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From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	stable@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	Andrew Murray <amurray@thegoodpenguin.co.uk>
Subject: [PATCH 2/2] KVM: arm64: Stop clobbering x0 for HVC_SOFT_RESTART
Date: Mon,  6 Jul 2020 12:05:21 +0100
Message-ID: <20200706110521.1615794-3-maz@kernel.org> (raw)
In-Reply-To: <20200706110521.1615794-1-maz@kernel.org>

From: Andrew Scull <ascull@google.com>

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

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 6e6ed5581eed..e76c0e89d48e 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -136,11 +136,15 @@ SYM_CODE_START(__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
 	mov_q	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 */
-- 
2.27.0

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  parent reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-06 11:05 [PATCH 0/2] KVM/arm64 fixes for 5.8, take #3 Marc Zyngier
2020-07-06 11:05 ` [PATCH 1/2] KVM: arm64: PMU: Fix per-CPU access in preemptible context Marc Zyngier
2020-07-06 11:05 ` Marc Zyngier [this message]
2020-07-06 17:05 ` [PATCH 0/2] KVM/arm64 fixes for 5.8, take #3 Paolo Bonzini

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