From nobody Tue Dec 16 12:42:16 2025 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 51099146595 for ; Thu, 18 Jul 2024 22:35:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721342128; cv=none; b=V/eQE7V5zDirDpjQhW2mm5qPPyyCbNT/k/upgO2XGMm5T/M9PFNWeygqZeGVTFN+hazgRopH/QI5D05POztBNJ3UUSVUZ6HYyUv9UGYeBP/lc/HiNtVIvDrk7btDIgPAr9jOis4uRmvFk977GpNMvppGDRVfxNVXk6MbF55mbTU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721342128; c=relaxed/simple; bh=YDpDr4yxWaBJNXkK2yYee40+CDxF3GQ0b52/63eIRv0=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=pxOZiBiZgxHZ2TNmJd4YG+uMUbuFb+PeSnSXGjIpFVQTspfpYbz1j9WhcSyhhriDyKNwfq1DcTdfsqsx4paS3RW3EVewOzg7DCtZC0kK4XB1YGKh4G+B0TP0KzQ24el8Scx616UWKZzlu0JHR0uRjOaP2hFfJBDmGnTiOmAnN+E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--coltonlewis.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=l7cwWVWX; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--coltonlewis.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="l7cwWVWX" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-665a6dd38c8so37114347b3.1 for ; Thu, 18 Jul 2024 15:35:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1721342124; x=1721946924; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=t17NNug3pGXskbylK7023fOephyseDv5XvuuntGRCyI=; b=l7cwWVWXYbvOX9Qf3qSUn/wGUoHJOn+UUKIf8b7HO3UNvpRUY4EvbFUvfq+0hqtBf2 lT1DYPFB4beq0qBDO/16c1XjrUe9S6AhtcVpent3ZqFVu2agbP2iNQr2ugS0nle4n7e3 dZ5FiHCR0FgAcVNXfN3/ktgEckxHkiNN6uWj0I6mKVMy+jGxlN9Lm0fjCF3kmuDSNNkf 5FD+2k5YkLAzyIW+wvwn7ekjOBT+EwED/MlbIEQF4qx3jsD4ROf9NzO4Tl8u49Qn6Pox F62WERJsAmeu/LDNjSsdjzL32yNSYmz/QOSiTdr7nfs+CUicWQ1Opu21NHYWz/Aa3wPO oQWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721342124; x=1721946924; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=t17NNug3pGXskbylK7023fOephyseDv5XvuuntGRCyI=; b=Knbh7CBt14ZJ6c+rrG3LjjYapOgOLwrpvgaOzvftghA4iD7mEeWH1iepD4nFf9F1LA f/yYfh0Krhldeatg3zXVjn+T2E6tXLMLavI3+myaS5K1ERNq2nI8Q0IVGx/zUagySvZT GsMbrd9rTOjKK0CcqKcR05/fmx5+dPZ2Ov00fbD5Ta6hdFVTtqXLIzLJgFNeSMcMBfOk DGMV14CuafBV716OvKx+2ZIKXXwc6psYIP5XbpFTaVXXAQr/ff42lrg/zeK5+9aJsjcE mti4zKCF3WHF2ahIPe6Ho8WzM0vvUnR19yvPDyqVh6c7TRBpw+CssxCK6HXWSJovQ0CR KyWw== X-Forwarded-Encrypted: i=1; AJvYcCUthgL1nA7PEqtdtCKa39VSgdanTX7T3pWpbWUnIcGbMhHBuGrJCnyoB3+TBqJIw4IeLE7zrwYFzXchbIWXLPtz+QNi6nkuwf7s9UC0 X-Gm-Message-State: AOJu0YxEXzgFtHMfvvJA4DcaYheidw1pETty+K2eFe3yuSp/PpGY6Gdd NOllJgsrAL2Q452NUoBdhCm2qCqHHYzdcQA9PAH+E2NFGqrnoNpce+RjFjrU35mH5+pZhdxCZpL nx4fZb+lNhPMNjMQ/1WQlkA== X-Google-Smtp-Source: AGHT+IFAzxmz+xd5k+TsYOLSlTiwpUEcd3PMTkPrko0oISXqajR79Y7rD10ay46njNzlCvfw2OfNGwggk1RAW9y4Sw== X-Received: from coltonlewis-kvm.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:14ce]) (user=coltonlewis job=sendgmr) by 2002:a05:690c:f94:b0:627:a961:caee with SMTP id 00721157ae682-66603127fa6mr1628197b3.4.1721342124251; Thu, 18 Jul 2024 15:35:24 -0700 (PDT) Date: Thu, 18 Jul 2024 22:35:19 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.1089.g2a221341d9-goog Message-ID: <20240718223519.1673835-1-coltonlewis@google.com> Subject: [PATCH] KVM: arm64: Move data barrier to end of split walk From: Colton Lewis To: kvm@vger.kernel.org Cc: Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Colton Lewis Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Moving the data barrier from stage2_split_walker to after the walk is finished in kvm_pgtable_stage2_split results in a roughly 70% reduction in Clear Dirty Log Time in dirty_log_perf_test (modified to use eager page splitting) when using huge pages. This gain holds steady through a range of vcpus used (tested 1-64) and memory used (tested 1-64GB). This is safe to do because nothing else is using the page tables while they are still being mapped and this is how other page table walkers already function. None of them have a data barrier in the walker itself. Signed-off-by: Colton Lewis --- arch/arm64/kvm/hyp/pgtable.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 9e2bbee77491..9788af2ca8c0 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1547,7 +1547,6 @@ static int stage2_split_walker(const struct kvm_pgtab= le_visit_ctx *ctx, */ new =3D kvm_init_table_pte(childp, mm_ops); stage2_make_pte(ctx, new); - dsb(ishst); return 0; } =20 @@ -1559,8 +1558,11 @@ int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt= , u64 addr, u64 size, .flags =3D KVM_PGTABLE_WALK_LEAF, .arg =3D mc, }; + int ret; =20 - return kvm_pgtable_walk(pgt, addr, size, &walker); + ret =3D kvm_pgtable_walk(pgt, addr, size, &walker); + dsb(ishst); + return ret; } =20 int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *= mmu, --=20 2.45.2.1089.g2a221341d9-goog