From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) (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 C139238399C for ; Tue, 4 Aug 2026 18:51:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785869480; cv=none; b=DmooWQIdAI/Vev/UL3BPojcs/ZS36D0CYqyiNiQexsIu/JPcBUROdiyMWj7WHd68O8W0UmHoAFDZd8iXuREhAuhPb8c9zwIiSSm1itXOwX7Y0vLLOPKSNK9HtY7TdUbiCtlrWtWAJKtrJC3PjFRjBJRSxrD149klmb76oS2BhPQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785869480; c=relaxed/simple; bh=86B3BBLW8NnxL8U0IAZgS6A8MjKZ1A/OLEY6LvzwoLU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=l8s+1BXlrX4OenPAM9oGXvykHYKs7LIw19y9GyUV6xGRLUq+/5moTO1EuiTQUbMrEZ41N0q5wI8Pyi+0eewZIsZ4ww+4r3OVNUDXt8AKTG/M9yNvgM90bEcv9FSJlfPGC8ovcS6NvIXDnR3q2WaaKrP5ylqkgV1MudeMiT63yvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--praan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=IyubcPC1; arc=none smtp.client-ip=209.85.214.198 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--praan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="IyubcPC1" Received: by mail-pl1-f198.google.com with SMTP id d9443c01a7336-2ce7dff6253so11961745ad.1 for ; Tue, 04 Aug 2026 11:51:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785869475; x=1786474275; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=t6VEXazL8yheZxsIS8BkIrSzpg52BXjB99hyFiWVn2Y=; b=IyubcPC1lYxmgzhckYH+EPszSFP/J5UjnfqJVucRYaJ768WAPgWL6DciZ19cRwqYg3 IOSAb3Ea2v9H3OwUG8xd7FyoKubDWyz4UJoeNCf2ErjkbOXd7hU4d8lI2OflKyldxWxW r9iRPvd9j1GoezGYssYhwEs4oEQgDBrHvgypHaWXC1ADSktmJptidD5MfeFVyj3y73Qo yAF5cbSAOJzBkteyqcYly9g1VNin2bvgCF2SDqTlfKr/RLOk0hdF/AnqCBkfD8bESe2y cGKzs3yCPNblQlQltmSDNvsQP90hwGOG/7zpvNZeFA3ZUkNbBCMQ6ztSKy2nyqCT3XpC pC6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785869475; x=1786474275; h=content-type: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:content-type; bh=t6VEXazL8yheZxsIS8BkIrSzpg52BXjB99hyFiWVn2Y=; b=pBNQV0kMukH3/2iciy1CHnuVDz79fapwkwEWR1Og2DJ1iYM5uhfDAp9DrBUFZTYREe ER0Dsq4wTtZF5CIrPcn26Zh6nCXZn6c0TvtlFOPlcAGeF5fCl1+a2af5CckgfM26yj2B 0qJrOVUNbxyL9ms5n72oFQ8Qf8//Hrmqr/4K30tZvJzjQBkArw3xB48rypOhHliTX60n WzUB609viECd5VawZadDoWcBuD46e/KMbLdz3G8CtRqtA8Q0PvGR/082IjlswCrbgocT P8b1d8C4yowbVyeKwNGDfkKz52YC9Dkw4xY7lgHPE49CcmxnT9kG892DoeaTAuteFm8d 338g== X-Forwarded-Encrypted: i=1; AHgh+RqWUgW51H29gRHsdrpKn2HcdsKize4bPlhxjVgFnT4ed3Z9xQnuLDazwheo0OtQqpgjswE=@vger.kernel.org X-Gm-Message-State: AOJu0Yxz47RnQJXmf4CgNyZ9ouNxZwEuRJNPIPD2Ezp4nJVzoq0geaRE DB77EkH1Cny04RsdUgFU8TpivI4E8x6ybf5+fG9ABigWIoX/4EgYOdsjn4xbfH7FqIxCMOh2Png 9UQ== X-Received: from plbke7.prod.google.com ([2002:a17:903:3407:b0:2c6:a078:41f8]) (user=praan job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2c08:b0:2cc:bdb9:3c04 with SMTP id d9443c01a7336-2d08ab5dc5cmr53683795ad.17.1785869475101; Tue, 04 Aug 2026 11:51:15 -0700 (PDT) Date: Tue, 4 Aug 2026 18:50:49 +0000 In-Reply-To: <20260804185050.2053672-1-praan@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260804185050.2053672-1-praan@google.com> X-Mailer: git-send-email 2.55.0.571.g244d577d93-goog Message-ID: <20260804185050.2053672-5-praan@google.com> Subject: [RFC PATCH v2 4/5] vfio/pci: Add .mmap handler for page-backed DMABUFs From: Pranjal Shrivastava To: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Bjorn Helgaas , Logan Gunthorpe , Alex Williamson , Jason Gunthorpe , Kevin Tian , Pranjal Shrivastava , Ankit Agrawal , Matt Evans , Vivek Kasireddy , Leon Romanovsky , Shivaji Kant , Samiullah Khawaja , Unnati Sachan Content-Type: text/plain; charset="UTF-8" Implement mmap and a corresponding page fault handler for ZONE_DEVICE backed DMABUFs. Set VM_MIXEDMAP for page-backed VMAs and introduce the vfio_pci_vmf_insert_page() helper to insert struct page pointers into the user PTEs. Signed-off-by: Pranjal Shrivastava --- drivers/vfio/pci/vfio_pci_core.c | 39 +++++++++++++++++++++++++++--- drivers/vfio/pci/vfio_pci_dmabuf.c | 22 +++++++++++++++-- include/linux/vfio_pci_core.h | 3 +++ 3 files changed, 58 insertions(+), 6 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 9ca99a5a61c3..f5c2912c3ffc 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -1790,6 +1790,34 @@ vm_fault_t vfio_pci_vmf_insert_pfn(struct vfio_pci_core_device *vdev, } EXPORT_SYMBOL_GPL(vfio_pci_vmf_insert_pfn); +vm_fault_t vfio_pci_vmf_insert_page(struct vfio_pci_core_device *vdev, + struct vm_fault *vmf, + unsigned long pfn, + unsigned int order) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page; + + lockdep_assert_held_read(&vdev->memory_lock); + + if (vdev->pm_runtime_engaged || !__vfio_pci_memory_enabled(vdev)) + return VM_FAULT_SIGBUS; + + /* vmf_insert_page only supports 0-order pages */ + if (order > 0) + return VM_FAULT_FALLBACK; + + if (WARN_ON_ONCE(!pfn_valid(pfn))) + return VM_FAULT_SIGBUS; + + page = pfn_to_page(pfn); + + if (vma->vm_flags & VM_WRITE) + return vmf_insert_page_mkwrite(vmf, page, false); + + return vmf_insert_page(vma, vmf->address, page); +} + static vm_fault_t vfio_pci_mmap_huge_fault(struct vm_fault *vmf, unsigned int order) { @@ -1877,11 +1905,14 @@ static vm_fault_t vfio_pci_mmap_huge_fault(struct vm_fault *vmf, vmf->address, order, &pfn); - if (pres == 0) - ret = vfio_pci_vmf_insert_pfn(vdev, vmf, - pfn, order); - else if (pres == -EAGAIN) + if (pres == 0) { + if (priv->zone_device_backed) + ret = vfio_pci_vmf_insert_page(vdev, vmf, pfn, order); + else + ret = vfio_pci_vmf_insert_pfn(vdev, vmf, pfn, order); + } else if (pres == -EAGAIN) { ret = VM_FAULT_FALLBACK; + } } } diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c index b936da3bcada..b582e856ba7a 100644 --- a/drivers/vfio/pci/vfio_pci_dmabuf.c +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c @@ -4,6 +4,7 @@ #include #include #include +#include #include #include "vfio_pci_priv.h" @@ -53,8 +54,14 @@ static int vfio_pci_dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct * vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); /* See comments in vfio_pci_core_mmap() re VM_ALLOW_ANY_UNCACHED. */ - vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP | - VM_DONTEXPAND | VM_DONTDUMP); + if (priv->zone_device_backed) { + /* VM_MIXEDMAP is required for ZONE_DEVICE pages */ + vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_MIXEDMAP | + VM_DONTEXPAND | VM_DONTDUMP); + } else { + vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP | + VM_DONTEXPAND | VM_DONTDUMP); + } vma->vm_private_data = priv; vfio_pci_set_vma_ops(vma); @@ -521,6 +528,17 @@ static int vfio_pci_dma_buf_alloc_struct_pages(struct vfio_pci_core_device *vdev if (ret) { if (ret != -EEXIST) return ret; + } else { + /* Initialise the refcount for the freshly allocated page. */ + unsigned long pfn = pci_resource_start(pdev, bar_index) >> PAGE_SHIFT; + unsigned long npgs = pci_resource_len(pdev, bar_index) >> PAGE_SHIFT; + + while (npgs--) { + set_page_count(pfn_to_page(pfn++), 1); + /* Yield the CPU periodically on large BARs to prevent soft lockups */ + if (unlikely((npgs & 4095) == 0)) + cond_resched(); + } } vdev->p2p_struct_page_bars |= (1 << bar_index); diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index c28f06bae302..778671194b24 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -187,6 +187,9 @@ ssize_t vfio_pci_core_write(struct vfio_device *core_vdev, const char __user *bu vm_fault_t vfio_pci_vmf_insert_pfn(struct vfio_pci_core_device *vdev, struct vm_fault *vmf, unsigned long pfn, unsigned int order); +vm_fault_t vfio_pci_vmf_insert_page(struct vfio_pci_core_device *vdev, + struct vm_fault *vmf, unsigned long pfn, + unsigned int order); int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma); void vfio_pci_core_request(struct vfio_device *core_vdev, unsigned int count); int vfio_pci_core_match(struct vfio_device *core_vdev, char *buf); -- 2.55.0.571.g244d577d93-goog