Re: [Qemu-trivial] [Qemu-devel] [PATCH] exec.c: Clarify comment about tlb_flush() flush_global parameter

Re: [Qemu-trivial] [Qemu-devel] [PATCH] exec.c: Clarify comment about tlb_flush() flush_global parameter

[Andreas Färber]

Am 17.01.2012 14:23, schrieb Peter Maydell:
> Clarify the comment about tlb_flush()'s flush_global parameter,
> so it is clearer what it does and why it is OK that the implementation
> currently ignores it.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Andreas Färber <afaerber@suse.de>

CC'ing qemu-trivial.

Andreas

> ---
> Minor clarification following a conversation on IRC...
> 
>  exec.c |   14 ++++++++++++--
>  1 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 7f9f730..f667cf0 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1876,8 +1876,18 @@ static CPUTLBEntry s_cputlb_empty_entry = {
>      .addend     = -1,
>  };
>  
> -/* NOTE: if flush_global is true, also flush global entries (not
> -   implemented yet) */
> +/* NOTE:
> + * If flush_global is true (the usual case), flush all tlb entries.
> + * If flush_global is false, flush (at least) all tlb entries not
> + * marked global.
> + *
> + * Since QEMU doesn't currently implement a global/not-global flag
> + * for tlb entries, at the moment tlb_flush() will also flush all
> + * tlb entries in the flush_global == false case. This is OK because
> + * CPU architectures generally permit an implementation to drop
> + * entries from the TLB at any time, so flushing more entries than
> + * required is only an efficiency issue, not a correctness issue.
> + */
>  void tlb_flush(CPUState *env, int flush_global)
>  {
>      int i;

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