Re: [PATCH v3 10/11] vpci/msi: Free MSI resources when init_msi() fails

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

On Mon, Apr 21, 2025 at 02:19:02PM +0800, Jiqian Chen wrote:
> When init_msi() fails, the previous new changes will hide MSI
> capability, it can't rely on vpci_deassign_device() to remove
> all MSI related resources anymore, those resources must be
> cleaned up in failure path of init_msi.
> 
> To do that, add a new function to free MSI resources.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> ---
> cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
> ---
> v2->v3 changes:
> * Remove all fail path, and use fini_msi() hook instead.
> * Change the method to calculating the size of msi registers.
> 
> v1->v2 changes:
> * Added a new function fini_msi to free all MSI resources instead of using an 
> array to record registered registers.
> 
> Best regards,
> Jiqian Chen.
> ---
>  xen/drivers/vpci/msi.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/drivers/vpci/msi.c b/xen/drivers/vpci/msi.c
> index ea7dc0c060ea..18b06b789827 100644
> --- a/xen/drivers/vpci/msi.c
> +++ b/xen/drivers/vpci/msi.c
> @@ -193,6 +193,32 @@ static void cf_check mask_write(
>      msi->mask = val;
>  }
>  
> +static void fini_msi(struct pci_dev *pdev)
> +{
> +    unsigned int end, size;
> +    struct vpci *vpci = pdev->vpci;
> +    const unsigned int msi_pos = pdev->msi_pos;
> +
> +    if ( !msi_pos || !vpci->msi )
> +        return;
> +
> +    if ( vpci->msi->masking )
> +        end = msi_pending_bits_reg(msi_pos, vpci->msi->address64);
> +    else
> +        end = msi_mask_bits_reg(msi_pos, vpci->msi->address64) - 2;
> +
> +    size = end - msi_control_reg(msi_pos);
> +
> +    /*
> +     * Remove all possible registered registers except capability ID
> +     * register if guest and next capability pointer register, which
> +     * will be removed in mask function.

The above text seems very convoluted.  I prefer re-using the same
comment that you had in the ReBAR cleanup helper:

    /*
     * Remove all possible registered registers except header.
     * Header register will be removed in mask function.
     */

> +     */
> +    vpci_remove_registers(vpci, msi_control_reg(msi_pos), size);
> +    xfree(vpci->msi);
> +    vpci->msi = NULL;

XFREE(vpci->msi);

Will be more compact.

Thanks, Roger.