From nobody Tue Oct 7 02:15:47 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 9EDFA2F3C3E for ; Wed, 16 Jul 2025 11:07:47 +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=1752664070; cv=none; b=r9ssUCYkvTU6eFcj6pb6EJWWGrFv497/uX7YAQUXt7acfFtLLM6pYmHCDdBSmRyYYmf6m3Q+ZPJtiWeI0rA4/wGf28hS0Dg+eYaY9Z2quHHEFjHY7BCjvvkAuILyTmTTLsjs0xE6Dfk0ymYLtdAezvAnEvE5zokPyrCG/U5Phbw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752664070; c=relaxed/simple; bh=PrPZi9FLkMWKmIdJSQLq3BcigSFeFqZOp9S9N0GiAU8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=izI9vTEzQ/5yepsRmH1VbLclsWCHz66oxe+JSgoTcetVcVrt/B+bKzUJoEM4INmFTHq6ZG8mnqHJ/PRjd3imzOKs7os71rh6JMMRYzdYPgAKy8HS7HNu6CVw1XUhyxV4g5M1MbQvUM3E1zoSKFJExl/uLRezc0yGiNyk7u0XCsA= 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=QZ3BZ3oU; 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="QZ3BZ3oU" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-454dee17a91so50627445e9.3 for ; Wed, 16 Jul 2025 04:07:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1752664066; x=1753268866; 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=Hxqszaeuljrqlm0t8DgnPuG7w9pgNEhhBTVGlWt0Bfs=; b=QZ3BZ3oUkA5fkjLHPoQ7w9WB+U8mzCKcAEeN0r8Iyqav47Z++28pidd4psSSn/x8V4 poA1PNJO9vGFIzQEGMey0jzvcgnsMnAsiaxZybhVZPKqAPJldexQNKA8MBKjxcrvYxm9 zCN5m5sNokork1u9xiDzhF23F0cNV/zX2xEzLZmjAK5hBC90emprwHkoJWtiZWrhahv9 U4mj3AXpurSCJiI6lyoKrTyxUuNJUVhuTXYVNA/oYZsznxg5Zzr1HCkCyrOAg9BkiRvT e88onoQZYFS3OWSmk1HvkklD6L/PGLg6gHNCWz+wcYYXj/3V5GcHwNfwRMoGba9RpoBF ibng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752664066; x=1753268866; 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=Hxqszaeuljrqlm0t8DgnPuG7w9pgNEhhBTVGlWt0Bfs=; b=C6uk8Cv62ttx5JQYNqzcGLI4Q8yrAVlHYNontZvF9LNT5eSOr9CHr/ClqI4E0A9j40 jwSuq2G9mmL2q5cRkrNReDazgWSyruTanGb7N82HP1akPiZMQ2rCptLwtI2yi/nALGfL m5xt1Do+eiCO/RFjIa+JagXgnRb5dQWSIDANkU2dLLzEDUAvKk2dXANCBNJ4N7DcWmtU 5P8IuFfcaL6rql+6d1bURZswzddLRi75iFNQfaocnnQ/FkjD1FaQRmEKE8cpBlDHUqh1 6srDbuEfsi6xixnY+w+vvTMx8UlA7NJufZcekiTTvUlrl8C10gnaGUN/wvT2t8MBTxxX tfqQ== X-Forwarded-Encrypted: i=1; AJvYcCUdx53uKw4lud3SmLAonDu8Odf1Tp0Q+/CVVBT5R+fIBdQWgoOpNy37R9iIDgRMkY+LzBDQ42Gfv0JAnFc=@vger.kernel.org X-Gm-Message-State: AOJu0YyGSKdA49BQQKQJ5bN06TOUwBPdT5DWtuFmzGystkfhvizrR6LU lJn0XzHqLjuXL5cyh0IbfpTAGoUZCEu3VjgekocJaHjvCl5omlYtjDkoZnNdHd/3csES7Ouplp7 l5A== X-Google-Smtp-Source: AGHT+IEc90RI4GCOsQRZO8PqFs/HKd6dYrEM+oA0RTzrbntMXuFw8OS9F/kKOUPw5mrVP3l/ZU5GEG7EJA== X-Received: from wmqa10.prod.google.com ([2002:a05:600c:348a:b0:455:76a8:b3a]) (user=keirf job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:5299:b0:456:1c4a:82ca with SMTP id 5b1f17b1804b1-4562e3c227cmr18678235e9.32.1752664065812; Wed, 16 Jul 2025 04:07:45 -0700 (PDT) Date: Wed, 16 Jul 2025 11:07:35 +0000 In-Reply-To: <20250716110737.2513665-1-keirf@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250716110737.2513665-1-keirf@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250716110737.2513665-3-keirf@google.com> Subject: [PATCH v2 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 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 2.50.0.727.gbf7dc18ff4-goog