Re: [PATCH v5 09/14] vpci/header: emulate PCI_COMMAND register for guests

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Nov 25, 2021 at 01:02:46PM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> 
> Add basic emulation support for guests. At the moment only emulate
> PCI_COMMAND_INTX_DISABLE bit, the rest is not emulated yet and left
> as TODO.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> ---
> Since v3:
> - gate more code on CONFIG_HAS_MSI
> - removed logic for the case when MSI/MSI-X not enabled
> ---
>  xen/drivers/vpci/header.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index b0499d32c5d8..2e44055946b0 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -491,6 +491,22 @@ static void cmd_write(const struct pci_dev *pdev, 
> unsigned int reg,
>          pci_conf_write16(pdev->sbdf, reg, cmd);
>  }
>  
> +static void guest_cmd_write(const struct pci_dev *pdev, unsigned int reg,
> +                            uint32_t cmd, void *data)
> +{
> +    /* TODO: Add proper emulation for all bits of the command register. */
> +
> +#ifdef CONFIG_HAS_PCI_MSI
> +    if ( pdev->vpci->msi->enabled )

You need to check for MSI-X also, pdev->vpci->msix->enabled.

> +    {
> +        /* Guest wants to enable INTx. It can't be enabled if MSI/MSI-X 
> enabled. */
> +        cmd |= PCI_COMMAND_INTX_DISABLE;

You will also need to make sure PCI_COMMAND_INTX_DISABLE is set in the
command register when attempting to enable MSI or MSIX capabilities.

Thanks, Roger.