On Sun, 22 Aug 2021 at 15:45, Marc Zyngier <maz@xxxxxxxxxx> wrote: > > The documentation for the 'highmem' option indicates that it controls > the placement of both devices and RAM. The actual behaviour of QEMU > seems to be that RAM is allowed to go beyond the 4GiB limit, and > that only devices are constraint by this option. > > Align the documentation with the actual behaviour. I think it would be better to align the behaviour with the documentation. The intent of 'highmem' is to allow a configuration for use with guests that can't address more than 32 bits (originally, 32-bit guests without LPAE support compiled in). It seems like a bug that we allow the user to specify more RAM than will fit into that 32-bit range. We should instead make QEMU exit with an error if the user tries to specify both highmem=off and a memory size that's too big to fit. thanks -- PMM
