Re: [PATCH v3 08/11] vpci/header: Emulate PCI_COMMAND register for guests

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 03.11.21 13:26, Roger Pau Monné wrote:
> On Wed, Nov 03, 2021 at 11:02:37AM +0000, Oleksandr Andrushchenko wrote:
>>
>> On 03.11.21 13:01, Roger Pau Monné wrote:
>>> On Wed, Nov 03, 2021 at 10:36:36AM +0000, Oleksandr Andrushchenko wrote:
>>>> On 03.11.21 12:34, Jan Beulich wrote:
>>>>> On 03.11.2021 11:24, Oleksandr Andrushchenko wrote:
>>>>>> On 03.11.21 11:49, Jan Beulich wrote:
>>>>>>> Aiui you want to prevent the guest from clearing the bit if either
>>>>>>> MSI or MSI-X are in use. Symmetrically, when the guest enables MSI
>>>>>>> or MSI-X, you will want to force the bit set (which may well be in
>>>>>>> a separate, future patch).
>>>>>> static uint32_t emulate_cmd_reg(const struct pci_dev *pdev, uint32_t cmd)
>>>>>> {
>>>>>>         /* TODO: Add proper emulation for all bits of the command 
>>>>>> register. */
>>>>>>
>>>>>>         if ( (cmd & PCI_COMMAND_INTX_DISABLE) == 0 )
>>>>>>         {
>>>>>>             /* Guest wants to enable INTx. It can't be enabled if 
>>>>>> MSI/MSI-X enabled. */
>>>>>> #ifdef CONFIG_HAS_PCI_MSI
>>>>>>             if ( pdev->vpci->msi->enabled )
>>>>>>                 cmd |= PCI_COMMAND_INTX_DISABLE;
>>>>>> #endif
>>>>>>         }
>>>>>>
>>>>>>         return cmd;
>>>>>> }
>>>>>>
>>>>>> Is this what you mean?
>>>>> Something along these lines, yes. I'd omit the outer if() for clarity /
>>>>> brevity.
>>>> Sure, thank you!
>>>> @Roger are you ok with this approach?
>>> Sure, I would even do:
>>>
>>> #ifdef CONFIG_HAS_PCI_MSI
>>> if ( !(cmd & PCI_COMMAND_INTX_DISABLE) && pdev->vpci->msi->enabled )
>>> {
>>>       /* Guest wants to enable INTx. It can't be enabled if MSI/MSI-X 
>>> enabled. */
>>>       cmd |= PCI_COMMAND_INTX_DISABLE;
>>> }
>>> #endif
>>>
>>> There's no need for the outer check if there's no support for MSI.
>> Ok, sounds good!
>> Thank you both!!
> In fact you could even remove the check for !(cmd &
> PCI_COMMAND_INTX_DISABLE) and always set PCI_COMMAND_INTX_DISABLE if
> MSI is enabled, which I think is what Jan was pointing to in his
> previous reply.
Ok, I will
>
> Regards, Roger.
>