On Tue, Mar 21, 2017 at 07:20:37PM +0000, Marc Zyngier wrote: > We now have a full hyp-stub implementation in the KVM init code, > but the main KVM code only supports HVC_GET_VECTORS, which is not > enough. > > Instead of reinventing the wheel, let's reuse the init implementation > by branching to the idmap page when called with a hyp-stub hypercall. > > Reviewed-by: James Morse <james.morse@xxxxxxx> > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > --- > arch/arm64/kvm/hyp/hyp-entry.S | 24 +++++++++++++++++++----- > 1 file changed, 19 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > index d8ef788646c6..4f34c5996f86 100644 > --- a/arch/arm64/kvm/hyp/hyp-entry.S > +++ b/arch/arm64/kvm/hyp/hyp-entry.S > @@ -87,10 +87,24 @@ alternative_endif > /* Here, we're pretty sure the host called HVC. */ > ldp x0, x1, [sp], #16 > > - cmp x0, #HVC_GET_VECTORS > - b.ne 1f > - mrs x0, vbar_el2 > - b 2f > + /* Check for a stub HVC call */ > + cmp x0, #HVC_STUB_HCALL_NR > + b.hs 1f > + > + /* > + * Compute the idmap address of __kvm_handle_stub_hvc and > + * jump there. Since we use kimage_voffset, do not use the > + * HYP VA for __kvm_handle_stub_hvc, but the kernel VA instead > + * (by loading it from the constant pool). > + * > + * Preserve x0-x4, which may contain stub parameters. > + */ > + ldr x5, =__kvm_handle_stub_hvc > + ldr_l x6, kimage_voffset Isn't it a bit dodgy to just overwrite x5 and x6 in something which is not a function? I know that in practice this always gets called through a function call and we can rely on the calling convention, but this can break if you issue a hypercall to KVM's HVC sub implementation using inline assembly, I think. Am I missing something here? > + > + /* x5 = __pa(x5) */ > + sub x5, x5, x6 > + br x5 > > 1: > /* > @@ -99,7 +113,7 @@ alternative_endif > kern_hyp_va x0 > do_el2_call > > -2: eret > + eret > > el1_trap: > /* > -- > 2.11.0 > Thanks, -Christoffer
