From nobody Fri Oct 10 15:55:17 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6F0771C84A6 for ; Fri, 13 Jun 2025 13:41:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749822090; cv=none; b=ds+qA00adsD40KbVoljSLICOM6glR8RNbSrG+rmYX2/TNJnQs29bOwYG/EnjR0TH6jKgKvCVZmYrIgD7PqHFpHOc6zYRb+AJXvygCQaxhU5Zthz5Vm9NZHM/6S7XAVCMHs3BpGiIg6TbnxP9XBgpk2tdmx2JgXV8c3k2gwNwfB4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749822090; c=relaxed/simple; bh=/Hj2o0NKvMzVIjNKTfgbctNmnmS2OLsACrglt6/q3Wg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c99i6SDWy+xMRGCV9P3s5z+i5rHFdLwc4KyTrF+Qf0SEMEn1wKxn7GF4FIkmuDGbnqCKLkbqrD2RAtFT5OttHSMxq0kojZq+Ezlm/1Lg+O3GogjQJXGkldLrJeYfcVZBLNkDbezlm2y1zesQ01NOmMy2MoUD7om6XzXemNpjFDc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ZfCuYgeM; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZfCuYgeM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1749822087; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1Rg4eLLEgx6FDFHzHNf6mLR85Vz7bTkf4DxmFxHRoP8=; b=ZfCuYgeMNZ5rlCEGHfvR5+089zXLLFvmoUujnRc+4SaUyJr9OFZu2RZV7aRDYy6XK5j8rv MamZT8XLNbScf8PML+w1e/NIpg0oDH5QGJdQ/M5rFcV3ZY+AhoL7nyLUmZ1S5nsol2rqOQ o+iQ6NmP8Geuau+fMBJGXH+XFEeCsdc= Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-692-PQMQZBN9MWOzi7p0GDseqg-1; Fri, 13 Jun 2025 09:41:26 -0400 X-MC-Unique: PQMQZBN9MWOzi7p0GDseqg-1 X-Mimecast-MFC-AGG-ID: PQMQZBN9MWOzi7p0GDseqg_1749822085 Received: by mail-qk1-f198.google.com with SMTP id af79cd13be357-7d2107d6b30so328121085a.0 for ; Fri, 13 Jun 2025 06:41:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749822085; x=1750426885; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=1Rg4eLLEgx6FDFHzHNf6mLR85Vz7bTkf4DxmFxHRoP8=; b=nhuVQPielATYPvVAcNTmV5lN3hzumqd2aTinZemJLvLgZSu/rAJdKwGvlsn/jBxQZN 3RmxuhkaeBraK+kHOvwaO7ymkbb0wFQKci06XSJKjctOnyzZCcCWkk5WddKIwbTlma60 V1ia91Vn/RQJIO7rGzS2TXV7MO+OY1CJmXqSldZrNfSAP342ZZvKQbRQC93lSm5+Sv1A mgHtIOEjwbtRBljRF2RKJKUcSVDI3kirIUCUL4YErKF/wEYc66PRnCbqetdyRAzuCjgY wtdU1yiJNUw5gz17DYlENHVOtI4ZQub//wuKI4CTApu8nDjK07l9T7rdSzAHXgb/vm/t 7ksg== X-Gm-Message-State: AOJu0Yy/hMdeiBl/EuQCQBwdgix45wIO+PG07PJKybSEUkVOlrdYuTXv BMQAe+2LGJ0U5SNeKw6FHY2yRL/RPl6Qu1WlrThxZFWdxdH/PaLZdq3h74bThJrHX9otfzL9Zea dQA/+99f2zQ2FLv4twRyUAPv4Ll9szNeHL39Hl6aZSvfFNfnl+56xTEnIGCzUm6uMTvd7V+yFVb y9xN5Y73NE9PeUlhE0gsgmca8fVyuUhaKBSswAWrzoVkD6/gw= X-Gm-Gg: ASbGncvJh0ii+aSgSpSuwp2ZwCdlsq1NnLkCBUdnBxiQ8lAYmGLSrBWwhEC9IjqreFu 3d5cy8dl4LHJbGVYEqF8UNFvDcGa18//j6P6HVkkpbTA/zNVEwIUMmnCk9RZ45MDxun6bOY63Rh 8Ir7YXiauok1vqATYJD7r5RaK1gR3TDVAZdWgm+om1myuIYuOAuRSX/1QAWOtohdBkztozYC1zm wNOI8PvYPih4XclrijMFxkuPCaq5aZ5KU5dhwVbHlPW25TXiahuQSmNSm2hIy+BQdXnVR2TrNYH PlKJp+xyPnc= X-Received: by 2002:a05:620a:1721:b0:7d3:aad4:6f87 with SMTP id af79cd13be357-7d3bc37ba17mr568289585a.7.1749822084980; Fri, 13 Jun 2025 06:41:24 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFqZxKV2mT6BD/bi39sPGRhzywu281UAzYUirAEIW40JfRfajmXwptkVPgbiPNtRrb6I7XH6g== X-Received: by 2002:a05:620a:1721:b0:7d3:aad4:6f87 with SMTP id af79cd13be357-7d3bc37ba17mr568285785a.7.1749822084512; Fri, 13 Jun 2025 06:41:24 -0700 (PDT) Received: from x1.com ([85.131.185.92]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7d3b8ee3f72sm171519285a.94.2025.06.13.06.41.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jun 2025 06:41:23 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org Cc: Andrew Morton , Alex Williamson , Zi Yan , Jason Gunthorpe , Alex Mastro , David Hildenbrand , Nico Pache , peterx@redhat.com Subject: [PATCH 5/5] vfio-pci: Best-effort huge pfnmaps with !MAP_FIXED mappings Date: Fri, 13 Jun 2025 09:41:11 -0400 Message-ID: <20250613134111.469884-6-peterx@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250613134111.469884-1-peterx@redhat.com> References: <20250613134111.469884-1-peterx@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This patch enables best-effort mmap() for vfio-pci bars even without MAP_FIXED, so as to utilize huge pfnmaps as much as possible. It should also avoid userspace changes (switching to MAP_FIXED with pre-aligned VA addresses) to start enabling huge pfnmaps on VFIO bars. Here the trick is making sure the MMIO PFNs will be aligned with the VAs allocated from mmap() when !MAP_FIXED, so that whatever returned from mmap(!MAP_FIXED) of vfio-pci MMIO regions will be automatically suitable for huge pfnmaps as much as possible. To achieve that, a custom vfio_device's get_unmapped_area() for vfio-pci devices is needed. Note that MMIO physical addresses should normally be guaranteed to be always bar-size aligned, hence the bar offset can logically be directly used to do the calculation. However to make it strict and clear (rather than relying on spec details), we still try to fetch the bar's physical addresses from pci_dev.resource[]. Signed-off-by: Alex Williamson Signed-off-by: Peter Xu Reported-by: Alex Mastro --- drivers/vfio/pci/vfio_pci.c | 3 ++ drivers/vfio/pci/vfio_pci_core.c | 65 ++++++++++++++++++++++++++++++++ include/linux/vfio_pci_core.h | 6 +++ 3 files changed, 74 insertions(+) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 5ba39f7623bb..d9ae6cdbea28 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -144,6 +144,9 @@ static const struct vfio_device_ops vfio_pci_ops =3D { .detach_ioas =3D vfio_iommufd_physical_detach_ioas, .pasid_attach_ioas =3D vfio_iommufd_physical_pasid_attach_ioas, .pasid_detach_ioas =3D vfio_iommufd_physical_pasid_detach_ioas, +#ifdef CONFIG_ARCH_SUPPORTS_HUGE_PFNMAP + .get_unmapped_area =3D vfio_pci_core_get_unmapped_area, +#endif }; =20 static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id= *id) diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_c= ore.c index 6328c3a05bcd..835bc168f8b7 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -1641,6 +1641,71 @@ static unsigned long vma_to_pfn(struct vm_area_struc= t *vma) return (pci_resource_start(vdev->pdev, index) >> PAGE_SHIFT) + pgoff; } =20 +#ifdef CONFIG_ARCH_SUPPORTS_HUGE_PFNMAP +/* + * Hint function to provide mmap() virtual address candidate so as to be + * able to map huge pfnmaps as much as possible. It is done by aligning + * the VA to the PFN to be mapped in the specific bar. + * + * Note that this function does the minimum check on mmap() parameters to + * make the PFN calculation valid only. The majority of mmap() sanity check + * will be done later in mmap(). + */ +unsigned long vfio_pci_core_get_unmapped_area(struct vfio_device *device, + struct file *file, + unsigned long addr, + unsigned long len, + unsigned long pgoff, + unsigned long flags) +{ + struct vfio_pci_core_device *vdev =3D + container_of(device, struct vfio_pci_core_device, vdev); + struct pci_dev *pdev =3D vdev->pdev; + unsigned long ret, phys_len, req_start, phys_addr; + unsigned int index; + + index =3D pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT); + + /* Currently, only bars 0-5 supports huge pfnmap */ + if (index >=3D VFIO_PCI_ROM_REGION_INDEX) + goto fallback; + + /* Bar offset */ + req_start =3D (pgoff << PAGE_SHIFT) & ((1UL << VFIO_PCI_OFFSET_SHIFT) - 1= ); + phys_len =3D PAGE_ALIGN(pci_resource_len(pdev, index)); + + /* + * Make sure we at least can get a valid physical address to do the + * math. If this happens, it will probably fail mmap() later.. + */ + if (req_start >=3D phys_len) + goto fallback; + + phys_len =3D MIN(phys_len, len); + /* Calculate the start of physical address to be mapped */ + phys_addr =3D pci_resource_start(pdev, index) + req_start; + + /* Choose the alignment */ + if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP) && phys_len >=3D PUD_SIZE= ) { + ret =3D mm_get_unmapped_area_aligned(file, addr, len, phys_addr, + flags, PUD_SIZE, 0); + if (ret) + return ret; + } + + if (phys_len >=3D PMD_SIZE) { + ret =3D mm_get_unmapped_area_aligned(file, addr, len, phys_addr, + flags, PMD_SIZE, 0); + if (ret) + return ret; + } + +fallback: + return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); +} +EXPORT_SYMBOL_GPL(vfio_pci_core_get_unmapped_area); +#endif + static vm_fault_t vfio_pci_mmap_huge_fault(struct vm_fault *vmf, unsigned int order) { diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index fbb472dd99b3..e59699e01901 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -119,6 +119,12 @@ ssize_t vfio_pci_core_read(struct vfio_device *core_vd= ev, char __user *buf, size_t count, loff_t *ppos); ssize_t vfio_pci_core_write(struct vfio_device *core_vdev, const char __us= er *buf, size_t count, loff_t *ppos); +unsigned long vfio_pci_core_get_unmapped_area(struct vfio_device *device, + struct file *file, + unsigned long addr, + unsigned long len, + unsigned long pgoff, + unsigned long flags); int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struc= t *vma); void vfio_pci_core_request(struct vfio_device *core_vdev, unsigned int cou= nt); int vfio_pci_core_match(struct vfio_device *core_vdev, char *buf); --=20 2.49.0