Re: [Qemu-devel] [PATCH v3 23/23] pci: honor PCI_COMMAND_MASTER

[Avi Kivity <avi@redhat.com>]

On 10/11/2012 05:38 AM, liu ping fan wrote:
> On Wed, Oct 10, 2012 at 12:32 AM, Avi Kivity <avi@redhat.com> wrote:
>> Currently we ignore PCI_COMMAND_MASTER completely: DMA succeeds even when
>> the bit is clear.
>>
>> Honor PCI_COMMAND_MASTER by inserting a memory region into the device's
>> bus master address space, and tying its enable status to PCI_COMMAND_MASTER.
>>
>> Tested using
>>
>>   setpci -s 03 COMMAND=3
>>
>> while a ping was running on a NIC in slot 3.  The kernel (Linux) detected
>> the stall and recovered after the command
>>
>>   setpci -s 03 COMMAND=7
>>
>> was issued.
>>
>> Signed-off-by: Avi Kivity <avi@redhat.com>
>> ---
>>  hw/pci.c | 13 +++++++++++--
>>  hw/pci.h |  1 +
>>  2 files changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/pci.c b/hw/pci.c
>> index 8e8e030..7adf61b 100644
>> --- a/hw/pci.c
>> +++ b/hw/pci.c
>> @@ -782,7 +782,11 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
>>          /* FIXME: Make dma_context_fn use MemoryRegions instead, so this path is
>>           * taken unconditionally */
>>          /* FIXME: inherit memory region from bus creator */
>> -        address_space_init(&pci_dev->bus_master_as, get_system_memory());
>> +        memory_region_init_alias(&pci_dev->bus_master_enable_region, "bus master",
>> +                                 get_system_memory(), 0,
>> +                                 memory_region_size(get_system_memory()));
> 
> Could we achieve that  hiding special mr from some address space?  I
> think one approach is to limit the iommu's lookup table, but that is
> the guest's willing.  The other one is use dummy-mr to overlap some
> piece of region of system_memory.
> This method will require changing the render sequence of alias mr.
> 
> diff --git a/memory.c b/memory.c
> index 2f68d67..cf67c66 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -499,6 +499,11 @@ static void render_memory_region(FlatView *view,
> 
>      clip = addrrange_intersection(tmp, clip);
> 
> +    /* Render subregions in priority order. */
> +    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {
> +        render_memory_region(view, subregion, base, clip, readonly);
> +    }
> +
>      if (mr->alias) {
>          int128_subfrom(&base, int128_make64(mr->alias->addr));
>          int128_subfrom(&base, int128_make64(mr->alias_offset));
> @@ -506,11 +511,6 @@ static void render_memory_region(FlatView *view,
>          return;
>      }
> 
> -    /* Render subregions in priority order. */
> -    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {
> -        render_memory_region(view, subregion, base, clip, readonly);
> -    }
> -
> 

I don't really follow.  We don't have any memory region that is both a
container and an alias, so this change has no effect.  Can you describe
what you intend?


-- 
error compiling committee.c: too many arguments to function