lkml.org 
[lkml]   [2009]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCHv5 3/3] vhost_net: a kernel-level virtio server
On Mon, Sep 14, 2009 at 12:08:55PM -0400, Gregory Haskins wrote:
> Michael S. Tsirkin wrote:
> > On Fri, Sep 11, 2009 at 12:00:21PM -0400, Gregory Haskins wrote:
> >> FWIW: VBUS handles this situation via the "memctx" abstraction. IOW,
> >> the memory is not assumed to be a userspace address. Rather, it is a
> >> memctx-specific address, which can be userspace, or any other type
> >> (including hardware, dma-engine, etc). As long as the memctx knows how
> >> to translate it, it will work.
> >
> > How would permissions be handled?
>
> Same as anything else, really. Read on for details.
>
> > it's easy to allow an app to pass in virtual addresses in its own address space.
>
> Agreed, and this is what I do.
>
> The guest always passes its own physical addresses (using things like
> __pa() in linux). This address passed is memctx specific, but generally
> would fall into the category of "virtual-addresses" from the hosts
> perspective.
>
> For a KVM/AlacrityVM guest example, the addresses are GPAs, accessed
> internally to the context via a gfn_to_hva conversion (you can see this
> occuring in the citation links I sent)
>
> For Ira's example, the addresses would represent a physical address on
> the PCI boards, and would follow any kind of relevant rules for
> converting a "GPA" to a host accessible address (even if indirectly, via
> a dma controller).

So vbus can let an application access either its own virtual memory or a
physical memory on a PCI device. My question is, is any application
that's allowed to do the former also granted rights to do the later?

> > But we can't let the guest specify physical addresses.
>
> Agreed. Neither your proposal nor mine operate this way afaict.
>
> HTH
>
> Kind Regards,
> -Greg
>




\
 
 \ /
  Last update: 2009-09-14 18:59    [W:0.218 / U:0.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site