Re: [PATCH v2] x86: Some cleanup of delay() and io_delay()

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/05/19 13:13, nadav.amit@gmail.com wrote:
> From: Nadav Amit <nadav.amit@gmail.com>
> 
> There is no guarantee that a self-IPI would be delivered immediately.
> In eventinj, io_delay() is called after self-IPI is generated but does
> nothing.
> 
> In general, there is mess in regard to delay() and io_delay(). There are
> two definitions of delay() and they do not really look on the timestamp
> counter and instead count invocations of "pause" (or even "nop"), which
> might be different on different CPUs/setups, for example due to
> different pause-loop-exiting configurations.
> 
> To address these issues change io_delay() to really do a delay, based on
> timestamp counter, and move common functions into delay.[hc].
> 
> Cc: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> Signed-off-by: Nadav Amit <nadav.amit@gmail.com>

Queued; there is another io_delay instance in taskswitch2.c, so I
removed it too.

Paolo

> ---
>  lib/x86/delay.c | 9 ++++++---
>  lib/x86/delay.h | 7 +++++++
>  x86/eventinj.c  | 5 +----
>  x86/ioapic.c    | 8 +-------
>  4 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/lib/x86/delay.c b/lib/x86/delay.c
> index 595ad24..e7d2717 100644
> --- a/lib/x86/delay.c
> +++ b/lib/x86/delay.c
> @@ -1,8 +1,11 @@
>  #include "delay.h"
> +#include "processor.h"
>  
>  void delay(u64 count)
>  {
> -	while (count--)
> -		asm volatile("pause");
> -}
> +	u64 start = rdtsc();
>  
> +	do {
> +		pause();
> +	} while (rdtsc() - start < count);
> +}
> diff --git a/lib/x86/delay.h b/lib/x86/delay.h
> index a9bf894..a51eb34 100644
> --- a/lib/x86/delay.h
> +++ b/lib/x86/delay.h
> @@ -3,6 +3,13 @@
>  
>  #include "libcflat.h"
>  
> +#define IPI_DELAY 1000000
> +
>  void delay(u64 count);
>  
> +static inline void io_delay(void)
> +{
> +	delay(IPI_DELAY);
> +}
> +
>  #endif
> diff --git a/x86/eventinj.c b/x86/eventinj.c
> index d2dfc40..901b9db 100644
> --- a/x86/eventinj.c
> +++ b/x86/eventinj.c
> @@ -7,6 +7,7 @@
>  #include "apic-defs.h"
>  #include "vmalloc.h"
>  #include "alloc_page.h"
> +#include "delay.h"
>  
>  #ifdef __x86_64__
>  #  define R "r"
> @@ -16,10 +17,6 @@
>  
>  void do_pf_tss(void);
>  
> -static inline void io_delay(void)
> -{
> -}
> -
>  static void apic_self_ipi(u8 v)
>  {
>  	apic_icr_write(APIC_DEST_SELF | APIC_DEST_PHYSICAL | APIC_DM_FIXED |
> diff --git a/x86/ioapic.c b/x86/ioapic.c
> index 2ac4ac6..c32dabd 100644
> --- a/x86/ioapic.c
> +++ b/x86/ioapic.c
> @@ -4,6 +4,7 @@
>  #include "smp.h"
>  #include "desc.h"
>  #include "isr.h"
> +#include "delay.h"
>  
>  static void toggle_irq_line(unsigned line)
>  {
> @@ -165,13 +166,6 @@ static void test_ioapic_level_tmr(bool expected_tmr_before)
>  	       expected_tmr_before ? "true" : "false");
>  }
>  
> -#define IPI_DELAY 1000000
> -
> -static void delay(int count)
> -{
> -	while(count--) asm("");
> -}
> -
>  static void toggle_irq_line_0x0e(void *data)
>  {
>  	irq_disable();
>