Re: [Qemu-devel] [PATCH RFC 1/1] KVM: s390: Add MEMOP ioctl for reading/writing guest memory

[Paolo Bonzini]

On 03/02/2015 16:16, Thomas Huth wrote:
> Actually, I'd prefer to keep the "virtual" in the defines for the type
> of operation below: When it comes to s390 storage keys, we likely might
> need some calls for reading and writing to physical memory, too. Then
> we could simply extend this ioctl instead of inventing a new one.

Can you explain why it is necessary to read/write physical addresses
from user space?  In the case of QEMU, I'm worried that you would have
to invent your own memory read/write APIs that are different from
everything else.

On real s390 zPCI, does bus-master DMA update storage keys?

>> Not really true, as you don't check it.  So "It is not used by KVM with
>> the currently defined set of flags" is a better explanation.
> 
> ok ... and maybe add "should be set to zero" ?

If you don't check it, it is misleading to document this.

Paolo