[Qemu-devel] Re: Unusual physical address when using 64-bit BAR

[Cam Macdonell]

On Tue, Jun 15, 2010 at 5:04 AM, Avi Kivity <address@hidden> wrote:
> On 06/11/2010 08:31 PM, Cam Macdonell wrote:
>>
>> On Mon, Apr 19, 2010 at 10:41 AM, Cam Macdonell<address@hidden>
>>  wrote:
>>
>>>
>>> Hi,
>>>
>>> I'm trying to use a 64-bit BAR for my shared memory device.  In simply
>>> changing the memory type in pci_register_bar() to
>>> PCI_BASE_ADDRESS_MEM_TYPE_64 I get an unusual physical address for
>>> that BAR (and my driver crashes in pci_ioremap).
>>>
>>> from lspci:
>>>
>>> 00:04.0 RAM memory: Qumranet, Inc. Device 1110
>>>        Subsystem: Qumranet, Inc. Device 1100
>>>        Flags: fast devsel, IRQ 10
>>>        Memory at f1020000 (32-bit, non-prefetchable) [size=1K]
>>>        Memory at f1021000 (32-bit, non-prefetchable) [size=4K]
>>>        Memory at c20000000000 (64-bit, non-prefetchable) [size=1024M]
>>>        Capabilities:<access denied>
>>> 00: f4 1a 10 11 03 00 10 00 00 00 00 05 00 00 00 00
>>> 10: 00 00 02 f1 00 10 02 f1 04 00 00 00 00 c2 00 00
>>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 f4 1a 00 11
>>> 30: 00 00 00 00 40 00 00 00 00 00 00 00 0b 01 00 00
>>>
>>> with DEBUG_MEMREG, I see
>>>
>>> kvm_unregister_memory_area:666 Unregistering memory region
>>> c20000000000 (40000000)
>>> kvm_destroy_phys_mem:649 slot 7 start c20000000000 len 0 flags 0
>>> IVSHMEM: addr = 3221225472 size = 1073741824
>>> kvm_register_phys_mem:605 memory: gpa: c200c0000000, size: 40000000,
>>> uaddr: 7f6dd7ffe000, slot: 7, flags: 0
>>> kvm_unregister_memory_area:666 Unregistering memory region
>>> c200c0000000 (40000000)
>>> kvm_destroy_phys_mem:649 slot 7 start c200c0000000 len 0 flags 0
>>> IVSHMEM: addr = 0 size = 1073741824
>>> kvm_register_phys_mem:605 memory: gpa: c20000000000, size: 40000000,
>>> uaddr: 7f6dd7ffe000, slot: 7, flags: 0
>>> kvm_unregister_memory_area:666 Unregistering memory region
>>> c20000000000 (40000000)
>>> kvm_destroy_phys_mem:649 slot 7 start c20000000000 len 0 flags 0
>>> IVSHMEM: addr = 0 size = 1073741824
>>> kvm_register_phys_mem:605 memory: gpa: ffffffff00000000, size:
>>> 40000000, uaddr: 7f6dd7ffe000, slot: 7, flags: 0
>>> kvm_unregister_memory_area:666 Unregistering memory region
>>> ffffffff00000000 (40000000)
>>> kvm_destroy_phys_mem:649 slot 7 start ffffffff00000000 len 0 flags 0
>>> IVSHMEM: addr = 0 size = 1073741824
>>> kvm_register_phys_mem:605 memory: gpa: c20000000000, size: 40000000,
>>> uaddr: 7f6dd7ffe000, slot: 7, flags: 0
>>>
>>> (the IVSHMEM lines are my debug statements)
>>>
>>> address sizes   : 40 bits physical, 48 bits virtual  (guest)
>>> address sizes   : 38 bits physical, 48 bits virtual  (host)
>>>
>>>
>>
>> Hi, I happened to run into this problem again when trying to use a
>> 64-bit BAR.  I did a bit more digging and the test that is failing is
>> called from arch/x86/mm/ioremap.c in the guest and here it is.
>>
>> static inline int phys_addr_valid(resource_size_t addr)
>> {
>> #ifdef CONFIG_PHYS_ADDR_T_64BIT
>>        return !(addr>>  boot_cpu_data.x86_phys_bits);
>> #else
>>        return 1;
>> #endif
>> }
>>
>> the value of addr (in this case the 48-bit virtual address
>> c20000000000) is shifted to the right shift by
>> boot_cpu_data.x86_phys_bits (which is 40 bits, the physical address
>> size), so a non-zero value is returned which causes the test to fail
>> and generates the "invalid physical address" error in the guest.
>>
>> Any help is appreciated as to whether this is a Qemu or guest kernel
>> issue.
>>
>
> The guest kernel should never have generated an address that is bigger than
> cpu_phys_bits in the first place.  What's the value for cpu_phys_bits in the
> guest? (/proc/cpuinfo, 'address sizes :' line).

Sorry I missed your reply until now.  The guest address sizes are as follows:

address sizes   : 40 bits physical, 48 bits virtual

>
> Is this really the address the guest programmed, or is qemu misinterpreting
> it?
>
> --
> error compiling committee.c: too many arguments to function
>
>