Re: [PATCH v2 6/7] vdpa: move iova_tree allocation to net_vhost_vdpa_init

[Si-Wei Liu]

Hi Michael,

On 2/13/2024 2:22 AM, Michael S. Tsirkin wrote:
> On Mon, Feb 05, 2024 at 05:10:36PM -0800, Si-Wei Liu wrote:
> > Hi Eugenio,
> >
> > I thought this new code looks good to me and the original issue I saw with
> > x-svq=on should be gone. However, after rebase my tree on top of this,
> > there's a new failure I found around setting up guest mappings at early
> > boot, please see attached the specific QEMU config and corresponding event
> > traces. Haven't checked into the detail yet, thinking you would need to be
> > aware of ahead.
> >
> > Regards,
> > -Siwei
> Eugenio were you able to reproduce? Siwei did you have time to
> look into this?
Didn't get a chance to look into the detail yet in the past week, but 
thought it may have something to do with the (internals of) iova tree 
range allocation and the lookup routine. It started to fall apart at the 
first vhost_vdpa_dma_unmap call showing up in the trace events, where it 
should've gotten IOVA=0x2000001000,  but an incorrect IOVA address 
0x1000 was ended up returning from the iova tree lookup routine.

HVA                    GPA                IOVA
-------------------------------------------------------------------------------------------------------------------------
Map
[0x7f7903e00000, 0x7f7983e00000)    [0x0, 0x80000000) [0x1000, 0x80000000)
[0x7f7983e00000, 0x7f9903e00000)    [0x100000000, 0x2080000000) 
[0x80001000, 0x2000001000)
[0x7f7903ea0000, 0x7f7903ec0000)    [0xfeda0000, 0xfedc0000) 
[0x2000001000, 0x2000021000)

Unmap
[0x7f7903ea0000, 0x7f7903ec0000)    [0xfeda0000, 0xfedc0000) [0x1000, 
0x20000) ???
                                    shouldn't it be [0x2000001000, 
0x2000021000) ???

PS, I will be taking off from today and for the next two weeks. Will try 
to help out looking more closely after I get back.

-Siwei
>   Can't merge patches which are known to break things ...