From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 E198C2D29C5 for ; Thu, 22 May 2025 23:52:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747957963; cv=none; b=rF5oSLZwx0DfOM3b9cmYmFBKDLeVN5h1yoTST9+KKk/v81ilPMPLzpI40JWBgl41AVgObINzwBwXHgZgj4j0RHYGyTub3FFGWjOoVzzpRNFxBUQCn7s+L6onEMNhAmJ0B9cgbXEsnGpFZN7TeytiX2w0SjemiIHyWFUkD5ZLtIs= 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=209.85.215.202 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-pg1-f202.google.com with SMTP id 41be03b00d2f7-b26fa2cac30so4426800a12.2 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=v1zEzCbRfizOOl3eg6v9L6YhC3QETpCNWVOhADbimFmghEOc+rO+3LL0OqkPNzbq6y g+R2UKj2wr43cFQn5GkKJ9RP87oeGW/dzjtXxbC5gYBlNXeVc1SY7Q5ZMQfvSR37kEad +2Tari1Bqpfq56fsUsRR9dbp45bnm8hRbi3PUeg68T9nvLZIisdvYXJoy9sDcyys7//+ TtO6YJB7vuClYJnyTWI11bvqID9mYOdR3IeTVvhljxCXs72jOQq1yHOk8T9dx49s/bou KY68I4FYhN8jWwCZcKW4esSEQUj7DVtDR08j5YpOZZQjxm1+oED3/XCR2JAcNjL1qtYp PGbA== X-Forwarded-Encrypted: i=1; AJvYcCV4SlWBdWcXz7kqhfSntNA4e9Vnpif5CxUoC/yvhJN4n7+QmE5dL7WnyUnipHv94GpHpiEtMMpx4VniYHpg6Ko=@vger.kernel.org X-Gm-Message-State: AOJu0Yz8wGe8SmIEMu14MhBItC3DxjfPZl+sggqf59WS10lh7pJRBLnA H8iFwFbjTpzNYrgbW4SS1l5XmyOV569A3aLA9LXn2rj/1fALLbjm5/mCdZN3IhWkreaLsPPdF1O wwjJsog== 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-kselftest@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-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; } -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 = container_of(pt, struct kvm_irqfd_pt, pt); - struct kvm_kernel_irqfd *irqfd = 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; + lockdep_assert_held(&kvm->irqfds.lock); + n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi); write_seqcount_begin(&irqfd->irq_entry_sc); @@ -286,6 +266,49 @@ static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd) write_seqcount_end(&irqfd->irq_entry_sc); } +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 = container_of(pt, struct kvm_irqfd_pt, pt); + struct kvm_kernel_irqfd *irqfd = p->irqfd; + struct kvm_kernel_irqfd *tmp; + struct kvm *kvm = p->kvm; + + spin_lock_irq(&kvm->irqfds.lock); + + list_for_each_entry(tmp, &kvm->irqfds.items, list) { + if (irqfd->eventfd != tmp->eventfd) + continue; + /* This fd is used for another irq already. */ + p->ret = -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 = 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 = NULL, *resamplefd = NULL; struct kvm_irqfd_pt irqfd_pt; int ret; @@ -414,32 +437,22 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) */ idx = srcu_read_lock(&kvm->irq_srcu); - spin_lock_irq(&kvm->irqfds.lock); - - ret = 0; - list_for_each_entry(tmp, &kvm->irqfds.items, list) { - if (irqfd->eventfd != tmp->eventfd) - continue; - /* This fd is used for another irq already. */ - ret = -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 = irqfd; + irqfd_pt.kvm = kvm; init_poll_funcptr(&irqfd_pt.pt, kvm_irqfd_register); events = vfs_poll(fd_file(f), &irqfd_pt.pt); + + ret = irqfd_pt.ret; + if (ret) + goto fail_poll; + if (events & EPOLLIN) schedule_work(&irqfd->inject); @@ -460,8 +473,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) srcu_read_unlock(&kvm->irq_srcu, idx); return 0; -fail_duplicate: - spin_unlock_irq(&kvm->irqfds.lock); +fail_poll: srcu_read_unlock(&kvm->irq_srcu, idx); fail: if (irqfd->resampler) -- 2.49.0.1151.ga128411c76-goog