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From: James Morse <james.morse@arm.com>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: Marc Zyngier <marc.zyngier@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>
Subject: [PATCH v2 3/6] KVM: arm64: Make indirect vectors preamble behaviour symmetric
Date: Mon, 10 Jun 2019 17:24:24 +0100
Message-ID: <20190610162427.115910-4-james.morse@arm.com> (raw)
In-Reply-To: <20190610162427.115910-1-james.morse@arm.com>

The KVM indirect vectors support is a little complicated. Different CPUs
may use different exception vectors for KVM that are generated at boot.
Adding new instructions involves checking all the possible combinations
do the right thing.

To make changes here easier to review lets state what we expect of the
preamble:
  1. The first vector run, must always run the preamble.
  2. Patching the head or tail of the vector shouldn't remove
     preamble instructions.

Today, this is easy as we only have one instruction in the preamble.
Change the unpatched tail of the indirect vector so that it always
runs this, regardless of patching.

Signed-off-by: James Morse <james.morse@arm.com>
---
New for v2.

 arch/arm64/kvm/hyp/hyp-entry.S | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index c7f9d5e271a9..5f0412f124a3 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -286,7 +286,7 @@ ENDPROC(__kvm_hyp_vector)
 /*
  * The default sequence is to directly branch to the KVM vectors,
  * using the computed offset. This applies for VHE as well as
- * !ARM64_HARDEN_EL2_VECTORS.
+ * !ARM64_HARDEN_EL2_VECTORS. The first vector must always run the preamble.
  *
  * For ARM64_HARDEN_EL2_VECTORS configurations, this gets replaced
  * with:
@@ -302,8 +302,8 @@ ENDPROC(__kvm_hyp_vector)
  * See kvm_patch_vector_branch for details.
  */
 alternative_cb	kvm_patch_vector_branch
-	b	__kvm_hyp_vector + (1b - 0b)
-	nop
+	stp	x0, x1, [sp, #-16]!
+	b	__kvm_hyp_vector + (1b - 0b + KVM_VECTOR_PREAMBLE)
 	nop
 	nop
 	nop
-- 
2.20.1

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Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-10 16:24 [PATCH v2 0/6] KVM: arm64: Account host/guest SError more precisely (Neoverse-N1 #1349291) James Morse
2019-06-10 16:24 ` [PATCH v2 1/6] arm64: assember: Switch ESB-instruction with a vanilla nop if !ARM64_HAS_RAS James Morse
2019-06-10 16:24 ` [PATCH v2 2/6] KVM: arm64: Abstract the size of the HYP vectors pre-amble James Morse
2019-06-10 16:24 ` James Morse [this message]
2019-06-10 16:24 ` [PATCH v2 4/6] KVM: arm64: Consume pending SError as early as possible James Morse
2019-06-10 16:24 ` [PATCH v2 5/6] KVM: arm64: Defer guest entry when an asynchronous exception is pending James Morse
2019-06-10 17:01   ` Marc Zyngier
2019-06-10 16:24 ` [PATCH v2 6/6] arm64: Update silicon-errata.txt for Neoverse-N1 #1349291 James Morse

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