linux-kernel - [PATCH v2 1/3] KVM: arm64: Constraint KVM's own __flush_dcache

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Date:   Mon, 22 Mar 2021 17:56:37 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     catalin.marinas@....com, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        android-kvm@...gle.com, seanjc@...gle.com, mate.toth-pal@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com, kvmarm@...ts.cs.columbia.edu,
        tabba@...gle.com, ardb@...nel.org, mark.rutland@....com,
        dbrazdil@...gle.com
Subject: [PATCH v2 1/3] KVM: arm64: Constraint KVM's own __flush_dcache_area to protectected mode

As we are about to specialise KVM's version of __flush_dcache_area
via a hack on the read_ctr macro, make sure that we won't ever
use KVM's copy of __flush_dcache_area(), as things would otherwise
break for late arriving CPUs.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kvm/hyp/nvhe/cache.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/cache.S b/arch/arm64/kvm/hyp/nvhe/cache.S
index 36cef6915428..1c177d3ec5c6 100644
--- a/arch/arm64/kvm/hyp/nvhe/cache.S
+++ b/arch/arm64/kvm/hyp/nvhe/cache.S
@@ -6,8 +6,12 @@
 #include <linux/linkage.h>
 #include <asm/assembler.h>
 #include <asm/alternative.h>
+#include <asm/asm-bug.h>
 
 SYM_FUNC_START_PI(__flush_dcache_area)
+alternative_if_not ARM64_KVM_PROTECTED_MODE
+	ASM_BUG()
+alternative_else_nop_endif
 	dcache_by_line_op civac, sy, x0, x1, x2, x3
 	ret
 SYM_FUNC_END_PI(__flush_dcache_area)
-- 
2.29.2