Re: [PATCH] hw/i386/cxl: ensure maxram is greater than ram size for calculating cxl range

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Wed, 11 Oct 2023 16:23:35 +0530
Ani Sinha <anisinha@redhat.com> wrote:

> pc_get_device_memory_range() finds the device memory size by calculating the
> difference between maxram and ram sizes. This calculation makes sense only when
> maxram is greater than the ram size. Make sure we check for that before calling
> pc_get_device_memory_range().
> 
> Signed-off-by: Ani Sinha <anisinha@redhat.com>

Whilst this is similar to other cases, I can't remember or quickly work
out if the 'else' path here is appropriate.  Can we add something to the
patch description to talk about that?

For reference it's:

cxl_base = pc_above_4g_end(pcms);

> ---
>  hw/i386/pc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index f72e2c3b35..948c58171c 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -820,10 +820,12 @@ static void pc_get_device_memory_range(PCMachineState *pcms,
>  static uint64_t pc_get_cxl_range_start(PCMachineState *pcms)
>  {
>      PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> +    MachineState *ms = MACHINE(pcms);
>      hwaddr cxl_base;
>      ram_addr_t size;
>  
> -    if (pcmc->has_reserved_memory) {
> +    if (pcmc->has_reserved_memory &&
> +        (ms->ram_size < ms->maxram_size)) {
>          pc_get_device_memory_range(pcms, &cxl_base, &size);
>          cxl_base += size;
>      } else {