Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 13 Dec 2018 09:13:20 +0000
From:   "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     Vivek Goyal <vgoyal@redhat.com>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        miklos@szeredi.hu, stefanha@redhat.com, sweil@redhat.com,
        swhiteho@redhat.com
Subject: Re: [PATCH 18/52] virtio-fs: Map cache using the values from the
 capabilities
Message-ID: <20181213091320.GA2313@work-vm>
References: <20181210171318.16998-1-vgoyal@redhat.com>
 <20181210171318.16998-19-vgoyal@redhat.com>
 <de46a955-813b-355d-49f2-4d866603a8fa@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <de46a955-813b-355d-49f2-4d866603a8fa@redhat.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

* David Hildenbrand (david@redhat.com) wrote:
> On 10.12.18 18:12, Vivek Goyal wrote:
> > Instead of assuming we had the fixed bar for the cache, use the
> > value from the capabilities.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  fs/fuse/virtio_fs.c | 32 +++++++++++++++++---------------
> >  1 file changed, 17 insertions(+), 15 deletions(-)
> > 
> > diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> > index 60d496c16841..55bac1465536 100644
> > --- a/fs/fuse/virtio_fs.c
> > +++ b/fs/fuse/virtio_fs.c
> > @@ -14,11 +14,6 @@
> >  #include <uapi/linux/virtio_pci.h>
> >  #include "fuse_i.h"
> >  
> > -enum {
> > -	/* PCI BAR number of the virtio-fs DAX window */
> > -	VIRTIO_FS_WINDOW_BAR = 2,
> > -};
> > -
> >  /* List of virtio-fs device instances and a lock for the list */
> >  static DEFINE_MUTEX(virtio_fs_mutex);
> >  static LIST_HEAD(virtio_fs_instances);
> > @@ -518,7 +513,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> >  	struct dev_pagemap *pgmap;
> >  	struct pci_dev *pci_dev;
> >  	phys_addr_t phys_addr;
> > -	size_t len;
> > +	size_t bar_len;
> >  	int ret;
> >  	u8 have_cache, cache_bar;
> >  	u64 cache_offset, cache_len;
> > @@ -551,17 +546,13 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> >          }
> >  
> >  	/* TODO handle case where device doesn't expose BAR? */
> 
> For virtio-pmem we decided to not go via BARs as this would effectively
> make it only usable for virtio-pci implementers. Instead, we are going
> to export the applicable physical device region directly (e.g.
> phys_start, phys_size in virtio config), so it is decoupled from PCI
> details. Doing the same for virtio-fs would allow e.g. also virtio-ccw
> to make eventually use of this.

That makes it a very odd looking PCI device;  I can see that with
virtio-pmem it makes some sense, given that it's job is to expose
arbitrary chunks of memory.

Dave


> > -	ret = pci_request_region(pci_dev, VIRTIO_FS_WINDOW_BAR,
> > -				 "virtio-fs-window");
> > +	ret = pci_request_region(pci_dev, cache_bar, "virtio-fs-window");
> >  	if (ret < 0) {
> >  		dev_err(&vdev->dev, "%s: failed to request window BAR\n",
> >  			__func__);
> >  		return ret;
> >  	}
> >  
> > -	phys_addr = pci_resource_start(pci_dev, VIRTIO_FS_WINDOW_BAR);
> > -	len = pci_resource_len(pci_dev, VIRTIO_FS_WINDOW_BAR);
> > -
> >  	mi = devm_kzalloc(&pci_dev->dev, sizeof(*mi), GFP_KERNEL);
> >  	if (!mi)
> >  		return -ENOMEM;
> > @@ -586,6 +577,17 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> >  	pgmap->ref = &mi->ref;
> >  	pgmap->type = MEMORY_DEVICE_FS_DAX;
> >  
> > +	phys_addr = pci_resource_start(pci_dev, cache_bar);
> > +	bar_len = pci_resource_len(pci_dev, cache_bar);
> > +
> > +	if (cache_offset + cache_len > bar_len) {
> > +		dev_err(&vdev->dev,
> > +			"%s: cache bar shorter than cap offset+len\n",
> > +			__func__);
> > +		return -EINVAL;
> > +	}
> > +	phys_addr += cache_offset;
> > +
> >  	/* Ideally we would directly use the PCI BAR resource but
> >  	 * devm_memremap_pages() wants its own copy in pgmap.  So
> >  	 * initialize a struct resource from scratch (only the start
> > @@ -594,7 +596,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> >  	pgmap->res = (struct resource){
> >  		.name = "virtio-fs dax window",
> >  		.start = phys_addr,
> > -		.end = phys_addr + len,
> > +		.end = phys_addr + cache_len,
> >  	};
> >  
> >  	fs->window_kaddr = devm_memremap_pages(&pci_dev->dev, pgmap);
> > @@ -607,10 +609,10 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> >  		return ret;
> >  
> >  	fs->window_phys_addr = phys_addr;
> > -	fs->window_len = len;
> > +	fs->window_len = cache_len;
> >  
> > -	dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len %zu\n",
> > -		__func__, fs->window_kaddr, phys_addr, len);
> > +	dev_dbg(&vdev->dev, "%s: cache kaddr 0x%px phys_addr 0x%llx len %llx\n",
> > +		__func__, fs->window_kaddr, phys_addr, cache_len);
> >  
> >  	fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops);
> >  	if (!fs->dax_dev)
> > 
> 
> 
> -- 
> 
> Thanks,
> 
> David / dhildenb
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK