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Subject: Re: [virtio-dev] Re: [PATCH v1] virtio-mmio: Specify wait needed in driver during reset
On Mon, Aug 16, 2021 at 07:04:51PM +0530, Srivatsa Vaddagiri wrote: > * Michael S. Tsirkin <mst@redhat.com> [2021-08-16 07:48:56]: > > > On Mon, Aug 16, 2021 at 12:05:50PM +0530, Srivatsa Vaddagiri wrote: > > > * Michael S. Tsirkin <mst@redhat.com> [2021-08-16 01:35:46]: > > > > > > > So thinking about all this, quite early in the setup process we > > > > have: > > > > > > > > /* Figure out what features the device supports. */ > > > > device_features = dev->config->get_features(dev); > > > > > > > > > > > > isn't this sufficient? this will flush out > > > > all writes and device can defer responding to reads > > > > until reset is complete. > > > > > > Hmm not sure if that's possible in all MMIO devices? I think a while back Jason > > > felt some of the MMIO devices, their registers could act as plain DRAM for > > > reads, which means device can't block such reads? > > > > > > - vatsa > > > > Is it worth bothering about theoretical issues though? Jason what is > > your take? > > What about the case where device reset fails, which may require driver to > initiate reset again or give up on device? Won't the read of features be forever > deferred in that case? > > - vatsa That might be worth addressing but I feel your proposal does not address it sufficiently. > --- > > Qualcomm Innovation Center, Inc. is submitting the attached "feedback" as a > non-member to the virtio-dev mailing list for consideration and inclusion.
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