Re: [PATCH v4 05/11] vpci/header: implement guest BAR register handlers

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.11.2021 13:54, Oleksandr Andrushchenko wrote:
> On 19.11.21 14:49, Jan Beulich wrote:
>> On 19.11.2021 13:46, Oleksandr Andrushchenko wrote:
>>> On 19.11.21 14:37, Jan Beulich wrote:
>>>> On 19.11.2021 13:10, Oleksandr Andrushchenko wrote:
>>>>> On 19.11.21 13:58, Jan Beulich wrote:
>>>>>> On 05.11.2021 07:56, Oleksandr Andrushchenko wrote:
>>>>>>> --- a/xen/drivers/vpci/header.c
>>>>>>> +++ b/xen/drivers/vpci/header.c
>>>>>>> @@ -408,6 +408,48 @@ static void bar_write(const struct pci_dev *pdev, 
>>>>>>> unsigned int reg,
>>>>>>>         pci_conf_write32(pdev->sbdf, reg, val);
>>>>>>>     }
>>>>>>>     
>>>>>>> +static void guest_bar_write(const struct pci_dev *pdev, unsigned int 
>>>>>>> reg,
>>>>>>> +                            uint32_t val, void *data)
>>>>>>> +{
>>>>>>> +    struct vpci_bar *bar = data;
>>>>>>> +    bool hi = false;
>>>>>>> +
>>>>>>> +    if ( bar->type == VPCI_BAR_MEM64_HI )
>>>>>>> +    {
>>>>>>> +        ASSERT(reg > PCI_BASE_ADDRESS_0);
>>>>>>> +        bar--;
>>>>>>> +        hi = true;
>>>>>>> +    }
>>>>>>> +    else
>>>>>>> +    {
>>>>>>> +        val &= PCI_BASE_ADDRESS_MEM_MASK;
>>>>>>> +        val |= bar->type == VPCI_BAR_MEM32 ? 
>>>>>>> PCI_BASE_ADDRESS_MEM_TYPE_32
>>>>>>> +                                           : 
>>>>>>> PCI_BASE_ADDRESS_MEM_TYPE_64;
>>>>>>> +        val |= bar->prefetchable ? PCI_BASE_ADDRESS_MEM_PREFETCH : 0;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    bar->guest_addr &= ~(0xffffffffull << (hi ? 32 : 0));
>>>>>>> +    bar->guest_addr |= (uint64_t)val << (hi ? 32 : 0);
>>>>>>> +
>>>>>>> +    bar->guest_addr &= ~(bar->size - 1) | ~PCI_BASE_ADDRESS_MEM_MASK;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static uint32_t guest_bar_read(const struct pci_dev *pdev, unsigned 
>>>>>>> int reg,
>>>>>>> +                               void *data)
>>>>>>> +{
>>>>>>> +    const struct vpci_bar *bar = data;
>>>>>>> +    bool hi = false;
>>>>>>> +
>>>>>>> +    if ( bar->type == VPCI_BAR_MEM64_HI )
>>>>>>> +    {
>>>>>>> +        ASSERT(reg > PCI_BASE_ADDRESS_0);
>>>>>>> +        bar--;
>>>>>>> +        hi = true;
>>>>>>> +    }
>>>>>>> +
>>>>>>> +    return bar->guest_addr >> (hi ? 32 : 0);
>>>>>> I'm afraid "guest_addr" then isn't the best name; maybe "guest_val"?
>>>>>> This would make more obvious that there is a meaningful difference
>>>>>> from "addr" besides the guest vs host aspect.
>>>>> I am not sure I can agree here:
>>>>> bar->addr and bar->guest_addr make it clear what are these while
>>>>> bar->addr and bar->guest_val would make someone go look for
>>>>> additional information about what that val is for.
>>>> Feel free to replace "val" with something more suitable. "guest_bar"
>>>> maybe? The value definitely is not an address, so "addr" seems
>>>> inappropriate / misleading to me.
>>> This is a guest's view on the BAR's address. So to me it is still guest_addr
>> It's a guest's view on the BAR, not just the address. Or else you couldn't
>> simply return the value here without folding in the correct low bits.
> I agree with this this respect as it is indeed address + lower bits.
> How about guest_bar_val then? So it reflects its nature, e.g. the value
> of the BAR as seen by the guest.

Gets a little longish for my taste. I for one wouldn't mind it be just
"guest". In the end Roger has the final say here anyway.

Jan