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Date: Fri, 27 Feb 2015 15:22:09 +0530
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From: Bharata B Rao <bharata.rao@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH v6 02/15] spapr_drc: initial implementation
 of sPAPRDRConnector device
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To: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: aik@ozlabs.ru, Alexander Graf <agraf@suse.de>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, ncmike@ncultra.org, "qemu-ppc@nongnu.org" <qemu-ppc@nongnu.org>, tyreld@linux.vnet.ibm.com, Nathan Fontenot <nfont@linux.vnet.ibm.com>, David Gibson <david@gibson.dropbear.id.au>

On Fri, Feb 27, 2015 at 8:41 AM, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> +static void attach(sPAPRDRConnector *drc, DeviceState *d, void *fdt,
> +                   int fdt_start_offset, bool coldplug, Error **errp)
> +{
> +    DPRINTFN("drc: %x, attach", get_index(drc));
> +
> +    if (drc->isolation_state != SPAPR_DR_ISOLATION_STATE_ISOLATED) {
> +        error_setg(errp, "an attached device is still awaiting release");
> +        return;
> +    }
> +    g_assert(drc->allocation_state == SPAPR_DR_ALLOCATION_STATE_UNUSABLE);
> +    g_assert(fdt || coldplug);
> +
> +    /* NOTE: setting initial isolation state to UNISOLATED means we can't
> +     * detach unless guest has a userspace/kernel that moves this state
> +     * back to ISOLATED in response to an unplug event, or this is done
> +     * manually by the admin prior. if we force things while the guest
> +     * may be accessing the device, we can easily crash the guest, so we
> +     * we defer completion of removal in such cases to the reset() hook.
> +     */
> +    drc->isolation_state = SPAPR_DR_ISOLATION_STATE_UNISOLATED;
> +    drc->allocation_state = SPAPR_DR_ALLOCATION_STATE_USABLE;

BTW shouldn't isolation_state and allocation_state be set to
UNISOLATED and USABLE in response to guest's rtas-set-indicator calls
? At least, that is how it is done/expected for CPU hotplug case. Ref:
kernel code arch/powerpc/platforms/pseries/dlpar.c:
dlpar_acquire[release]_drc().

Same question for detach().

Regards,
Bharata.