Re: [Qemu-ppc] [PATCHv5 07/12] libqos: Implement mmio accessors in terms of mem{read, write}

[Alexey Kardashevskiy]

On 25/10/16 23:16, David Gibson wrote:
> On Tue, Oct 25, 2016 at 05:47:43PM +1100, Alexey Kardashevskiy wrote:
>> On 24/10/16 15:59, David Gibson wrote:
>>> In the libqos PCI code we now have accessors both for registers (byte
>>> significance preserving) and for streaming data (byte address order
>>> preserving).  These exist in both the interface for qtest drivers and in
>>> the machine specific backends.
>>>
>>> However, the register-style accessors aren't actually necessary in the
>>> backend.  They can be implemented in terms of the byte address order
>>> preserving accessors by the libqos wrappers.  This works because PCI is
>>> always little endian.
>>>
>>> This does assume that the back end byte address order preserving accessors
>>> will perform the equivalent of a single bus transaction for short lengths.
>>> This is the case, and in fact they currently end up using the same
>>> cpu_physical_memory_rw() implementation within the qtest accelerator.
>>>
>>> Signed-off-by: David Gibson <address@hidden>
>>> Reviewed-by: Laurent Vivier <address@hidden>
>>> Reviewed-by: Greg Kurz <address@hidden>
>>> ---
>>>  tests/libqos/pci-pc.c    | 38 --------------------------------------
>>>  tests/libqos/pci-spapr.c | 44 --------------------------------------------
>>>  tests/libqos/pci.c       | 20 ++++++++++++++------
>>>  tests/libqos/pci.h       |  8 --------
>>>  4 files changed, 14 insertions(+), 96 deletions(-)
>>>
>>
>> [...]
>>
>>> diff --git a/tests/libqos/pci.h b/tests/libqos/pci.h
>>> index 2b08362..ce6ed08 100644
>>> --- a/tests/libqos/pci.h
>>> +++ b/tests/libqos/pci.h
>>> @@ -27,18 +27,10 @@ struct QPCIBus {
>>>      uint16_t (*pio_readw)(QPCIBus *bus, uint32_t addr);
>>>      uint32_t (*pio_readl)(QPCIBus *bus, uint32_t addr);
>>>  
>>> -    uint8_t (*mmio_readb)(QPCIBus *bus, uint32_t addr);
>>> -    uint16_t (*mmio_readw)(QPCIBus *bus, uint32_t addr);
>>> -    uint32_t (*mmio_readl)(QPCIBus *bus, uint32_t addr);
>>> -
>>>      void (*pio_writeb)(QPCIBus *bus, uint32_t addr, uint8_t value);
>>>      void (*pio_writew)(QPCIBus *bus, uint32_t addr, uint16_t value);
>>>      void (*pio_writel)(QPCIBus *bus, uint32_t addr, uint32_t value);
>>>  
>>> -    void (*mmio_writeb)(QPCIBus *bus, uint32_t addr, uint8_t value);
>>> -    void (*mmio_writew)(QPCIBus *bus, uint32_t addr, uint16_t value);
>>> -    void (*mmio_writel)(QPCIBus *bus, uint32_t addr, uint32_t value);
>>> -
>>>      void (*memread)(QPCIBus *bus, uint32_t addr, void *buf, size_t len);
>>>      void (*memwrite)(QPCIBus *bus, uint32_t addr, const void *buf, size_t 
>>> len);
>>>  
>>>
>>
>> You added them in "libqos: Handle PCI IO de-multiplexing in common code"
>> (few patched before) and removing them now - if you moved this patch
>> earlier, it would reduce the series, or what do I miss?
> 
> Well, it can't go before the PIO / MMIO split, because on x86 the PIO
> part is implemented with inw/outw instead of readw/writew, and those
> don't have a memread/memwrite equivalent.
> 
> The change could go at the same time, but my feeling was that logical
> separation of the steps was worth a bit of temporary extra code.

It is a bit hard to follow the logic of the patchset when you do not know
if the new code is going to stay or not - I automatically assumed it is
staying and when I saw it is being removed - I wondered if you are removing
what you just added, and this - in my opinion - kills the idea of making
smaller patches to make review easier, better just squash them all... But
since Greg is happy and things seems not working worse (make check fails on
my setup but whatever), you can ignore me :)


-- 
Alexey

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