KVM: arm64: Extend comment in has_vhe()

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>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220609121223.2551-5-will@kernel.org

diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 3c8af03..0e80db4 100644 (file)
--- 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;