From: Will Deacon <will@kernel.org>
To: kvmarm@lists.cs.columbia.edu
Cc: Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Alexandru Elisei <alexandru.elisei@arm.com>,
kernel-team@android.com, linux-arm-kernel@lists.infradead.org,
David Brazdil <dbrazdil@google.com>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH 4/6] KVM: arm64: Extend comment in has_vhe()
Date: Thu, 9 Jun 2022 13:12:21 +0100 [thread overview]
Message-ID: <20220609121223.2551-5-will@kernel.org> (raw)
In-Reply-To: <20220609121223.2551-1-will@kernel.org>
has_vhe() expands to a compile-time constant when evaluated from the VHE
or nVHE code, alternatively checking a static key when called from
elsewhere in the kernel. On face value, this looks like a case of
premature optimization, but in fact this allows symbol references on
VHE-specific code paths to be dropped from the nVHE object.
Expand the comment in has_vhe() to make this clearer, hopefully
discouraging anybody from simplifying the code.
Cc: David Brazdil <dbrazdil@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/virt.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 3c8af033a997..0e80db4327b6 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -113,6 +113,9 @@ static __always_inline bool has_vhe(void)
/*
* Code only run in VHE/NVHE hyp context can assume VHE is present or
* absent. Otherwise fall back to caps.
+ * This allows the compiler to discard VHE-specific code from the
+ * nVHE object, reducing the number of external symbol references
+ * needed to link.
*/
if (is_vhe_hyp_code())
return true;
--
2.36.1.255.ge46751e96f-goog
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next prev parent reply other threads:[~2022-06-09 12:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-09 12:12 [PATCH 0/6] KVM/arm64: Minor/trivial fixes from pKVM mega-patch Will Deacon
2022-06-09 12:12 ` [PATCH 1/6] KVM: arm64: Return error from kvm_arch_init_vm() on allocation failure Will Deacon
2022-06-09 12:12 ` [PATCH 2/6] KVM: arm64: Handle all ID registers trapped for a protected VM Will Deacon
2022-06-14 5:57 ` Reiji Watanabe
2022-06-09 12:12 ` [PATCH 3/6] KVM: arm64: Ignore 'kvm-arm.mode=protected' when using VHE Will Deacon
2022-06-09 12:12 ` Will Deacon [this message]
2022-06-09 12:12 ` [PATCH 5/6] KVM: arm64: Remove redundant hyp_assert_lock_held() assertions Will Deacon
2022-06-09 12:12 ` [PATCH 6/6] KVM: arm64: Drop stale comment Will Deacon
2022-06-09 12:19 ` [PATCH 0/6] KVM/arm64: Minor/trivial fixes from pKVM mega-patch Marc Zyngier
2022-06-09 12:26 ` Marc Zyngier
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