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

[Avi Kivity]

On 06/25/2010 12:51 AM, Cam Macdonell wrote:
> 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
>    

So the address c20000000000 is illegal.

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

Well, what's the answer?

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