RE: [PATCH] crypto: virtio-crypto: call finalize with bh disabled

[Gonglei (Arei)]

> -----Original Message-----
> From: Michael S. Tsirkin [mailto:mst@xxxxxxxxxx]
> Sent: Wednesday, September 27, 2023 1:14 AM
> To: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Cc: Gonglei (Arei) <arei.gonglei@xxxxxxxxxx>; Herbert Xu
> <herbert@xxxxxxxxxxxxxxxxxxx>; linux-crypto@xxxxxxxxxxxxxxx; Marc
> Hartmayer <mhartmay@xxxxxxxxxxxxx>; Jason Wang
> <jasowang@xxxxxxxxxx>; virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; pizhenwei@xxxxxxxxxxxxx; Cornelia Huck
> <cohuck@xxxxxxxxxx>
> Subject: Re: [PATCH] crypto: virtio-crypto: call finalize with bh disabled
> 
> On Tue, Sep 26, 2023 at 06:41:58PM +0200, Halil Pasic wrote:
> > [..]
> > > --- a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> > > +++ b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
> > > @@ -61,8 +61,9 @@ static void virtio_crypto_akcipher_finalize_req(
> > >  	vc_akcipher_req->src_buf = NULL;
> > >  	vc_akcipher_req->dst_buf = NULL;
> > >  	virtcrypto_clear_request(&vc_akcipher_req->base);
> > > -
> > > +	local_bh_disable();
> > >
> > > crypto_finalize_akcipher_request(vc_akcipher_req->base.dataq->engine
> > > , req, err);
> > > +	local_bh_enable();
> >
> > Thanks Gonglei!
> >
> > I did this a quick spin, and it does not seem to be sufficient on s390x.
> > Which does not come as a surprise to me, because
> >
> > #define lockdep_assert_in_softirq()
> \
> > do
> {
>      \
> >         WARN_ON_ONCE(__lockdep_enabled                  &&
> \
> >                      (!in_softirq() || in_irq() || in_nmi()));          \
> > } while (0)
> >
> > will still warn because  in_irq() still evaluates to true (your patch
> > addresses the !in_softirq() part).
> >
> > I don't have any results on x86 yet. My current understanding is that
> > the virtio-pci transport code disables interrupts locally somewhere in
> > the call chain (actually in vp_vring_interrupt() via
> > spin_lock_irqsave()) and then x86 would be fine. But I will get that verified.
> >
> > On the other hand virtio_airq_handler() calls vring_interrupt() with
> > interrupts enabled. (While vring_interrupt() is called in a (read)
> > critical section in virtio_airq_handler() we use read_lock() and not
> > read_lock_irqsave() to grab the lock. Whether that is correct in it
> > self (i.e. disregarding the crypto problem) or not I'm not sure right
> > now. Will think some more about it tomorrow.) If the way to go forward
> > is disabling interrupts in virtio-ccw before vring_interrupt() is
> > called, I would be glad to spin a patch for that.
> >
> > Copying Conny, as she may have an opinion on this (if I'm not wrong
> > she authored that code).
> >
> > Regards,
> > Halil
> 
> On a related note, config change callback is also handled incorrectly in this
> driver, it takes a mutex from interrupt context.

Good catch. Will fix it.

Thanks.
-Gonglei