[SLOF] [PATCH v2 12/19] virtio: add 64-bit virtio helpers for 1.0

Thomas Huth thuth at redhat.com
Fri Jan 22 17:30:15 AEDT 2016


On 22.01.2016 06:25, Alexey Kardashevskiy wrote:
> On 01/22/2016 04:18 PM, Nikunj A Dadhania wrote:
>> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
>>
>>> On 01/21/2016 06:58 PM, Nikunj A Dadhania wrote:
>>>> Thomas Huth <thuth at redhat.com> writes:
>>>>
>>>>> On 20.01.2016 13:10, Nikunj A Dadhania wrote:
>>>>>>    } __attribute__ ((packed));
>>>>>>
>>>>>> +/* virtio 1.0 Spec: 4.1.3 PCI Device Layout
>>>>>> + *
>>>>>> + * Fields of different sizes are present in the device
>>>>>> configuration regions.
>>>>>> + * All 64-bit, 32-bit and 16-bit fields are little-endian. 64-bit
>>>>>> fields are to
>>>>>> + * be treated as two 32-bit fields, with low 32 bit part followed
>>>>>> by the high 32
>>>>>> + * bit part.
>>>>>> + */
>>>>>> +static void virtio_write64(void *addr, uint64_t val)
>>>>>> +{
>>>>>> +    uint32_t hi = (val >> 32) & 0xFFFFFFFF;
>>>>>> +    uint32_t lo = val & 0xFFFFFFFF;
>>>>>> +
>>>>>> +    ci_write_32(addr, cpu_to_le32(lo));
>>>>>> +    ci_write_32(addr + 4, cpu_to_le32(hi));
>>>>>> +}
>>>>>> +
>>>>>> +static uint64_t virtio_read64(void *addr)
>>>>>> +{
>>>>>> +    uint64_t hi, lo;
>>>>>> +
>>>>>> +    lo = le32_to_cpu(ci_read_32(addr));
>>>>>> +    hi = le32_to_cpu(ci_read_32(addr + 4));
>>>>>> +    return (hi << 32) | lo;
>>>>>> +}
>>>>>
>>>>> I'd maybe name them "virtio_pci_write64" and "virtio_pci_read64" to
>>>>> make
>>>>> it clear that they are only to be used when reading and writing to the
>>>>> PCI space - otherwise somebody might use them for accessing the virtio
>>>>> rings one day, for example.
>>>>
>>>> Right, will rename.
>>>
>>>
>>> I'd rename these to virtio_ci_write_64/virtio_ci_read_64 as they are
>>> wrappers on top of ci_read_xx/ci_write_xx. And frankly they can be
>>> used to
>>> access any guest physical memory and any MMIO.
>>
>> They can be used, but should not be, as the register in MMIO are not
>> split into two registers (hi,low).This is  very specific to VIRTIO PCI.
>> IMO, the current naming is correct.
> 
> 
> This is why I kept "virtio_" prefix. PCI is redundant here - there is no
> other virtio, and "ci" is what it really does. Thomas?

The split for 2x 32-bit only makes sense for the PCI access, so I'd also
use "_pci_" here.

 Thomas



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