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

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Date:   Wed, 27 Sep 2023 09:17:54 +0000
From:   "Gonglei (Arei)" <arei.gonglei@...wei.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Marc Hartmayer <mhartmay@...ux.ibm.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pizhenwei@...edance.com" <pizhenwei@...edance.com>,
        Cornelia Huck <cohuck@...hat.com>
Subject: RE: [PATCH] crypto: virtio-crypto: call finalize with bh disabled



> -----Original Message-----
> From: Halil Pasic [mailto:pasic@...ux.ibm.com]
> Sent: Wednesday, September 27, 2023 12:42 AM
> To: Gonglei (Arei) <arei.gonglei@...wei.com>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>; linux-crypto@...r.kernel.org;
> Marc Hartmayer <mhartmay@...ux.ibm.com>; Michael S. Tsirkin
> <mst@...hat.com>; Jason Wang <jasowang@...hat.com>;
> virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org;
> pizhenwei@...edance.com; Halil Pasic <pasic@...ux.ibm.com>; Cornelia Huck
> <cohuck@...hat.com>
> Subject: Re: [PATCH] crypto: virtio-crypto: call finalize with bh disabled
> 
> [..]
> > --- 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).
> 
You are right.

So I think the core of this question is: Can we call crypto_finalize_request() in the upper half of the interrupt? 
If so, maybe we should introduce a new function, such as lockdep_assert_in_interrupt().

#define lockdep_assert_in_interrupt()                               \
do {                                                           \
       WARN_ON_ONCE(__lockdep_enabled && !in_interrupt());        \
} while (0)

If not, why? 

Herbert, do you have any suggestions? Thanks.


Regards,
-Gonglei

> 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