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From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.cs.columbia.edu
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Will Deacon <will@kernel.org>,
	kernel-team@android.com,
	Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH] KVM: arm64: Prevent vcpu_has_ptrauth from generating OOL functions
Date: Wed, 22 Jul 2020 17:22:31 +0100
Message-ID: <20200722162231.3689767-1-maz@kernel.org> (raw)

So far, vcpu_has_ptrauth() is implemented in terms of system_supports_*_auth()
calls, which are declared "inline". In some specific conditions (clang
and SCS), the "inline" very much turns into an "out of line", which
leads to a fireworks when this predicate is evaluated on a non-VHE
system (right at the beginning of __hyp_handle_ptrauth).

Instead, make sure vcpu_has_ptrauth gets expanded inline by directly
using the cpus_have_final_cap() helpers, which are __always_inline,
generate much better code, and are the only thing that make sense when
running at EL2 on a nVHE system.

Fixes: 29eb5a3c57f7 ("KVM: arm64: Handle PtrAuth traps early")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 147064314abf..a8278f6873e6 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -391,9 +391,14 @@ struct kvm_vcpu_arch {
 #define vcpu_has_sve(vcpu) (system_supports_sve() && \
 			    ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE))
 
-#define vcpu_has_ptrauth(vcpu)	((system_supports_address_auth() || \
-				  system_supports_generic_auth()) && \
-				 ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH))
+#ifdef CONFIG_ARM64_PTR_AUTH
+#define vcpu_has_ptrauth(vcpu)						\
+	((cpus_have_final_cap(ARM64_HAS_ADDRESS_AUTH) ||		\
+	  cpus_have_final_cap(ARM64_HAS_GENERIC_AUTH)) &&		\
+	 (vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_PTRAUTH)
+#else
+#define vcpu_has_ptrauth(vcpu)		false
+#endif
 
 #define vcpu_gp_regs(v)		(&(v)->arch.ctxt.gp_regs)
 
-- 
2.28.0.rc0.142.g3c755180ce-goog


             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-22 16:22 Marc Zyngier [this message]
2020-07-23  2:51 ` Nathan Chancellor
2020-07-23  3:30   ` Zenghui Yu
2020-07-23  8:17   ` Marc Zyngier
2020-07-23 15:59     ` Nathan Chancellor

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