[SeaBIOS] Re: [PATCH 1/1] stacks: fix missing NMI_DISABLE_BIT on call32_post()

[Kevin O'Connor]

On Thu, May 27, 2021 at 09:25:01AM -0300, Heitor Alves de Siqueira wrote:
> We should disable NMIs when accessing CMOS ports during state restore,
> like it's done during state backup in call32_prep().
> Signed-off-by: Heitor Alves de Siqueira
>
> src/stacks.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/stacks.c b/src/stacks.c
> index 2fe1bfbd64fd..e315066d52e8 100644
> --- a/src/stacks.c
> +++ b/src/stacks.c
> @@ -107,7 +107,7 @@ call32_post(void)
>      // Restore cmos index register
>      u8 cmosindex = GET_LOW(Call16Data.cmosindex);
>      if (!(cmosindex & NMI_DISABLE_BIT)) {
>    outb(cmosindex, PORT_CMOS_INDEX);
>    outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
>    inb(PORT_CMOS_DATA);
> }

The purpose of this code is to restore the NMI_DISABLE_BIT to what it
was prior to call32_prep().  If something calls the bios without the
NMI_DISABLE_BIT set, it's this code that makes sure SeaBIOS returns to
that calling code with NMI_DISABLE_BIT also not set.

If you've run into some bug, I think it would help if you could
further describe that bug.

Cheers,
-Kevin