[SeaBIOS] Re: [PATCH 3/3] qemu: check rtc presence before reading cpu count from cmos

[Philippe Mathieu-Daudé]

On 5/8/20 1:37 PM, Gerd Hoffmann wrote:
> Read month register which should never have a value larger than 12.
> In case the read returns 0xff assume the rtc isn't there.
> Don't try to read the cpu count from cmos without rtc.
>
> Signed-off-by: Gerd Hoffmann

Reviewed-by: Philippe Mathieu-Daudé
> src/fw/paravirt.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 3465f97ec0b0..e76fa65d87a0 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -447,6 +447,11 @@ qemu_get_romfile_key(struct romfile_s *file)
>       return qfile->select;
>   }
>
> +static int rtc_present(void)
> +{
> return rtc_read(CMOS_RTC_MONTH) != 0xff;
>
> +}
> u16
> qemu_get_present_cpus_count(void)
> {
>
> @@ -454,9 +459,11 @@ qemu_get_present_cpus_count(void)
>       if (qemu_cfg_enabled()) {
>           qemu_cfg_read_entry(&smp_count, QEMU_CFG_NB_CPUS, sizeof(smp_count));
>       }
> u16 cmos_cpu_count = rtc_read(CMOS_BIOS_SMP_COUNT) + 1;
> if (smp_count < cmos_cpu_count) {
>    smp_count = cmos_cpu_count;
> if (rtc_present()) {
>    u16 cmos_cpu_count = rtc_read(CMOS_BIOS_SMP_COUNT) + 1;
>    if (smp_count < cmos_cpu_count) {
>        smp_count = cmos_cpu_count;
>    }
> }
> return smp_count;
> }