Re: [PATCH V7 07/11] vpci/header: emulate PCI_COMMAND register for guests

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.07.2022 19:42, Oleksandr Tyshchenko wrote:
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -443,11 +443,27 @@ static int modify_bars(const struct pci_dev *pdev, 
> uint16_t cmd, bool rom_only)
>      return 0;
>  }
>  
> +/* TODO: Add proper emulation for all bits of the command register. */
>  static void cf_check cmd_write(
>      const struct pci_dev *pdev, unsigned int reg, uint32_t cmd, void *data)
>  {
>      uint16_t current_cmd = pci_conf_read16(pdev->sbdf, reg);
>  
> +    if ( !is_hardware_domain(pdev->domain) )
> +    {
> +        struct vpci_header *header = data;
> +
> +        header->guest_cmd = cmd;
> +#ifdef CONFIG_HAS_PCI_MSI
> +        if ( pdev->vpci->msi->enabled || pdev->vpci->msix->enabled )
> +            /*
> +             * Guest wants to enable INTx, but it can't be enabled
> +             * if MSI/MSI-X enabled.
> +             */
> +            cmd |= PCI_COMMAND_INTX_DISABLE;
> +#endif
> +    }
> +
>      /*
>       * Let Dom0 play with all the bits directly except for the memory
>       * decoding one.
> @@ -464,6 +480,19 @@ static void cf_check cmd_write(
>          pci_conf_write16(pdev->sbdf, reg, cmd);
>  }
>  
> +static uint32_t cf_check cmd_read(
> +    const struct pci_dev *pdev, unsigned int reg, void *data)
> +{
> +    if ( !is_hardware_domain(pdev->domain) )
> +    {
> +        struct vpci_header *header = data;
> +
> +        return header->guest_cmd;
> +    }
> +
> +    return pci_conf_read16(pdev->sbdf, reg);
> +}

This function wants the same leading comment as cmd_write(). I also
think you better wouldn't give the guest the impression that r/o bits
can actually be written to (but getting this right may well fall
under the TODO).

Jan