On 24/03/17 14:33, Christoffer Dall wrote:

On Tue, Mar 21, 2017 at 07:20:35PM +0000, Marc Zyngier wrote:

quoted

In order to restore HYP mode to its original condition, KVM currently
implements __kvm_hyp_reset(). As we're moving towards a hyp-stub
defined API, it becomes necessary to implement HVC_RESET_VECTORS.

This patch adds the HVC_RESET_VECTORS hypercall to the KVM init
code, which so far lacked any form of hypercall support.

Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <redacted>
---
 arch/arm64/kvm/hyp-init.S | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 6b29d3d9e1f2..6cf98ccd10f2 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S

@@ -22,6 +22,7 @@
 #include <asm/kvm_mmu.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/sysreg.h>
+#include <asm/virt.h>
 
 	.text
 	.pushsection	.hyp.idmap.text, "ax"

@@ -58,6 +59,9 @@ __invalid:
 	 * x2: HYP vectors
 	 */
 __do_hyp_init:
+	/* Check for a stub HVC call */
+	cmp	x0, #HVC_STUB_HCALL_NR
+	b.lo	__kvm_handle_stub_hvc
 
 	msr	ttbr0_el2, x0
 

@@ -119,6 +123,9 @@ __do_hyp_init:
 	eret
 ENDPROC(__kvm_hyp_init)
 
+ENTRY(__kvm_handle_stub_hvc)
+	cmp	x0, #HVC_RESET_VECTORS
+	b.ne	1f
 	/*
 	 * Reset kvm back to the hyp stub.
 	 */

@@ -133,9 +140,14 @@ ENTRY(__kvm_hyp_reset)
 	/* Install stub vectors */
 	adr_l	x0, __hyp_stub_vectors
 	msr	vbar_el2, x0
+	b	exit
 
+1:	mov	x0, #-1

nit: do we have the -1 return value documented somewhere and should we
define it as HVC_SUB_ERR_RETURN or something like that?

Indeed, this is something that is a bit dodgy. arm64 returns
ARM_EXCEPTION_HYP_GONE, which is really a KVM exception code (and isn't
-1 either). I'll try to tighten this up a bit.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...