Subject: [PATCH 2/4] KVM: arm64: Extend comment in has_vhe()

From: Will Deacon <[email-masked]>
Date: Thu, 3 Jun 2021 19:33:45 +0100

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 <[email-masked]>
Signed-off-by: Will Deacon <[email-masked]>
---
 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 7379f35ae2c6..3218ca17f819 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -111,6 +111,9 @@ 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;
-- 
2.32.0.rc0.204.g9fa02ecfa5-goog

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