linux-kernel - Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt types use same signature

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Date: Mon, 5 Feb 2024 15:35:42 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: jgg@...dia.com, yishaih@...dia.com,
 shameerali.kolothum.thodi@...wei.com, kevin.tian@...el.com,
 kvm@...r.kernel.org, dave.jiang@...el.com, ashok.raj@...el.com,
 linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt
 types use same signature

On Thu,  1 Feb 2024 20:57:09 -0800
Reinette Chatre <reinette.chatre@...el.com> wrote:

> vfio_pci_set_intx_trigger() and vfio_pci_set_msi_trigger() have
> flows that can be shared.
> 
> For INTx, MSI, and MSI-X interrupt management to share the
> same enable/disable flow the interrupt specific enable and
> disable functions should have the same signatures.
> 
> Let vfio_intx_enable() and vfio_msi_enable() use the same
> parameters by passing "start" and "count" to these functions
> instead of letting the (what will eventually be) common code
> interpret these values.
> 
> Providing "start" and "count" to vfio_intx_enable()
> enables the INTx specific check of these parameters to move into
> the INTx specific vfio_intx_enable(). Similarly, providing "start"
> and "count" to vfio_msi_enable() enables the MSI/MSI-X specific
> code to initialize number of vectors needed.
> 
> The shared MSI/MSI-X code needs the interrupt index. Provide
> the interrupt index (clearly marked as unused) to the INTx code
> to use the same signatures.
> 
> With interrupt type specific code using the same parameters it
> is possible to have common code that calls the enable/disable
> code for different interrupt types.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 37065623d286..9217fea3f636 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -257,13 +257,18 @@ static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
>  	return ret;
>  }
>  
> -static int vfio_intx_enable(struct vfio_pci_core_device *vdev)
> +static int vfio_intx_enable(struct vfio_pci_core_device *vdev,
> +			    unsigned int start, unsigned int count,
> +			    unsigned int __always_unused index)
>  {
>  	struct vfio_pci_irq_ctx *ctx;
>  
>  	if (!is_irq_none(vdev))
>  		return -EINVAL;
>  
> +	if (start != 0 || count != 1)
> +		return -EINVAL;
> +
>  	if (!vdev->pdev->irq)
>  		return -ENODEV;
>  
> @@ -332,7 +337,8 @@ static char *vfio_intx_device_name(struct vfio_pci_core_device *vdev,
>  	return kasprintf(GFP_KERNEL_ACCOUNT, "vfio-intx(%s)", pci_name(pdev));
>  }
>  
> -static void vfio_intx_disable(struct vfio_pci_core_device *vdev)
> +static void vfio_intx_disable(struct vfio_pci_core_device *vdev,
> +			      unsigned int __always_unused index)
>  {
>  	struct vfio_pci_irq_ctx *ctx;
>  
> @@ -358,17 +364,20 @@ static irqreturn_t vfio_msihandler(int irq, void *arg)
>  	return IRQ_HANDLED;
>  }
>  
> -static int vfio_msi_enable(struct vfio_pci_core_device *vdev, int nvec,
> +static int vfio_msi_enable(struct vfio_pci_core_device *vdev,
> +			   unsigned int start, unsigned int count,
>  			   unsigned int index)
>  {
>  	struct pci_dev *pdev = vdev->pdev;
>  	unsigned int flag;
> -	int ret;
> +	int ret, nvec;
>  	u16 cmd;
>  
>  	if (!is_irq_none(vdev))
>  		return -EINVAL;
>  
> +	nvec = start + count;
> +
>  	flag = (index == VFIO_PCI_MSIX_IRQ_INDEX) ? PCI_IRQ_MSIX : PCI_IRQ_MSI;
>  
>  	/* return the number of supported vectors if we can't get all: */
> @@ -701,11 +710,11 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
>  	unsigned int i;
>  
>  	if (is_intx(vdev) && !count && (flags & VFIO_IRQ_SET_DATA_NONE)) {
> -		vfio_intx_disable(vdev);
> +		vfio_intx_disable(vdev, index);
>  		return 0;
>  	}
>  
> -	if (!(is_intx(vdev) || is_irq_none(vdev)) || start != 0 || count != 1)
> +	if (!(is_intx(vdev) || is_irq_none(vdev)))
>  		return -EINVAL;
>  
>  	if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
> @@ -715,13 +724,13 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
>  		if (is_intx(vdev))
>  			return vfio_irq_set_block(vdev, start, count, fds, index);
>  
> -		ret = vfio_intx_enable(vdev);
> +		ret = vfio_intx_enable(vdev, start, count, index);

Please trace what happens when a user calls SET_IRQS to setup a trigger
eventfd with start = 0, count = 1, followed by any other combination of
start and count values once is_intx() is true.  vfio_intx_enable()
cannot be the only place we bounds check the user, all of the INTx
callbacks should be an error or nop if vector != 0.  Thanks,

Alex

>  		if (ret)
>  			return ret;
>  
>  		ret = vfio_irq_set_block(vdev, start, count, fds, index);
>  		if (ret)
> -			vfio_intx_disable(vdev);
> +			vfio_intx_disable(vdev, index);
>  
>  		return ret;
>  	}
> @@ -771,7 +780,7 @@ static int vfio_pci_set_msi_trigger(struct vfio_pci_core_device *vdev,
>  			return vfio_irq_set_block(vdev, start, count,
>  						  fds, index);
>  
> -		ret = vfio_msi_enable(vdev, start + count, index);
> +		ret = vfio_msi_enable(vdev, start, count, index);
>  		if (ret)
>  			return ret;
>