ioapic.c
> index 1fe1ccc9eadd..55f8eea03496 100644
> --- a/x86/ioapic.c
> +++ b/x86/ioapic.c
> @@ -4,21 +4,27 @@
> #include "smp.h"
> #include "desc.h"
> #include "isr.h"
> +#include "io.h"
>
> #define EDGE_TRIGGERED 0
> #define LEVEL_TRIGGERED 1
>
> -static void set_ioapic_redir(unsigned line, unsigned vec, unsigned trig_mode)
> +static void __set_ioapic_redir(unsigned line, u8 vec, bool trig_mode, u8 dest_id)
> {
> ioapic_redir_entry_t e = {
> .vector = vec,
> - .delivery_mode = 0,
> .trig_mode = trig_mode,
> + .dest_id = dest_id,
> };
>
> ioapic_write_redir(line, e);
> }
>
> +static void set_ioapic_redir(unsigned line, unsigned vec, unsigned trig_mode)
> +{
> + __set_ioapic_redir(line, vec, trig_mode, 0);
> +}
> +
> static void set_irq_line(unsigned line, int val)
> {
> asm volatile("out %0, %1" : : "a"((u8)val), "d"((u16)(0x2000 + line)));
> @@ -298,6 +304,41 @@ static void test_ioapic_level_retrigger_mask(void)
> set_mask(0x0e, false);
> }
>
> +static volatile int pit_working = -1;
> +
> +static void __attribute__((used)) pit_isr_fn(void)
> +{
> + if (!pit_working++);
> + __set_ioapic_redir(0x2, 0x84, EDGE_TRIGGERED, 1);
> + eoi();
> +}
> +
> +void pit_isr(void);
> +asm (
> + "pit_isr: \n"
> + " call pit_isr_fn \n"
> +#ifndef __x86_64__
> + " iret"
> +#else
> + " iretq"
> +#endif
> + );
> +
> +static void test_ioapic_eoi_bug(void)
> +{
> + if (cpu_count() < 2)
> + return;
> +
> + set_idt_entry(0x84, pit_isr, 0);
> + __set_ioapic_redir(0x2, 0x84, EDGE_TRIGGERED, 0);
> +
> + outb(0x34, 0x43);
> +
> + for (unsigned loops = 100000000; loops && pit_working < 1; loops--)
> + asm volatile ("nop");
> +
> + report("dest_id reconfiguration before EOI", pit_working >= 1);
> +}
>
> int main(void)
> {
> @@ -325,5 +366,7 @@ int main(void)
> test_ioapic_level_mask();
> test_ioapic_level_retrigger_mask();
>
> + test_ioapic_eoi_bug();
> +
> return report_summary();
> }
>
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html