Re: [Qemu-ppc] [PATCH 6/6] spapr: Clean up DRC set_isolation_state() path

[Michael Roth]

Quoting David Gibson (2017-06-08 00:09:30)
> There are substantial differences in the various paths through
> set_isolation_state(), both for setting to ISOLATED versus UNISOLATED
> state and for logical versus physical DRCs.
> 
> So, split the set_isolation_state() method into isolate() and unisolate()
> methods, and give it different implementations for the two DRC types.
> 
> Factor some minimal common checks, including for valid indicator values
> (which we weren't previously checking) into rtas_set_isolation_state().
> 
> Signed-off-by: David Gibson <address@hidden>
> ---
>  hw/ppc/spapr_drc.c         | 145 
> ++++++++++++++++++++++++++++++++-------------
>  include/hw/ppc/spapr_drc.h |   6 +-
>  2 files changed, 105 insertions(+), 46 deletions(-)
> 
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 9e01d7b..90c0fde 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -46,30 +46,64 @@ uint32_t spapr_drc_index(sPAPRDRConnector *drc)
>          | (drc->id & DRC_INDEX_ID_MASK);
>  }
> 
> -static uint32_t set_isolation_state(sPAPRDRConnector *drc,
> -                                    sPAPRDRIsolationState state)
> +static uint32_t drc_isolate_physical(sPAPRDRConnector *drc)
>  {
> -    trace_spapr_drc_set_isolation_state(spapr_drc_index(drc), state);
> -
>      /* if the guest is configuring a device attached to this DRC, we
>       * should reset the configuration state at this point since it may
>       * no longer be reliable (guest released device and needs to start
>       * over, or unplug occurred so the FDT is no longer valid)
>       */
> -    if (state == SPAPR_DR_ISOLATION_STATE_ISOLATED) {
> -        g_free(drc->ccs);
> -        drc->ccs = NULL;
> -    }
> +    g_free(drc->ccs);
> +    drc->ccs = NULL;
> 
> -    if (state == SPAPR_DR_ISOLATION_STATE_UNISOLATED) {
> -        /* cannot unisolate a non-existent resource, and, or resources
> -         * which are in an 'UNUSABLE' allocation state. (PAPR 2.7, 13.5.3.5)
> -         */
> -        if (!drc->dev ||
> -            drc->allocation_state == SPAPR_DR_ALLOCATION_STATE_UNUSABLE) {
> -            return RTAS_OUT_NO_SUCH_INDICATOR;
> +    drc->isolation_state = SPAPR_DR_ISOLATION_STATE_ISOLATED;
> +
> +    /* if we're awaiting release, but still in an unconfigured state,
> +     * it's likely the guest is still in the process of configuring
> +     * the device and is transitioning the devices to an ISOLATED
> +     * state as a part of that process. so we only complete the
> +     * removal when this transition happens for a device in a
> +     * configured state, as suggested by the state diagram from PAPR+
> +     * 2.7, 13.4
> +     */
> +    if (drc->awaiting_release) {
> +        uint32_t drc_index = spapr_drc_index(drc);
> +        if (drc->configured) {
> +            trace_spapr_drc_set_isolation_state_finalizing(drc_index);
> +            spapr_drc_detach(drc, DEVICE(drc->dev), NULL);
> +        } else {
> +            trace_spapr_drc_set_isolation_state_deferring(drc_index);
>          }
>      }
> +    drc->configured = false;
> +
> +    return RTAS_OUT_SUCCESS;
> +}
> +
> +static uint32_t drc_unisolate_physical(sPAPRDRConnector *drc)
> +{
> +    /* cannot unisolate a non-existent resource, and, or resources
> +     * which are in an 'UNUSABLE' allocation state. (PAPR 2.7,
> +     * 13.5.3.5)
> +     */
> +    if (!drc->dev) {
> +        return RTAS_OUT_NO_SUCH_INDICATOR;
> +    }
> +
> +    drc->isolation_state = SPAPR_DR_ISOLATION_STATE_UNISOLATED;
> +
> +    return RTAS_OUT_SUCCESS;
> +}
> +
> +static uint32_t drc_isolate_logical(sPAPRDRConnector *drc)
> +{
> +    /* if the guest is configuring a device attached to this DRC, we
> +     * should reset the configuration state at this point since it may
> +     * no longer be reliable (guest released device and needs to start
> +     * over, or unplug occurred so the FDT is no longer valid)
> +     */
> +    g_free(drc->ccs);
> +    drc->ccs = NULL;
> 
>      /*
>       * Fail any requests to ISOLATE the LMB DRC if this LMB doesn't
> @@ -81,35 +115,47 @@ static uint32_t set_isolation_state(sPAPRDRConnector 
> *drc,
>       * If the LMB being removed doesn't belong to a DIMM device that is
>       * actually being unplugged, fail the isolation request here.
>       */
> -    if (spapr_drc_type(drc) == SPAPR_DR_CONNECTOR_TYPE_LMB) {
> -        if ((state == SPAPR_DR_ISOLATION_STATE_ISOLATED) &&
> -             !drc->awaiting_release) {
> -            return RTAS_OUT_HW_ERROR;
> -        }
> +    if (spapr_drc_type(drc) == SPAPR_DR_CONNECTOR_TYPE_LMB
> +        && !drc->awaiting_release) {
> +        return RTAS_OUT_HW_ERROR;
>      }
> 
> -    drc->isolation_state = state;
> +    drc->isolation_state = SPAPR_DR_ISOLATION_STATE_ISOLATED;
> 
> -    if (drc->isolation_state == SPAPR_DR_ISOLATION_STATE_ISOLATED) {
> -        /* if we're awaiting release, but still in an unconfigured state,
> -         * it's likely the guest is still in the process of configuring
> -         * the device and is transitioning the devices to an ISOLATED
> -         * state as a part of that process. so we only complete the
> -         * removal when this transition happens for a device in a
> -         * configured state, as suggested by the state diagram from
> -         * PAPR+ 2.7, 13.4
> -         */
> -        if (drc->awaiting_release) {
> -            uint32_t drc_index = spapr_drc_index(drc);
> -            if (drc->configured) {
> -                trace_spapr_drc_set_isolation_state_finalizing(drc_index);
> -                spapr_drc_detach(drc, DEVICE(drc->dev), NULL);
> -            } else {
> -                trace_spapr_drc_set_isolation_state_deferring(drc_index);
> -            }
> +    /* if we're awaiting release, but still in an unconfigured state,
> +     * it's likely the guest is still in the process of configuring
> +     * the device and is transitioning the devices to an ISOLATED
> +     * state as a part of that process. so we only complete the
> +     * removal when this transition happens for a device in a
> +     * configured state, as suggested by the state diagram from PAPR+
> +     * 2.7, 13.4
> +     */
> +    if (drc->awaiting_release) {
> +        uint32_t drc_index = spapr_drc_index(drc);
> +        if (drc->configured) {
> +            trace_spapr_drc_set_isolation_state_finalizing(drc_index);
> +            spapr_drc_detach(drc, DEVICE(drc->dev), NULL);
> +        } else {
> +            trace_spapr_drc_set_isolation_state_deferring(drc_index);

Not sure this is the right patch to do it, but this refactoring does make
it more apparent that the if (drc->configured) checks should get pushed
down into spapr_drc_detach() like the other deferral checks at some point.

(There are 2 locations that do the detach without checking configured,
but you switched out the one in reset() to use spapr_drc_release()
already, and I don't think drc_set_unusable() without first going
through drc_isolate_*() is a transition that PAPR would allow anyway)