On Wed, 23 Nov 2022 11:25:08 +0100 Gerd Hoffmann <kra...@redhat.com> wrote:
> On Tue, Nov 22, 2022 at 01:43:16PM -0500, Kevin O'Connor wrote: > > On Mon, Nov 21, 2022 at 11:32:13AM +0100, Gerd Hoffmann wrote: > > > Current seabios code will only enable and use the 64bit pci io window in > > > case it runs out of space in the 32bit pci mmio window below 4G. > > > > > > This patch will also enable the 64bit pci io window when > > > (a) RAM above 4G is present, and > > > (b) the physical address space size is known, and > > > (c) seabios is running on a 64bit capable processor. > > > > > > This operates with the assumption that guests which are ok with memory > > > above 4G most likely can handle mmio above 4G too. > > > > Thanks. In general, the series looks good to me. Can you elaborate > > on the background to this change though? It sounds like there is a > > (small) risk of a regression, so I think it would be good to have a > > high level understanding of what is driving this memory reorg. > > Well, the idea is to adapt to the world moving forward. Running a > 64-bit capable OS is standard these days, and the resources needed > by devices (especially GPUs) are becoming larger and larger. > > Yes, there is the risk that (old) guests are unhappy with their > PCI bars suddenly being mapped above 4G. Can happen only in case > seabios handles pci initialization (i.e. when running on qemu, > otherwise coreboot initializes the pci bars). I hope the memory > check handles the 'old guest' case: when the guest can't handle > addresses above 4G it is unlikely that qemu is configured to have > memory mapped above 4G ... does it break 32-bit PAE enabled guests (which can have more then 4Gb RAM configured)? > > take care, > Gerd > > _______________________________________________ > SeaBIOS mailing list -- seab...@seabios.org > To unsubscribe send an email to seabios-le...@seabios.org >