Re: [PATCH 1/2] acpi/crs: Prevent bad ranges for host bridges

[Igor Mammedov]

On Mon, 26 Oct 2020 12:39:23 -0700
Ben Widawsky <ben.widawsky@intel.com> wrote:

> Prevent _CRS resources being quietly chopped off and instead throw an
> assertion. _CRS is used by host bridges to declare regions of io and/or
> memory that they consume. On some (all?) platforms the host bridge
> doesn't have PCI header space and so they need some way to convey the
> information.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>

Acked-by: Igor Mammedov <imammedo@redhat.com>

> ---
> 
> 1. I'm not aware of this being a real issue on platforms today as I think
>    many platforms that use ACPI and actually have regions, constrain to
>    32b to be complaint with legacy.
> 2. Since host bridges aren't usually hot plugged, it can't be invoked by
>    a user, so assert() seems like the right way to handle this.
> ---
>  hw/i386/acpi-build.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index eee7b57c37..df13abecf4 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -869,6 +869,8 @@ static Aml *build_crs(PCIHostState *host, CrsRangeSet 
> *range_set)
>      crs_range_merge(temp_range_set.mem_ranges);
>      for (i = 0; i < temp_range_set.mem_ranges->len; i++) {
>          entry = g_ptr_array_index(temp_range_set.mem_ranges, i);
> +        assert(entry->limit <= UINT32_MAX &&
> +               (entry->limit - entry->base + 1) <= UINT32_MAX);
>          aml_append(crs,
>                     aml_dword_memory(AML_POS_DECODE, AML_MIN_FIXED,
>                                      AML_MAX_FIXED, AML_NON_CACHEABLE,