From: "Yury Norov (NVIDIA)" <yury.norov@gmail.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Mark Brown <broonie@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Cc: "Yury Norov (NVIDIA)" <yury.norov@gmail.com>
Subject: [PATCH] arm64/fpsimd: simplify sme_setup()
Date: Fri, 12 Sep 2025 20:09:05 -0400 [thread overview]
Message-ID: <20250913000906.67086-1-yury.norov@gmail.com> (raw)
The function checks info->vq_map for emptiness right before calling
find_last_bit().
We can use the find_last_bit() output and save on bitmap_empty() call,
which is O(N).
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
arch/arm64/kernel/fpsimd.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index c37f02d7194e..e3f8f51748bc 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1265,6 +1265,8 @@ void __init sme_setup(void)
if (!system_supports_sme())
return;
+ min_bit = find_last_bit(info->vq_map, SVE_VQ_MAX);
+
/*
* SME doesn't require any particular vector length be
* supported but it does require at least one. We should have
@@ -1272,9 +1274,8 @@ void __init sme_setup(void)
* let's double check here. The bitmap is SVE_VQ_MAP sized for
* sharing with SVE.
*/
- WARN_ON(bitmap_empty(info->vq_map, SVE_VQ_MAX));
+ WARN_ON(min_bit >= SVE_VQ_MAX);
- min_bit = find_last_bit(info->vq_map, SVE_VQ_MAX);
info->min_vl = sve_vl_from_vq(__bit_to_vq(min_bit));
max_bit = find_first_bit(info->vq_map, SVE_VQ_MAX);
--
2.43.0
next reply other threads:[~2025-09-13 0:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-13 0:09 Yury Norov (NVIDIA) [this message]
2025-09-16 21:13 ` Will Deacon
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