From nobody Wed Oct 8 23:09:10 2025 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (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 310F327C16A for ; Tue, 24 Jun 2025 09:23:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750756992; cv=none; b=tQ+heRWrF7OLTYHrOUxVslMVVucLmxYYkPhPP3wCIE0ps15NfS5v+MTXwlpOGgxsAKGmL4ChtkZEui0nz6KJTVeiMAk6StNxIh6ZetYDbe36gHX9ZHaD+CPUGRWLRlql97f7Kyc9/sLtwse7BWquoF62wemRO8eP/Cf4XR8xSmg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750756992; c=relaxed/simple; bh=583wsMDBMJrMhyGcOptLAkwUC1sLZ7/fwnjcJ8OxnvE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=AYIngnjCnVI20zc6R81ZWIbrPEncAUW/fODWd/si+Zyc1FBQrOqhluksHWq5+ynfo9zH1YAsrb8kTifFpZ14Dyn7Mugid3Xm3V5Sp42dJ3QQm4dZFRWsDne7hxb2p0kOGVdBgS0KcPgf63MgttXlewmSbgz5cPmUOBZapl473C4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--keirf.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=gThEaZUq; arc=none smtp.client-ip=209.85.221.73 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--keirf.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gThEaZUq" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-3a4f6ba526eso3200909f8f.1 for ; Tue, 24 Jun 2025 02:23:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1750756989; x=1751361789; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=UC6vq5jBb1v1bd72k3pkcapbf6E4MjOjFHfh0Y/a140=; b=gThEaZUqaulHp8CvIs77Pkb5zR6fwiXv9ppwfm6bKgZh/zUVeL/JETqV9pBh3qt7Ei P+PxpqoWipRNQUezVszI/pd9NljmXvJk6AtG1CMXVkKZQQqfOYtjPMMbmjw8dCC+VS1q sbV4AB/DkW4uI6umuLD3cTZX/PtNMapWfSbUnA1rD83sg7oK3gpJPPdQIxUdUMLyOwGx v5roOXZMGgpLY3ES6TySj8sJy0xswP9UiFTZlMS880O4jF8dKjGnlORHbboAl6xRCaQC 8Jb38Kb/qR8dC0o6Pm98yBt5jZKT+lhpsujXnJuU/CVStWAJsMC5/FGJ8gyeRyvSWqtL o9Fg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750756989; x=1751361789; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UC6vq5jBb1v1bd72k3pkcapbf6E4MjOjFHfh0Y/a140=; b=wKZHnb2oP23mP4AJ0vFaht+VyEtzJx0nSGwrL50qUt9umaCPf13uzfoLNt3QC425XM tcBqAf0pWymqWxECwCTfQYT/5lON3FR7pNQ4cicp9c4QYKPcUyLk+Sr5CxYpEUxX8SSl DbG0d3uuZRK+0oF2Y2W73PCNJ+yKZwAMAKdY5JilmdxtP4v0ugq7erLGTH6HKYV28ODR IKkJEt+8YLe/wxXEucU6tQR4E582dz5ZnJj7tr1HOA/gTZcLV2yrTfZGsqN/5a3Rl0Hc 8XD5rf7314ihqzteNhbR8hNEgLqyrd3sF6mng1SxJr4beobW820yX3g/yCvW0i0sm6ha JeWw== X-Forwarded-Encrypted: i=1; AJvYcCXSJpeBPu25Jua2AiW7LAXgNxDJb2Xm0csAzL89ZRg7kJHIhOl3N2MYvb8BZxBqjkJuvQAVwXFEVwtP7ek=@vger.kernel.org X-Gm-Message-State: AOJu0YxlRkXUAQsFVY9HokvHHLoitnEQGyPv7caDqTUp+mwhWLAE1mSa i/NYMUz8S/VBzSE4dKuVYwKyYDsM9o9VaHCV6m2NglVcnbGTh6RT32nRUtQUatJ0ojDA7Y9eOjM yrw== X-Google-Smtp-Source: AGHT+IEr7r98giCBtL0yinhHNgdvxQNlG3HKjSDL95dDG4D8sHcl523PslIHgko1ki0lJc9tb1d51y0i9A== X-Received: from wmbdt3.prod.google.com ([2002:a05:600c:6303:b0:451:deba:e06f]) (user=keirf job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2582:b0:3a4:dc42:a0ac with SMTP id ffacd0b85a97d-3a6d1324294mr13113188f8f.49.1750756989691; Tue, 24 Jun 2025 02:23:09 -0700 (PDT) Date: Tue, 24 Jun 2025 09:22:54 +0000 In-Reply-To: <20250624092256.1105524-1-keirf@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250624092256.1105524-1-keirf@google.com> X-Mailer: git-send-email 2.50.0.rc2.761.g2dc52ea45b-goog Message-ID: <20250624092256.1105524-3-keirf@google.com> Subject: [PATCH 2/3] KVM: arm64: vgic: Explicitly implement vgic_dist::ready ordering From: Keir Fraser To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Eric Auger , Oliver Upton , Marc Zyngier , Will Deacon , Paolo Bonzini , Keir Fraser Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In preparation to remove synchronize_srcu() from MMIO registration, remove the distributor's dependency on this implicit barrier by direct acquire-release synchronization on the flag write and its lock-free check. Signed-off-by: Keir Fraser --- arch/arm64/kvm/vgic/vgic-init.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-ini= t.c index 502b65049703..bc83672e461b 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -567,7 +567,7 @@ int kvm_vgic_map_resources(struct kvm *kvm) gpa_t dist_base; int ret =3D 0; =20 - if (likely(dist->ready)) + if (likely(smp_load_acquire(&dist->ready))) return 0; =20 mutex_lock(&kvm->slots_lock); @@ -598,14 +598,7 @@ int kvm_vgic_map_resources(struct kvm *kvm) goto out_slots; } =20 - /* - * kvm_io_bus_register_dev() guarantees all readers see the new MMIO - * registration before returning through synchronize_srcu(), which also - * implies a full memory barrier. As such, marking the distributor as - * 'ready' here is guaranteed to be ordered after all vCPUs having seen - * a completely configured distributor. - */ - dist->ready =3D true; + smp_store_release(&dist->ready, true); goto out_slots; out: mutex_unlock(&kvm->arch.config_lock); --=20 2.50.0.rc2.761.g2dc52ea45b-goog