On 21.05.2012, at 10:59, Benjamin Herrenschmidt wrote: > On Mon, 2012-05-21 at 10:38 +0200, Alexander Graf wrote: >> On 21.05.2012, at 09:24, Benjamin Herrenschmidt wrote: >> >>> This adds a kvm-specific hypervisor call to the pseries machine >>> which allows to do what amounts to memmove, memcpy and xor over >>> regions of physical memory such as the framebuffer. >>> >>> This is the simplest way to get usable framebuffer speed from >>> SLOF since the framebuffer isn't mapped in the VRMA and so would >>> otherwise require an hcall per 8 bytes access. >>> >>> The performance is still not great but usable, and can be improved >>> with a more complex implementation of the hcall itself if needed. >> >> Shouldn't we try and implement the same thing in QEMU as well to make >> things compatible? Also, what would the downside be of always going >> through QEMU for this hypercall? >> >> The reason I'm asking is that we might want to do memmove,memcpy,xor >> on MMIO memory, which then user space could easily do, but which >> incurs quite some headaches to do it from inside KVM. > > I don't understand your question ... this is implemented in qemu... > > The problem with SLOF is specific to -M pseries, because it runs in > "guest" real mode, it doesn't have access to device memory unless it > does it via hcalls. Yikes. Call me stupid. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
