Re: [PATCH v2 2/4] vhost-user: introduce virtio API

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Aug 14, 2024 at 02:47:36PM +0200, Laurent Vivier wrote:
> On 17/07/2024 07:21, David Gibson wrote:
> > On Fri, Jul 12, 2024 at 05:32:42PM +0200, Laurent Vivier wrote:
> > > Add virtio.c and virtio.h that define the functions needed
> > > to manage virtqueues.
> > > 
> > > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> > > ---
> > >   Makefile |   4 +-
> > >   util.h   |  11 +
> > >   virtio.c | 611 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >   virtio.h | 190 +++++++++++++++++
> > >   4 files changed, 814 insertions(+), 2 deletions(-)
> > >   create mode 100644 virtio.c
> > >   create mode 100644 virtio.h
> > > 
> ...
> > > +
> > > +/**
> > > + * struct vu_dev_region - guest shared memory region
> > > + * @gpa:		Guest physical address of the region
> > > + * @size:		Memory size in bytes
> > > + * @qva:		QEMU virtual address
> > 
> > Is this actually the qemu virtual address? Or is it our virtual
> > address?
> > 
> 
> It is actually QEMU virtual address, it's a virtual address provided by the
> front-end (in our case QEMU).

Ok.

> https://qemu-project.gitlab.io/qemu/interop/vhost-user.html#memory-region-description
> 
> It's used in qva_to_va() to convert vring addresses that are in QEMU
> userspace (vhost-user) to our process userspace mapped address, while
> vu_gpa_to_va() is used to convert guest physical address (virtio) of buffers
> address stored vring descritors that are in guest physical address space to
> our process address space.
> 
> vhost-user addresses are in QEMU virtual adress space, virtio addresses are
> in guest physical address space.
> 
> 
> Thansk,
> Laurent
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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