On Mon, 23 Jul 2012 20:41:29 +0200, Antonios Motakis <a.motakis at virtualopensystems.com> wrote: > This patch applies to the v9 patch series of KVM, > i.e. commit d5321dceeaccf756755e76b38d8b5905bd99d250 > > In this patch, we use the Hyp Coprocessor Trap Register > (HPCTR) to trap VFP/NEON instructions, and switch the FPU > state at that point. After a guest exit, the VFP state is > returned to the host. > > Initial lazy switching implementation provided by Rusty Russell. > > When disabling access to floating point instructions, we also mask > FPEXC_EN in order to avoid the guest receiving Undefined instruction > exceptions before we have a chance to switch back the floating point > state. Ah, I'd totally missed this, good catch. > One assumption in the patch is that FPEXC_EN will be off for > the host when we are about to enter the guest. Removing this assumption > is trivial, but it looks like it is always the case (comments?). If qemu uses floating point, it will be set, so we should fix this. Thanks, Rusty.
