KVM: arm64: Stop clobbering x0 for HVC_SOFT_RESTART

commit b9e10d4a6c9f5cbe6369ce2c17ebc67d2e5a4be5 upstream.

HVC_SOFT_RESTART is given values for x0-2 that it should installed
before exiting to the new address so should not set x0 to stub HVC
success or failure code.

Fixes: af42f20480bf1 ("arm64: hyp-stub: Zero x0 on successful stub handling")
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200706095259.1338221-1-ascull@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index dea20651a5f167e70f1d38b9728d263a0c78eb58..cb28c12d0a64b91cff92c9268f06d1c2f5344204 100644 (file)
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -147,11 +147,15 @@ ENTRY(__kvm_handle_stub_hvc)
 
 1:     cmp     x0, #HVC_RESET_VECTORS
        b.ne    1f
-reset:
+
        /*
-        * Reset kvm back to the hyp stub. Do not clobber x0-x4 in
-        * case we coming via HVC_SOFT_RESTART.
+        * Set the HVC_RESET_VECTORS return code before entering the common
+        * path so that we do not clobber x0-x2 in case we are coming via
+        * HVC_SOFT_RESTART.
         */
+       mov     x0, xzr
+reset:
+       /* Reset kvm back to the hyp stub. */
        mrs     x5, sctlr_el2
        ldr     x6, =SCTLR_ELx_FLAGS
        bic     x5, x5, x6              // Clear SCTL_M and etc
@@ -162,7 +166,6 @@ reset:
        /* Install stub vectors */
        adr_l   x5, __hyp_stub_vectors
        msr     vbar_el2, x5
-       mov     x0, xzr
        eret
 
 1:     /* Bad stub call */