From nobody Fri Oct 31 16:24:01 2025 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 9128E2D29C8 for ; Thu, 22 May 2025 23:52:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747957963; cv=none; b=pCzunnQMDQ/S+ig3UDtpZz4r7iQ/5nzeGwUAOHGSkm/R+5Ql/zOUER0Z1nKfDz1p/ha5U427SUaagNY5JdwUtNTyxaspEJZeuA1v4AjtF+EioLLOSwfxuwO6lL/qpS8lbtnrsIAE8OfKO9UTPrIbNEpJ4RekvBiaKAbKF5juLks= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747957963; c=relaxed/simple; bh=nT3odiErLVUjr4YXPHw8YhTvO26ovL3HqyGLIpyXkAw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=c28EyFJpiK9V8tSER9dhcKNLwmz47TVF0d+DtP/7eoPelRmsNSxq2YMavdlvRgqJKHJVRSVZ3cBdd0RlTE/p6VkbUMB70C+hcCb7UCLmKNR+OOQEjao/okEAo3BCUAMk8PQmGY7MtTfs2zfCXdB077e//2lfp04tisxH3+QW+0A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=eovY5jLw; arc=none smtp.client-ip=209.85.216.74 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eovY5jLw" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-30e74ee960aso6798036a91.3 for ; Thu, 22 May 2025 16:52:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1747957961; x=1748562761; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=f7qvTnT5s0mxP5eCWb+NaTk8UKR3m+k6rkKzLbxKznI=; b=eovY5jLwTZBzafMvxLtrWra3lxyOdBwWHD0QRUUea824sSYRnBVpT9a5kgIe1KXYdh SV2En2eE45AJ8YXaT9u4IynsOcNDTScCCYWNJKFxX38gFecfEQyS9m00d4PM2pWW55nb crsLSCcMt/JqPvMfVI8hbp5XbJPGI0kbjrdeO6QCEubTYo7NVW11mRgKH4mOrMndhpre WddrFT/YJOJMMoRsFVGtknJAHTcymBm1dcM3T7PnnbF0Df5k8qSsEqEE1E8JOCaA7OvF CuqriDI8iohzR3/KGKiV1v+gVkABjaq8pQPrb5HSx76xYsOV6GMh5xyiTXFgmwzTWXJe k+Cw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747957961; x=1748562761; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=f7qvTnT5s0mxP5eCWb+NaTk8UKR3m+k6rkKzLbxKznI=; b=V/S5RR4mZVw9PWBmmNVPGU4+PUHKCVpC7Y2aMYJu9TzHZbhipLIfkcJ4K/pe9fRC0j ZezCY4/cUDnEZRGbvKepuMPRTC+jDXcK0I7Szv66B5GuExycS7x1eb1K4bdhkJGkmPGi wwTNFPSI/szGRtLW44ilgqf2YglFknd7p667MHD82D1GHAHGKo5u3czIw3A9UCSQwIMF vVK3iMba9w3AW/hCa/C68TrloJDUuzgOcF7DRS26eE8+cjAmLTzTCyBmJaZTdkzaRHcF AsmHknVQIj5B9WHGkXLoPse0f1egqYLnYJc66A+uIPNDwC8KpQ+tJO8ezn78zzhDWwoF Sy0w== X-Gm-Message-State: AOJu0YwRg7msvAjNP9DCR+8i6VPVds/v4mzgtnTLgnZxKUb685tios4G b8raBdWNnulhuzhKgCpuCiUgvMroiZKmTsPmfU1xAcWhQJoDukt4siS++aFMSr9Buwf2oTe/7KA 4w7J8+w== X-Google-Smtp-Source: AGHT+IFhLIWMr3ct7tle+BqkfXynUt92dE5T1Ga0fMI6fA92WD5PFOynQ9QIYOuFaunMobUQi3Ht7v2BK94= X-Received: from pjbsz13.prod.google.com ([2002:a17:90b:2d4d:b0:30e:7d59:f3a7]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:dfc7:b0:301:c5cb:7b13 with SMTP id 98e67ed59e1d1-30e830c6247mr35762810a91.3.1747957961111; Thu, 22 May 2025 16:52:41 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 22 May 2025 16:52:14 -0700 In-Reply-To: <20250522235223.3178519-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250522235223.3178519-1-seanjc@google.com> X-Mailer: git-send-email 2.49.0.1151.ga128411c76-goog Message-ID: <20250522235223.3178519-5-seanjc@google.com> Subject: [PATCH v3 04/13] KVM: Add irqfd to KVM's list via the vfs_poll() callback From: Sean Christopherson To: "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Juergen Gross , Stefano Stabellini , Paolo Bonzini , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Shuah Khan , Marc Zyngier , Oliver Upton , Sean Christopherson Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, K Prateek Nayak , David Matlack Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add the irqfd structure to KVM's list of irqfds in kvm_irqfd_register(), i.e. via the vfs_poll() callback. This will allow taking irqfds.lock across the entire registration sequence (add to waitqueue, add to list), and more importantly will allow inserting into KVM's list if and only if adding to the waitqueue succeeds (spoiler alert), without needing to juggle return codes in weird ways. Signed-off-by: Sean Christopherson --- virt/kvm/eventfd.c | 102 +++++++++++++++++++++++++-------------------- 1 file changed, 57 insertions(+), 45 deletions(-) diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 8b9a87daa2bb..99274d60335d 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -245,34 +245,14 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode,= int sync, void *key) return ret; } =20 -struct kvm_irqfd_pt { - struct kvm_kernel_irqfd *irqfd; - poll_table pt; -}; - -static void kvm_irqfd_register(struct file *file, wait_queue_head_t *wqh, - poll_table *pt) -{ - struct kvm_irqfd_pt *p =3D container_of(pt, struct kvm_irqfd_pt, pt); - struct kvm_kernel_irqfd *irqfd =3D p->irqfd; - - /* - * Add the irqfd as a priority waiter on the eventfd, with a custom - * wake-up handler, so that KVM *and only KVM* is notified whenever the - * underlying eventfd is signaled. - */ - init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup); - - add_wait_queue_priority(wqh, &irqfd->wait); -} - -/* Must be called under irqfds.lock */ static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd) { struct kvm_kernel_irq_routing_entry *e; struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS]; int n_entries; =20 + lockdep_assert_held(&kvm->irqfds.lock); + n_entries =3D kvm_irq_map_gsi(kvm, entries, irqfd->gsi); =20 write_seqcount_begin(&irqfd->irq_entry_sc); @@ -286,6 +266,49 @@ static void irqfd_update(struct kvm *kvm, struct kvm_k= ernel_irqfd *irqfd) write_seqcount_end(&irqfd->irq_entry_sc); } =20 +struct kvm_irqfd_pt { + struct kvm_kernel_irqfd *irqfd; + struct kvm *kvm; + poll_table pt; + int ret; +}; + +static void kvm_irqfd_register(struct file *file, wait_queue_head_t *wqh, + poll_table *pt) +{ + struct kvm_irqfd_pt *p =3D container_of(pt, struct kvm_irqfd_pt, pt); + struct kvm_kernel_irqfd *irqfd =3D p->irqfd; + struct kvm_kernel_irqfd *tmp; + struct kvm *kvm =3D p->kvm; + + spin_lock_irq(&kvm->irqfds.lock); + + list_for_each_entry(tmp, &kvm->irqfds.items, list) { + if (irqfd->eventfd !=3D tmp->eventfd) + continue; + /* This fd is used for another irq already. */ + p->ret =3D -EBUSY; + spin_unlock_irq(&kvm->irqfds.lock); + return; + } + + irqfd_update(kvm, irqfd); + + list_add_tail(&irqfd->list, &kvm->irqfds.items); + + spin_unlock_irq(&kvm->irqfds.lock); + + /* + * Add the irqfd as a priority waiter on the eventfd, with a custom + * wake-up handler, so that KVM *and only KVM* is notified whenever the + * underlying eventfd is signaled. + */ + init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup); + + add_wait_queue_priority(wqh, &irqfd->wait); + p->ret =3D 0; +} + #if IS_ENABLED(CONFIG_HAVE_KVM_IRQ_BYPASS) void __attribute__((weak)) kvm_arch_irq_bypass_stop( struct irq_bypass_consumer *cons) @@ -315,7 +338,7 @@ bool __attribute__((weak)) kvm_arch_irqfd_route_changed( static int kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) { - struct kvm_kernel_irqfd *irqfd, *tmp; + struct kvm_kernel_irqfd *irqfd; struct eventfd_ctx *eventfd =3D NULL, *resamplefd =3D NULL; struct kvm_irqfd_pt irqfd_pt; int ret; @@ -414,32 +437,22 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *a= rgs) */ idx =3D srcu_read_lock(&kvm->irq_srcu); =20 - spin_lock_irq(&kvm->irqfds.lock); - - ret =3D 0; - list_for_each_entry(tmp, &kvm->irqfds.items, list) { - if (irqfd->eventfd !=3D tmp->eventfd) - continue; - /* This fd is used for another irq already. */ - ret =3D -EBUSY; - goto fail_duplicate; - } - - irqfd_update(kvm, irqfd); - - list_add_tail(&irqfd->list, &kvm->irqfds.items); - - spin_unlock_irq(&kvm->irqfds.lock); - /* - * Register the irqfd with the eventfd by polling on the eventfd. If - * there was en event pending on the eventfd prior to registering, - * manually trigger IRQ injection. + * Register the irqfd with the eventfd by polling on the eventfd, and + * simultaneously and the irqfd to KVM's list. If there was en event + * pending on the eventfd prior to registering, manually trigger IRQ + * injection. */ irqfd_pt.irqfd =3D irqfd; + irqfd_pt.kvm =3D kvm; init_poll_funcptr(&irqfd_pt.pt, kvm_irqfd_register); =20 events =3D vfs_poll(fd_file(f), &irqfd_pt.pt); + + ret =3D irqfd_pt.ret; + if (ret) + goto fail_poll; + if (events & EPOLLIN) schedule_work(&irqfd->inject); =20 @@ -460,8 +473,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *arg= s) srcu_read_unlock(&kvm->irq_srcu, idx); return 0; =20 -fail_duplicate: - spin_unlock_irq(&kvm->irqfds.lock); +fail_poll: srcu_read_unlock(&kvm->irq_srcu, idx); fail: if (irqfd->resampler) --=20 2.49.0.1151.ga128411c76-goog