Hi, Roger!
On 26.10.21 13:52, Roger Pau Monné wrote:
> On Thu, Sep 30, 2021 at 10:52:20AM +0300, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
>>
>> 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_andrushche...@epam.com>
>> Reviewed-by: Michal Orzel <michal.or...@arm.com>
>> ---
>> New in v2
>> ---
>> xen/drivers/vpci/header.c | 35 ++++++++++++++++++++++++++++++++---
>> 1 file changed, 32 insertions(+), 3 deletions(-)
>>
>> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
>> index f23c956cde6c..754aeb5a584f 100644
>> --- a/xen/drivers/vpci/header.c
>> +++ b/xen/drivers/vpci/header.c
>> @@ -451,6 +451,32 @@ 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. */
>> +
>> + if ( (cmd & PCI_COMMAND_INTX_DISABLE) == 0 )
>> + {
>> + /*
>> + * Guest wants to enable INTx. It can't be enabled if:
>> + * - host has INTx disabled
>> + * - MSI/MSI-X enabled
>> + */
>> + if ( pdev->vpci->msi->enabled )
>> + cmd |= PCI_COMMAND_INTX_DISABLE;
>> + else
>> + {
>> + uint16_t current_cmd = pci_conf_read16(pdev->sbdf, reg);
>> +
>> + if ( current_cmd & PCI_COMMAND_INTX_DISABLE )
>> + cmd |= PCI_COMMAND_INTX_DISABLE;
>> + }
> This last part should be Arm specific. On other architectures we
> likely want the guest to modify INTx disable in order to select the
> interrupt delivery mode for the device.
This is not arch specific as we just do not allow INTx to be enabled
if MSI/MSI-X has been enabled before. This was discussed previously
(Jan) and this was pointed as an acceptable approach to limit the
guest from having inconsistent configuration
>
> I really wonder if we should allow the guest to play with any other
> bit apart from INTx disable and memory and IO decoding on the command
> register.
This needs to be implemented one day when we understand what
this emulation should look like. This is why I have a "TODO" above.
>
> Thanks, Roger.
Thank you,
Oleksandr
