Re: [Qemu-devel] [PATCH 2/2] hw/pci-host/x86: extend the 64-bit PCI hole relative to the fw-assigned base

[Laszlo Ersek]

On 09/27/18 11:21, Laszlo Ersek wrote:
> On 09/27/18 07:48, Gerd Hoffmann wrote:
>>   Hi,
>>
>>>> Maybe using memdev file backend with manually created sparse file
>>>> might actually work (with preallocate disabled)
>>>
>>> Thanks, this sounds like a good idea.
>>>
>>> I see shm_open() is used heavily in ivshmem-related tests. I haven't
>>> looked much at shm_open() before. (I've always known it existed in
>>> POSIX, but I've never cared.)
>>
>> How about improving the lovely pci-testdev we have a bit?  Then we can
>> have huge pci bars without needing backing storage for them ...
> 
> Earlier I checked
> 
>   qemu-system-x86_64 -device pci-testdev,\?
> 
> briefly. I didn't see anything relevant and figured it was out of scope.
> 
> (
> Actually, I've thought of yet another thing: the resource reservation
> capability for PCIe Root Ports. The 64-bit reservation field in that cap
> structure should be perfectly suitable for this testing.
> 
> Except, of course, SeaBIOS only handles the bus number reservation
> field, at this time. :/
> )
> 
> Looking at "docs/specs/pci-testdev.txt" now, extending the PCI testdev
> looks like a separate project to me. We're getting quite far from the
> original goal. I totally agree that if the PCI testdev already had this
> ability, it would be a perfect fit, but I don't think I can personally
> take that on now.

I realize you pasted a prototype patch below (thanks for that!), but it
doesn't update the documentation. I wouldn't like to dig down another
design rabbit hole here.

If you can pursue upstreaming this change, I can definitely delay my
series, and use the enhanced pci testdev as a reproducer. But, I'm not
explicitly asking you to pursue it -- none of this classifies as a
"serious bug", so these patches might not be the best uses of our times.

Laszlo

>> =========================== cut here ===========================
>> From 05cfced149b0b5c953391666c3151034bc7fe88b Mon Sep 17 00:00:00 2001
>> From: Gerd Hoffmann <address@hidden>
>> Date: Thu, 27 Sep 2018 07:43:10 +0200
>> Subject: [PATCH] pci-testdev: add optional memory bar
>>
>> Add memory bar to pci-testdev.  Size is configurable using the membar
>> property.  Setting the size to zero (default) turns it off.
>>
>> Signed-off-by: Gerd Hoffmann <address@hidden>
>> ---
>>  hw/misc/pci-testdev.c | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/hw/misc/pci-testdev.c b/hw/misc/pci-testdev.c
>> index 32041f535f..af4d678ee4 100644
>> --- a/hw/misc/pci-testdev.c
>> +++ b/hw/misc/pci-testdev.c
>> @@ -85,6 +85,9 @@ typedef struct PCITestDevState {
>>      MemoryRegion portio;
>>      IOTest *tests;
>>      int current;
>> +
>> +    size_t membar_size;
>> +    MemoryRegion membar;
>>  } PCITestDevState;
>>  
>>  #define TYPE_PCI_TEST_DEV "pci-testdev"
>> @@ -253,6 +256,15 @@ static void pci_testdev_realize(PCIDevice *pci_dev, 
>> Error **errp)
>>      pci_register_bar(pci_dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY, &d->mmio);
>>      pci_register_bar(pci_dev, 1, PCI_BASE_ADDRESS_SPACE_IO, &d->portio);
>>  
>> +    if (d->membar_size) {
>> +        memory_region_init(&d->membar, OBJECT(d), "membar", d->membar_size);
>> +        pci_register_bar(pci_dev, 2,
>> +                         PCI_BASE_ADDRESS_SPACE_MEMORY |
>> +                         PCI_BASE_ADDRESS_MEM_PREFETCH |
>> +                         PCI_BASE_ADDRESS_MEM_TYPE_64,
>> +                         &d->membar);
>> +    }
>> +
>>      d->current = -1;
>>      d->tests = g_malloc0(IOTEST_MAX * sizeof *d->tests);
>>      for (i = 0; i < IOTEST_MAX; ++i) {
>> @@ -305,6 +317,11 @@ static void qdev_pci_testdev_reset(DeviceState *dev)
>>      pci_testdev_reset(d);
>>  }
>>  
>> +static Property pci_testdev_properties[] = {
>> +    DEFINE_PROP_SIZE("membar", PCITestDevState, membar_size, 0),
>> +    DEFINE_PROP_END_OF_LIST(),
>> +};
>> +
>>  static void pci_testdev_class_init(ObjectClass *klass, void *data)
>>  {
>>      DeviceClass *dc = DEVICE_CLASS(klass);
>> @@ -319,6 +336,7 @@ static void pci_testdev_class_init(ObjectClass *klass, 
>> void *data)
>>      dc->desc = "PCI Test Device";
>>      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>>      dc->reset = qdev_pci_testdev_reset;
>> +    dc->props = pci_testdev_properties;
>>  }
>>  
>>  static const TypeInfo pci_testdev_info = {
>>
>