Hello, While adding support for para-virtualized block device in u-boot
I faced an issue with HYPERVISOR_console_io + CONSOLEIO_write. I tried to use the hypercall during MMU setup stage while enabling data cache on arm64 platform (e.g. data cache is not yet enabled) and saw in guest's console either old data or some sort of garbage. Printing constant strings, just like mini-os does on boot, works as expected. So, looking at the Xen code [1] it seems that we should copy guest's buffer with COPY_flush_dcache set in this case as (usually?) this hypercall is used in guest's code which doesn't have any other means to print yet, e.g. early printk case. If my understanding of the issue correct then I can probably prepare a patch. Thank you, Oleksandr [1] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/drivers/char/console.c;h=56e24821b2f8d2b9bfb99d2acb721b06277834ce;hb=refs/heads/master#l597
