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Subject[PATCH 5.4 081/109] KVM: arm64: Stop clobbering x0 for HVC_SOFT_RESTART
Date
From: Andrew Scull <ascull@google.com>

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>

---
arch/arm64/kvm/hyp-init.S | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -136,11 +136,15 @@ 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
@@ -151,7 +155,6 @@ reset:
/* Install stub vectors */
adr_l x5, __hyp_stub_vectors
msr vbar_el2, x5
- mov x0, xzr
eret

1: /* Bad stub call */

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