linux-kernel - Re: [PATCH v11 2/3] tty: hvc: pass DMA capable memory to put

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Message-ID: <YXelB/WhWPqcIl/T@kroah.com>
Date:   Tue, 26 Oct 2021 08:49:43 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xianting Tian <xianting.tian@...ux.alibaba.com>
Cc:     Jiri Slaby <jirislaby@...nel.org>, amit@...nel.org, arnd@...db.de,
        osandov@...com, shile.zhang@...ux.alibaba.com,
        linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 2/3] tty: hvc: pass DMA capable memory to put_chars()

On Tue, Oct 26, 2021 at 02:11:51PM +0800, Xianting Tian wrote:
> 
> 在 2021/10/26 下午2:10, Greg KH 写道:
> > On Tue, Oct 26, 2021 at 02:02:21PM +0800, Xianting Tian wrote:
> > > 在 2021/10/26 下午1:10, Jiri Slaby 写道:
> > > > On 15. 10. 21, 4:46, Xianting Tian wrote:
> > > > > @@ -151,9 +142,11 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
> > > > >    static void hvc_console_print(struct console *co, const char *b,
> > > > >                      unsigned count)
> > > > >    {
> > > > > -    char c[N_OUTBUF] __ALIGNED__;
> > > > > +    char *c;
> > > > >        unsigned i = 0, n = 0;
> > > > >        int r, donecr = 0, index = co->index;
> > > > > +    unsigned long flags;
> > > > > +    struct hvc_struct *hp;
> > > > >          /* Console access attempt outside of acceptable console
> > > > > range. */
> > > > >        if (index >= MAX_NR_HVC_CONSOLES)
> > > > > @@ -163,6 +156,13 @@ static void hvc_console_print(struct console
> > > > > *co, const char *b,
> > > > >        if (vtermnos[index] == -1)
> > > > >            return;
> > > > >    +    hp = cons_hvcs[index];
> > > > > +    if (!hp)
> > > > > +        return;
> > > > You effectively make the console unusable until someone calls
> > > > hvc_alloc() for this device, correct? This doesn't look right. Neither
> > > > you describe this change of behaviour in the commit log.
> > > I mentioned such info in the commit log:
> > > 'Introduce another array(cons_hvcs[]) for hvc pointers next to the
> > > cons_ops[] and vtermnos[] arrays. With the array, we can easily find
> > > hvc's cons_outbuf and its lock.'
> > > 
> > > After you pointed it out, I just found what you said make sense, I checked the code hvc_console_print() can support print before hvc_alloc() is called when someone use hvc_instantiate() for an early console discovery method.
> > > I send a patch to fix the issue?  or these serial pathches reverted fisrtly then I resend new version patches? thanks
> > Let me revert these now and you can send an updated version.
> OK, thanks.

I have now reverted patches 2/3 and 3/3 in this series from my tree.
The first patch was just fine.

thanks,

greg k-h