Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup()

[Xianting Tian]

在 2021/8/2 下午4:40, Jiri Slaby 写道:
> On 02. 08. 21, 10:32, Xianting Tian wrote:
> > 在 2021/8/2 下午3:25, Jiri Slaby 写道:
> > > Hi,
> > >
> > > why is this 2/2? I seem (Lore neither) to find 1/2.
> > You didn't receive 1/2?
> > [PATCH 1/2] tty: hvc: pass DMA capable memory to put_chars()
> > https://lkml.org/lkml/2021/8/1/8 <https://lkml.org/lkml/2021/8/1/8>
>
> Oh, I did, but it's not properly threaded. PLease fix your setup.
Ok, thanks
> > > On 01. 08. 21, 7:16, Xianting Tian wrote:
> > > > hvc framework will never pass stack memory to the put_chars() 
> > > > function,
> > >
> > > Am I blind or missing something?
> > >
> > > hvc_console_print(...)
> > > {
> > >   char c[N_OUTBUF]
> > > ...
> > >   cons_ops[index]->put_chars(vtermnos[index], c, i);
> > >
> > > The same here:
> > >
> > > hvc_poll_put_char(..., char ch)
> > > {
> > > ...
> > >    n = hp->ops->put_chars(hp->vtermno, &ch, 1);
> > >
> > > AFAICS both of them *pass* a pointer to stack variable.
> >
> > yes, I discussed the issue with Arnd before in below thread, you can 
> > get the history, thanks
> >
> > https://lkml.org/lkml/2021/7/27/494 
> > <https://lkml.org/lkml/2021/7/27/494>
>
> So is this a v2? You should have noted that. And what changed from v1 
> too.

I think yes, I should mentioned it in this patch, sorry for that:(

> > > > So the calling of kmemdup() is unnecessary, remove it.
> > > >
> > > > Fixes: c4baad5029 ("virtio-console: avoid DMA from stack")
> > >
> > > This patch doesn't "Fix" -- it reverts the commit. You should've 
> > > CCed the author too.
> >
> > yes, we discussed ther issue in above thread, which we CCed the author.
>
> I don't see any input from the author?
>
>
> Anyway, 1/2 does not even build, so you will send v3 with all the 
> above fixed, hopefully.

yes, I will send v3 patch after I figured out a better solution based on 
Arnd's comments for the patch '1/2'.

Do you have any other suggestion for the solution?

thanks.

> thanks,