linux-kernel - Re: [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening

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Message-ID: <20200629190644.hlem6jskyx26csaj@liuwe-devbox-debian-v2>
Date:   Mon, 29 Jun 2020 19:06:44 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Andres Beltran <t-mabelt@...rosoft.com>
Cc:     Wei Liu <wei.liu@...nel.org>, Andres Beltran <lkmlabelt@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>
Subject: Re: [PATCH 1/3] Drivers: hv: vmbus: Add vmbus_requestor data
 structure for VMBus hardening

On Mon, Jun 29, 2020 at 06:19:46PM +0000, Andres Beltran wrote:
[...]
> > >  EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
> > > +
> > > +/*
> > > + * vmbus_next_request_id - Returns a new request id. It is also
> > > + * the index at which the guest memory address is stored.
> > > + * Uses a spin lock to avoid race conditions.
> > > + * @rqstor: Pointer to the requestor struct
> > > + * @rqst_add: Guest memory address to be stored in the array
> > > + */
> > > +u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
> > > +{
> > > +	unsigned long flags;
> > > +	u64 current_id;
> > > +
> > > +	spin_lock_irqsave(&rqstor->req_lock, flags);
> > 
> > Do you really need the irqsave variant here? I.e. is there really a
> > chance this code is reachable from an interrupt handler?
> 
> Other VMBus drivers will also need to use this functionality, and
> some of them will be called with interrupts disabled. So, I think
> we should keep the irqsave variant here.
> 

Okay. This makes sense.

Wei.