KVM: arm64: Avoid corrupting vCPU context register in guest exit

commit 31948332d5fa392ad933f4a6a10026850649ed76 upstream.

Commit 7db21530479f ("KVM: arm64: Restore hyp when panicking in guest
context") tracks the currently running vCPU, clearing the pointer to
NULL on exit from a guest.

Unfortunately, the use of 'set_loaded_vcpu' clobbers x1 to point at the
kvm_hyp_ctxt instead of the vCPU context, causing the subsequent RAS
code to go off into the weeds when it saves the DISR assuming that the
CPU context is embedded in a struct vCPU.

Leave x1 alone and use x3 as a temporary register instead when clearing
the vCPU on the guest exit path.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Andrew Scull <ascull@google.com>
Cc: <stable@vger.kernel.org>
Fixes: 7db21530479f ("KVM: arm64: Restore hyp when panicking in guest context")
Suggested-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210226181211.14542-1-will@kernel.org
Message-Id: <20210305185254.3730990-3-maz@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index b0afad7..0c66a1d 100644 (file)
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -146,7 +146,7 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
        // Now restore the hyp regs
        restore_callee_saved_regs x2
 
-       set_loaded_vcpu xzr, x1, x2
+       set_loaded_vcpu xzr, x2, x3
 
 alternative_if ARM64_HAS_RAS_EXTN
        // If we have the RAS extensions we can consume a pending error