Re: gnumach memory attributes
On Sat, Nov 19, 2016 at 02:37:45PM +0100, Luca dariz wrote:
> I was thinking about what kind of memory addresses should be allowed to
> be translated to physical addresses from user-space drivers, for example
> based on rump kernel.
> Obviously memory allocated with vm_allocate_contiguous from dde patch,
> so from the DIRECTMAP segment and of type VM_PT_KERNEL. Are there other
> possibilities or other parameters to check?
The two major types of memory are anonymous and "file", where file means
that a memory object isn't backed by the default pager. These shouldn't
be affected by what you're trying to do.
Other than that, device memory can easily become driver-specific.
And by the way, please ignore the VM_PT_XXX types, they're not actually
> I am thinking about adding an rpc to handle vitual to physical
> translations (instead of using the debug interface) and maybe rework the
> vm_allocate_contiguous rpc to not give the physical address, making it
> similar to vm_allocate.
What we'd rather have is something like hugetlbfs, where contiguous
physical memory is backed by a pager (probably in the kernel), and
applications would use vm_map to get access.