Re: [PATCH v2] xen-pciback: optionally allow interrupt enable flag writes

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
	xen-devel@lists.xenproject.org
Cc: "Roger Pau Monné" <roger.pau@citrix.com>,
	"Simon Gaiser" <simon@invisiblethingslab.com>,
	"Juergen Gross" <jgross@suse.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	YueHaibing <yuehaibing@huawei.com>,
	"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] xen-pciback: optionally allow interrupt enable flag writes
Date: Fri, 20 Dec 2019 14:11:03 -0500	[thread overview]
Message-ID: <4ed998e1-c8e6-a2c3-031a-9104c912cb76@oracle.com> (raw)
In-Reply-To: <20191219034941.19141-1-marmarek@invisiblethingslab.com>

On 12/18/19 10:49 PM, Marek Marczykowski-Górecki wrote:
> ---
>   drivers/xen/xen-pciback/conf_space.c          | 35 ++++++++
>   drivers/xen/xen-pciback/conf_space.h          | 10 +++
>   .../xen/xen-pciback/conf_space_capability.c   | 88 +++++++++++++++++++
>   drivers/xen/xen-pciback/conf_space_header.c   | 19 ++++
>   drivers/xen/xen-pciback/pci_stub.c            | 66 ++++++++++++++
>   drivers/xen/xen-pciback/pciback.h             |  1 +
>   6 files changed, 219 insertions(+)

This also needs an update to Documentation/ABI/testing/sysfs-driver-pciback.

> @@ -64,6 +64,7 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
>   	int err;
>   	u16 val;
>   	struct pci_cmd_info *cmd = data;
> +	u16 cap_value;

What is this for?

>   
>   	dev_data = pci_get_drvdata(dev);
>   	if (!pci_is_enabled(dev) && is_enable_cmd(value)) {
> @@ -117,6 +118,24 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
>   		pci_clear_mwi(dev);
>   	}
>   
> +	if (dev_data && dev_data->allow_interrupt_control) {
> +		if (!(cmd->val & PCI_COMMAND_INTX_DISABLE) &&
> +		    (value & PCI_COMMAND_INTX_DISABLE)) {
> +			pci_intx(dev, 0);
> +		} else if ((cmd->val & PCI_COMMAND_INTX_DISABLE) &&
> +		    !(value & PCI_COMMAND_INTX_DISABLE)) {
> +			/* Do not allow enabling INTx together with MSI or MSI-X. */
> +			switch (xen_pcibk_get_interrupt_type(dev)) {
> +				case INTERRUPT_TYPE_NONE:
> +				case INTERRUPT_TYPE_INTX:
> +					pci_intx(dev, 1);
> +					break;
> +				default:
> +					return PCIBIOS_SET_FAILED;
> +			}
> +		}

Perhaps this is slightly easier to read:

if (cmd->val ^ val)  &  PCI_COMMAND_INTX_DISABLE) {
         if (value & PCI_COMMAND_INTX_DISABLE) {
                 pci_intx(dev, 0);
         } else {
                 /* Do not allow enabling INTx together with MSI or 
MSI-X. */
             switch (xen_pcibk_get_interrupt_type(dev)) {
                 case INTERRUPT_TYPE_NONE:
                 case INTERRUPT_TYPE_INTX:
                     pci_intx(dev, 1);
                     break;
                 default:
                     return PCIBIOS_SET_FAILED;
             }
        }
}

And also, if INTERRUPT_TYPE_INTX, aren't you already enabled?

-boris