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Date:	Tue, 16 Jun 2015 16:11:21 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Gerd Hoffmann <kraxel@...hat.com>
Cc:	"open list:VIRTIO CORE, NET..." 
	<virtualization@...ts.linux-foundation.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio-pci: alloc only resources actually used.

On Tue, Jun 16, 2015 at 03:57:52PM +0200, Gerd Hoffmann wrote:
> Move resource allocation from common code to legacy and modern code.
> Only request resources actually used, i.e. bar0 in legacy mode and
> the regions specified by capabilities in modern mode.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/virtio/virtio_pci_common.c |  7 -----
>  drivers/virtio/virtio_pci_common.h |  5 ++++
>  drivers/virtio/virtio_pci_legacy.c | 13 +++++++++-
>  drivers/virtio/virtio_pci_modern.c | 52 +++++++++++++++++++++++++++++++++++++-
>  4 files changed, 68 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index eba1b7a..327a121 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -510,10 +510,6 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
>  	if (rc)
>  		goto err_enable_device;
>  
> -	rc = pci_request_regions(pci_dev, "virtio-pci");
> -	if (rc)
> -		goto err_request_regions;
> -
>  	if (force_legacy) {
>  		rc = virtio_pci_legacy_probe(vp_dev);
>  		/* Also try modern mode if we can't map BAR0 (no IO space). */
> @@ -543,8 +539,6 @@ err_register:
>  	else
>  	     virtio_pci_modern_remove(vp_dev);
>  err_probe:
> -	pci_release_regions(pci_dev);
> -err_request_regions:
>  	pci_disable_device(pci_dev);
>  err_enable_device:
>  	kfree(vp_dev);
> @@ -562,7 +556,6 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
>  	else
>  		virtio_pci_modern_remove(vp_dev);
>  
> -	pci_release_regions(pci_dev);
>  	pci_disable_device(pci_dev);
>  }
>  
> diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> index 28ee4e5..9e744b8 100644
> --- a/drivers/virtio/virtio_pci_common.h
> +++ b/drivers/virtio/virtio_pci_common.h
> @@ -75,6 +75,11 @@ struct virtio_pci_device {
>  	/* Multiply queue_notify_off by this value. (non-legacy mode). */
>  	u32 notify_offset_multiplier;
>  
> +	struct resource *res_common;
> +	struct resource *res_isr;
> +	struct resource *res_device;
> +	struct resource *res_notify;
> +
>  	/* Legacy only field */
>  	/* the IO mapping for the PCI config space */
>  	void __iomem *ioaddr;
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index 256a527..48bc979 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -215,6 +215,7 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
>  int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
>  {
>  	struct pci_dev *pci_dev = vp_dev->pci_dev;
> +	int rc;
>  
>  	/* We only own devices >= 0x1000 and <= 0x103f: leave the rest. */
>  	if (pci_dev->device < 0x1000 || pci_dev->device > 0x103f)
> @@ -226,9 +227,14 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
>  		return -ENODEV;
>  	}
>  
> +	rc = pci_request_region(pci_dev, 0, "virtio-pci-legacy");
> +	if (rc)
> +		return rc;
> +
> +	rc = -ENOMEM;
>  	vp_dev->ioaddr = pci_iomap(pci_dev, 0, 0);
>  	if (!vp_dev->ioaddr)
> -		return -ENOMEM;
> +		goto err_iomap;
>  
>  	vp_dev->isr = vp_dev->ioaddr + VIRTIO_PCI_ISR;
>  
> @@ -246,6 +252,10 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
>  	vp_dev->del_vq = del_vq;
>  
>  	return 0;
> +
> +err_iomap:
> +	pci_release_region(pci_dev, 0);
> +	return rc;
>  }
>  
>  void virtio_pci_legacy_remove(struct virtio_pci_device *vp_dev)
> @@ -253,4 +263,5 @@ void virtio_pci_legacy_remove(struct virtio_pci_device *vp_dev)
>  	struct pci_dev *pci_dev = vp_dev->pci_dev;
>  
>  	pci_iounmap(pci_dev, vp_dev->ioaddr);
> +	pci_release_region(pci_dev, 0);
>  }
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index e88e099..b4bd92b 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -64,6 +64,24 @@ static void vp_iowrite64_twopart(u64 val,
>  	vp_iowrite32(val >> 32, hi);
>  }
>  
> +static struct resource *request_capability(struct pci_dev *dev, int off,
> +					   const char *name)
> +{
> +	u8 bar;
> +	u32 offset, length;
> +
> +	pci_read_config_byte(dev, off + offsetof(struct virtio_pci_cap,
> +						 bar),
> +			     &bar);
> +	pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, offset),
> +			     &offset);
> +	pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, length),
> +			      &length);
> +
> +	return request_mem_region(pci_resource_start(dev, bar) + offset,
> +				  length, name);
> +}
> +

For device config, this might request too much. The spec says:
	The drivers SHOULD only map part of configuration structure large enough
	for device operation.
I think you should limit this to PAGE_SIZE like we do for map_capability.

>  static void __iomem *map_capability(struct pci_dev *dev, int off,
>  				    size_t minlen,
>  				    u32 align,
> @@ -131,10 +149,12 @@ static void __iomem *map_capability(struct pci_dev *dev, int off,
>  	}
>  
>  	p = pci_iomap_range(dev, bar, offset, length);
> -	if (!p)
> +	if (!p) {
>  		dev_err(&dev->dev,
>  			"virtio_pci: unable to map virtio %u@%u on bar %i\n",
>  			length, offset, bar);
> +		return NULL;
> +	}
>  	return p;
>  }
>  
> @@ -642,6 +662,21 @@ int virtio_pci_modern_probe(struct virtio_pci_device *vp_dev)
>  	device = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_DEVICE_CFG,
>  					    IORESOURCE_IO | IORESOURCE_MEM);
>  
> +	vp_dev->res_common = request_capability(pci_dev, common,
> +						"virtio-pci-common");
> +	vp_dev->res_isr = request_capability(pci_dev, isr,
> +						"virtio-pci-isr");
> +	vp_dev->res_notify = request_capability(pci_dev, notify,
> +						"virtio-pci-notify");
> +	if (device) {
> +		vp_dev->res_device = request_capability(pci_dev, device,
> +							"virtio-pci-device");
> +	}
> +	err = -EINVAL;
> +	if (!vp_dev->res_common || !vp_dev->res_isr || !vp_dev->res_notify ||
> +	    (device && !vp_dev->res_device))
> +		goto err_reserve;
> +
>  	err = -EINVAL;
>  	vp_dev->common = map_capability(pci_dev, common,
>  					sizeof(struct virtio_pci_common_cfg), 4,

map_capability has a bunch of checks in place to validate the capability
structure. With request_capability called earlier, they are now done too
late.

> @@ -714,6 +749,15 @@ err_map_notify:
>  err_map_isr:
>  	pci_iounmap(pci_dev, vp_dev->common);
>  err_map_common:
> +err_reserve:
> +	if (vp_dev->res_common)
> +		release_resource(vp_dev->res_common);
> +	if (vp_dev->res_isr)
> +		release_resource(vp_dev->res_isr);
> +	if (vp_dev->res_notify)
> +		release_resource(vp_dev->res_notify);
> +	if (vp_dev->res_device)
> +		release_resource(vp_dev->res_device);
>  	return err;
>  }
>  
> @@ -727,4 +771,10 @@ void virtio_pci_modern_remove(struct virtio_pci_device *vp_dev)
>  		pci_iounmap(pci_dev, vp_dev->notify_base);
>  	pci_iounmap(pci_dev, vp_dev->isr);
>  	pci_iounmap(pci_dev, vp_dev->common);
> +
> +	release_resource(vp_dev->res_common);
> +	release_resource(vp_dev->res_isr);
> +	release_resource(vp_dev->res_notify);
> +	if (vp_dev->res_device)
> +		release_resource(vp_dev->res_device);
>  }
> -- 
> 1.8.3.1
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