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

[Avi Kivity <avi@redhat.com>]

On 06/11/2010 08:31 PM, Cam Macdonell wrote:
> On Mon, Apr 19, 2010 at 10:41 AM, Cam Macdonell<cam@cs.ualberta.ca>  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).

Is this really the address the guest programmed, or is qemu 
misinterpreting it?

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