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KVM: arm64: Stop handle_exit() from handling HVC twice when an SError occurs

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Prior to commit defe21f49b ("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 defe21f49b didn't preserve the behaviour of the 'return 1'
that skips the rest of handle_exit().

Since commit defe21f49b, 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: defe21f49b ("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
This commit is contained in:
James Morse 2022-01-27 12:20:51 +00:00 committed by Marc Zyngier
parent 1c71dbc8a1
commit 1229630af8
1 changed files with 8 additions and 0 deletions
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8
arch/arm64/kvm/handle_exit.c
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@ -228,6 +228,14 @@ int handle_exit(struct kvm_vcpu *vcpu, int exception_index)
{
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) {