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Message-ID: <87mvvteabq.fsf@vitty.brq.redhat.com>
Date: Thu, 08 Oct 2015 15:52:57 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Olaf Hering <olaf@...fle.de>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>, gregkh@...uxfoundation.org,
linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
apw@...onical.com, jasowang@...hat.com
Subject: Re: [PATCH 02/10] Drivers: hv: utils: run polling callback always in interrupt context
Olaf Hering <olaf@...fle.de> writes:
> On Thu, Oct 08, Vitaly Kuznetsov wrote:
>
>> > @@ -295,9 +288,6 @@ static int fcopy_on_msg(void *msg, int len)
>> > if (fcopy_transaction.state == HVUTIL_DEVICE_INIT)
>> > return fcopy_handle_handshake(*val);
>> >
>> > - if (fcopy_transaction.state != HVUTIL_USERSPACE_REQ)
>> > - return -EINVAL;
>> > -
>>
>> This particular change seems unrelated and I'm unsure it's safe to
>> remove this check. It is meant to protect against daemon screwing the
>> protocol and writing to the device when it wasn't requested for an
>> action. It is correct to propagate -EINVAL in this case. Or am I missing
>> something and the check is redundant now?
>
> What can happen if there is an odd write request?
I think we don't want to propagate misbehaving daemon's data to the
host -- let's cut it here. E.g. imagine there is no communication going
on and daemon starts writing something to the device. In case we remove
the check we'll be doing fcopy_respond_to_host() for each daemon's write
flooding the host.
> If there is a timeout
> scheduled some return value will be sent to the host. Then the state is
> set to RESET and eventually vmbus_recvpacket will receive something.
> That something will be processed and passed to the daemon.
>
> If there was no timeout scheduled the write will just return.
yes, but after doing fcopy_respond_to_host(). I'd suggest we leave the
check in place, better safe than sorry.
--
Vitaly
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