From nobody Fri Oct 3 01:08:47 2025 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) (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 91D5A3148A2 for ; Tue, 9 Sep 2025 10:00:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757412019; cv=none; b=d+dA5aMyM1iA3nrd6mFJ2uOAfshJ6gzxkk+Fqcoacke/dq6EDI+TIm3Lqjet4kv3hPkhg7ZQF4WZfJr2lPMQ/fwra67wP+kr/eTuIFVIYjJeO6r2kUNNnvbw4coQu24Z95UWfeEBb57jKqUqU+MIfz5QikDc9P+fYUaUrrw0d+8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757412019; c=relaxed/simple; bh=C65JVKMfdNUvB842mIc5ZPEsMCIkTNLE2L0PO540/+4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=K84zetCEBkWxmghuOR+9lbzn9TpdawnyrSOUcqs4Mccfjj86uXodMspZRF7C6tkm9eSdH6/Z2yuzURktlbIjodElUHbYvhVsycgTlMDYebUG+W8pih1E0vnh9VhP16O/zxKyl1EFhIMHz7yjbAOVnFMngXyn0LUHaxH2YKIoicw= 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=CXTk7AZy; arc=none smtp.client-ip=209.85.221.74 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="CXTk7AZy" Received: by mail-wr1-f74.google.com with SMTP id ffacd0b85a97d-3e40057d90aso2057926f8f.0 for ; Tue, 09 Sep 2025 03:00:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1757412016; x=1758016816; 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=t2APtNHHyxo533cskw92lxdMihs7PuU7RV34cw5AXBI=; b=CXTk7AZyFh2F/Oau567Cj/+Jc6Wtk50lJsVP0MKO1MADRt8msngzQ5zeVA9g4OY8VB /ZIJkiVpZBa6r/IoEtj14iweB9CtUpW4U97bZLSxaX1LI3VHMjHnEZjbsvVzkkG3JDP1 gR9bejYmga3twp2lLzuDT1fgVQWyEEebUEsrlcRaV3SxcQdPSuukCEtshK06uMZqw69r 0VvlgOSpubCfWXPIKcr0xx4qcTOBccUucrbNv9XwTZbBYsWWMTBNJ/4NxQfaYpKW5qCx QZ0A0AViFLaLOmvtXMIfXMe0pGZguKvj/hM4lKWPVUjm2K6HLiEhnpv8zZ7b6NikuRxj 7rZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757412016; x=1758016816; 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=t2APtNHHyxo533cskw92lxdMihs7PuU7RV34cw5AXBI=; b=RM0dumKJlXngl5otJEeOq1XNG0h0v5MmPRZ5l2YHX8xcX0GXoo5if/uYK98mDEmCld tIpsJmosjsCzu/3zmAwsYSQfZaN+IQbGVZHK1TFHFZtsuDumzzmzSoxp1HPy3MxIpoDO 740dDB7t5bzJNAs/hE0y5YSmQ4O/RSz8wbHKwWoPd3GRWUsFLyG4KeEFDyRX3Dz6pQTI 3vU0b7nkitEC5NYOjQMR0xpJ9AloXQwkE5rkmzaD7L5tN7eLqVDAKo82RZhA9Cy/CMaP 27vjhLrxPIXRTaXD41dS+wQrZhEmN8bBv0BC6fkod7EfyfLMJCJy+KKVwN/KXl280a3/ MnEw== X-Forwarded-Encrypted: i=1; AJvYcCXlQvf4CNxmFFRpJpodgx8R9HVrRlPhvyDzLMSA7c8aR2UKUXEEdbfhkjKF2OuRfAMtLv2L745/qFHakHg=@vger.kernel.org X-Gm-Message-State: AOJu0YwEL8i7uyI2vJg/SBhQE7Eztitov/4K9xgY1s+NEEJlklBaazfa KLEk8hnCg4uzKASrOnLt3qnkMU+v4gWTkExJRQJvwVTYdf4XfQhibQYT8wjRwcIB4JXtxacNkQQ VVg== X-Google-Smtp-Source: AGHT+IEaeuL7yLD0zJ6dVDDu1CnL/lrOdGiAdKs9KWet1I8AXuefzYo8TDKeImXKCQUtFMCZRXRSbCKA3g== X-Received: from wmbbi7.prod.google.com ([2002:a05:600c:3d87:b0:45b:885a:402d]) (user=keirf job=prod-delivery.src-stubby-dispatcher) by 2002:a5d:5d13:0:b0:3e7:481d:7a6b with SMTP id ffacd0b85a97d-3e7481d7f17mr6380076f8f.10.1757412015873; Tue, 09 Sep 2025 03:00:15 -0700 (PDT) Date: Tue, 9 Sep 2025 10:00:05 +0000 In-Reply-To: <20250909100007.3136249-1-keirf@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250909100007.3136249-1-keirf@google.com> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250909100007.3136249-3-keirf@google.com> Subject: [PATCH v4 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 2.51.0.384.g4c02a37b29-goog