From nobody Sat Oct 4 09:39:46 2025 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (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 1CC5231A054 for ; Tue, 19 Aug 2025 09:09:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755594542; cv=none; b=Zd68lWnZ+Cf7cV/v5TDfX3mfq+aJs0ZDd2nouYLI0DUB9848547arnDglWmUtcOcy6YMxtoyJppRMfa55+ij2RxozPvZFFykXVXCghxqrBTCFE3QsVdIYYq4o+BAz2ve70AzzhZfo/tgREePkVjZnnsQKjsYEOz+qs6Qz64Iokw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755594542; c=relaxed/simple; bh=Lj8R+QAbvGD/j2/IfIqy36p+Mv51YViuIDGXC2HRQXM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=KBfGdJFicWVS4D/FjmtaP4Skf65RToB0Pz1sXb70W0zlr7zXEnuPPuj9MJFP3sSNZnAtZtHD080oiTEPV6kx31E3Gm2pptmp/+EAtSz1BDvCgnpnjGvaZKrg/4rm/55kcI/vuWfu8vgKWVaX7pBXDgfk47c7YzDJdRbzrv+UTQ8= 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=IbYXET9f; arc=none smtp.client-ip=209.85.128.74 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="IbYXET9f" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-45a1b05b15eso35990395e9.1 for ; Tue, 19 Aug 2025 02:09:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1755594539; x=1756199339; 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=b7GQRkJjLj0j3dNMqeMnq8zCLevsX26SkayOg/7wVlQ=; b=IbYXET9fBZ6ANe2D6j+vU9pkGZuz09OzoA2CQAinHdUIOe6osNlpxMFXwfXJS6XEc6 3T6PHm7DC9KaV6wLALEpASqZjAllcog87rGyStN6QhBnr0E13nDe4xwWaehohUlGlPZG 7WxAzHBvgAkJdykdEsjtKmYe75cndKm1WPrSYI8nU4+P5NWfaaPBVnkpoNZruTQY8xlq mYOXHxha078tz0QihctSBf3zpkQR+b2U+DZwbFu3dTdSBIRzLhPZYcz/c73UoM9hb/tE U67ciOSJ+ZMxpZ/vW5CjcBCzdXVFUuDMyefzY3BkoqThbOn05y2nXLs6Z9DZTSr2mAYR mpoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1755594539; x=1756199339; 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=b7GQRkJjLj0j3dNMqeMnq8zCLevsX26SkayOg/7wVlQ=; b=AyZxWgVFJqs+VZEEnrGKTITGpU6L3T1uz5VHst79SiWVD6BXvLcv8LIK7jOWkKE4Bj NyVaZ/j72p+7fDG3bpvhSl2T272JRqUvhVyQERYq99Ml10hIIg/4vQUwnRumvKE4BLkO 6WD1ylpgW8mW0Viy/IM9ASryPVBtCljDYEO9Jvb2qK5g9tZM/afzFVTnGdQ801OdaP9X LZeaB18QqL14oWBkOR+/6sBipz5WxGo6H+aQ1jUCk9MpRj6yWGCkntre6Q9tyn1I9Ayr DugtbDhEd6TBEnVIrGHwRNwIsketDkA8T72UFnmQnhHNw2b/HL+mjKaECaNQu1QWsHxt TXug== X-Forwarded-Encrypted: i=1; AJvYcCXOrIZqqs680FiegK8JM3Z/KFhdZwkeCCgn7YzXd2v/N6UbGF4uFoxxj9O+bP0K6K/y+Hmsqv47MPTPtxM=@vger.kernel.org X-Gm-Message-State: AOJu0Yzge3AfLpR3189aYxiQM3oWSL/3PokbW7FdabLLeawoteuOFSwT UVgMuE0iCqHtDauDnTE/c4/5x4XIdKU+PYR4awi6QUqMCCPxvYJnMFUwMpDYCSMOMUQxdYgm/wz LKg== X-Google-Smtp-Source: AGHT+IEl+5DEbXQSzekfCwJnh9tAA1jzlM78/0IsLI3MJWSPRp03wLItZPI7GL4eVRBnoTBswnyDHI1oMA== X-Received: from wmbeq12.prod.google.com ([2002:a05:600c:848c:b0:459:db29:1efa]) (user=keirf job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4f12:b0:459:e3a1:a0c4 with SMTP id 5b1f17b1804b1-45b46190a32mr1402635e9.30.1755594539541; Tue, 19 Aug 2025 02:08:59 -0700 (PDT) Date: Tue, 19 Aug 2025 09:08:51 +0000 In-Reply-To: <20250819090853.3988626-1-keirf@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250819090853.3988626-1-keirf@google.com> X-Mailer: git-send-email 2.51.0.rc1.193.gad69d77794-goog Message-ID: <20250819090853.3988626-3-keirf@google.com> Subject: [PATCH v3 2/4] 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: Sean Christopherson , 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 3f207b5f80a5..ccccb5c04ac1 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -562,7 +562,7 @@ 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); @@ -593,14 +593,7 @@ 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 2.51.0.rc1.193.gad69d77794-goog