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

[Peter Maydell]

Ping?

-- PMM

On 17 January 2012 13:23, Peter Maydell <address@hidden> wrote:
> 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 <address@hidden>
> ---
> 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;
> --
> 1.7.1
>
>