arm64: KVM: VHE: Patch out use of HVC

With VHE, the host never issues an HVC instruction to get into the
KVM code, as we can simply branch there.

Use runtime code patching to simplify things a bit.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 0ccdcbb..0689a74 100644 (file)
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -17,7 +17,9 @@
 
 #include <linux/linkage.h>
 
+#include <asm/alternative.h>
 #include <asm/assembler.h>
+#include <asm/cpufeature.h>
 
 /*
  * u64 kvm_call_hyp(void *hypfn, ...);
@@ -38,6 +40,11 @@
  * arch/arm64/kernel/hyp_stub.S.
  */
 ENTRY(kvm_call_hyp)
+alternative_if_not ARM64_HAS_VIRT_HOST_EXTN    
        hvc     #0
        ret
+alternative_else
+       b       __vhe_hyp_call
+       nop
+alternative_endif
 ENDPROC(kvm_call_hyp)

diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 93e8d98..1bdeee7 100644 (file)
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -38,6 +38,34 @@
        ldp     x0, x1, [sp], #16
 .endm
 
+.macro do_el2_call
+       /*
+        * Shuffle the parameters before calling the function
+        * pointed to in x0. Assumes parameters in x[1,2,3].
+        */
+       sub     sp, sp, #16
+       str     lr, [sp]
+       mov     lr, x0
+       mov     x0, x1
+       mov     x1, x2
+       mov     x2, x3
+       blr     lr
+       ldr     lr, [sp]
+       add     sp, sp, #16
+.endm
+
+ENTRY(__vhe_hyp_call)
+       do_el2_call
+       /*
+        * We used to rely on having an exception return to get
+        * an implicit isb. In the E2H case, we don't have it anymore.
+        * rather than changing all the leaf functions, just do it here
+        * before returning to the rest of the kernel.
+        */
+       isb
+       ret
+ENDPROC(__vhe_hyp_call)
+       
 el1_sync:                              // Guest trapped into EL2
        save_x0_to_x3
 
@@ -58,19 +86,13 @@ el1_sync:                           // Guest trapped into EL2
        mrs     x0, vbar_el2
        b       2f
 
-1:     stp     lr, xzr, [sp, #-16]!
-
+1:
        /*
-        * Compute the function address in EL2, and shuffle the parameters.
+        * Perform the EL2 call
         */
        kern_hyp_va     x0
-       mov     lr, x0
-       mov     x0, x1
-       mov     x1, x2
-       mov     x2, x3
-       blr     lr
+       do_el2_call
 
-       ldp     lr, xzr, [sp], #16
 2:     eret
 
 el1_trap: