On 6/4/20 5:30 PM, Peter Maydell wrote: > On Thu, 4 Jun 2020 at 16:16, Philippe Mathieu-Daudé <phi...@redhat.com> wrote: >> On 5/25/20 10:59 PM, Peter Maydell wrote: >>> What problem is this check solving? Is there some implementation >>> imposed limitation or a limit within the flash header format >>> that means larger sizes don't work? If so, what's the restriction? >> >> I am not confident maintaining virtual device with no specifications. > > This isn't a virtual device, is it? The CFI spec exists and defines > what these flash devices behave like. > >> If someone come with a datasheet for a pflash > 256MB then we can add >> another commit to relax this restriction. >> If someone is forced to use a >256MB and such hardware does not exist, >> I'd rather have a document in docs/specs/pflash_cfi01.rst describing the >> CFI fields. >> >> IOW this is not a hardware limitation, but a maintenance protection. >> >> I am worried with the recent EDK2 activity with the SBSA-ref, and I >> don't want to give false hope to developers that they can create any >> kind of pflash with the current device model. >> >> If I reword this better in the commit description, is my argument >> acceptable? > > Not really; I think we should know what we're limiting against. > Currently you're checking total_len, but this is just sector_len * nb_blocs, > so if there's a problem with silly large values then it's probably > actually a problem with one of those being over-sized which would > still show up even if the total_len was less than 256MB. > (I suspect the underlying limit here is what the cfi_table entries > 0x2D..0x30 impose on blocks_per_device and sector_len_per_device.)
What I'm working on is a whitelist of the few models our machines really use, but it is taking time. Meanwhile I wanted to at least limit the total size. I'll try to finish my whitelist effort before someone try to use a >256MB flash. > > thanks > -- PMM >
