From: James Morse <james.morse@arm.com>
Date: Thu, 27 Jan 2022 12:20:51 +0000
Subject: KVM: arm64: Stop handle_exit() from handling HVC twice when an SError
 occurs
Git-commit: 1229630af88620f6e3a621a1ebd1ca14d9340df7
Patch-mainline: v5.17-rc3
References: git-fixes

Prior to commit defe21f49bc9 ("KVM: arm64: Move PC rollback on SError to
HYP"), when an SError is synchronised due to another exception, KVM
handles the SError first. If the guest survives, the instruction that
triggered the original exception is re-exectued to handle the first
exception. HVC is treated as a special case as the instruction wouldn't
normally be re-exectued, as its not a trap.

Commit defe21f49bc9 didn't preserve the behaviour of the 'return 1'
that skips the rest of handle_exit().

Since commit defe21f49bc9, KVM will try to handle the SError and the
original exception at the same time. When the exception was an HVC,
fixup_guest_exit() has already rolled back ELR_EL2, meaning if the
guest has virtual SError masked, it will execute and handle the HVC
twice.

Restore the original behaviour.

Fixes: defe21f49bc9 ("KVM: arm64: Move PC rollback on SError to HYP")
Cc: stable@vger.kernel.org
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127122052.1584324-4-james.morse@arm.com

Acked-by: Ivan T. Ivanov <iivanov@suse.de>
---
 arch/arm64/kvm/handle_exit.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -240,6 +240,14 @@ int handle_exit(struct kvm_vcpu *vcpu, i
 {
 	struct kvm_run *run = vcpu->run;
 
+	if (ARM_SERROR_PENDING(exception_index)) {
+		/*
+		 * The SError is handled by handle_exit_early(). If the guest
+		 * survives it will re-execute the original instruction.
+		 */
+		return 1;
+	}
+
 	exception_index = ARM_EXCEPTION_CODE(exception_index);
 
 	switch (exception_index) {