Re: [Qemu-devel] [PATCH 06/11] spapr: update spapr hotplug documentation

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Oct 12, 2016 at 06:13:54PM -0500, Michael Roth wrote:
> This updates the existing documentation to reflect recent updates to
> the hotplug event structure, which are in draft form but slated
> for inclusion in PAPR/LoPAPR.
> 
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  docs/specs/ppc-spapr-hotplug.txt | 55 +++++++++++++++++++++++++++++++++-------
>  1 file changed, 46 insertions(+), 9 deletions(-)
> 
> diff --git a/docs/specs/ppc-spapr-hotplug.txt b/docs/specs/ppc-spapr-hotplug.txt
> index 631b0ca..f57e2a0 100644
> --- a/docs/specs/ppc-spapr-hotplug.txt
> +++ b/docs/specs/ppc-spapr-hotplug.txt
> @@ -233,12 +233,27 @@ tools by host-level management such as an HMC. This level of management is not
>  applicable to PowerKVM, hence the reason for extending the notification
>  framework to support hotplug events.
>  
> -Note that these events are not yet formally part of the PAPR+ specification,
> -but support for this format has already been implemented in DR-related
> -guest tools such as powerpc-utils/librtas, as well as kernel patches that have
> -been submitted to handle in-kernel processing of memory/cpu-related hotplug
> -events[1], and is planned for formal inclusion is PAPR+ specification. The
> -hotplug-specific payload is QEMU implemented as follows (with all values
> +The format for these EPOW-signalled events is described below under
> +"hotplug/unplug event structure". Note that these events are not
> +formally part of the PAPR+ specification, and have been superseded by a
> +newer format, also described below under "hotplug/unplug event structure",
> +and so are now deemed a "legacy" format. The formats are similar, but the
> +"modern" format contains additional fields/flags, which are denoted for the
> +purposes of this documentation with "#ifdef GUEST_SUPPORTS_MODERN" guards.
> +
> +QEMU should assume support only for "legacy" fields/flags unless the guest
> +advertises support for the "modern" format via ibm,client-architecture-support
> +hcall by setting byte 5, bit 6 of it's ibm,architecture-vec-5 option vector
> +structure (as described by LoPAPR v11, B.6.2.3). As with "legacy" format events,
> +"modern" format events are surfaced to the guest via check-exception RTAS calls,
> +but use a dedicated event source to signal the guest. This event source is
> +advertised to the guest by the addition of a "hot-plug-events" node under
> +"/event-sources" node of the guest's device tree using the standard format
> +described in LoPAPR v11, B.6.12.1.
> +
> +== hotplug/unplug event structure ==
> +
> +The hotplug-specific payload in QEMU is implemented as follows (with all values
>  encoded in big-endian format):
>  
>  struct rtas_event_log_v6_hp {
> @@ -263,14 +278,23 @@ struct rtas_event_log_v6_hp {
>  #define RTAS_LOG_V6_HP_ACTION_ADD       1
>  #define RTAS_LOG_V6_HP_ACTION_REMOVE    2
>      uint8_t hotplug_action;             /* action (add/remove) */
> -#define RTAS_LOG_V6_HP_ID_DRC_NAME      1
> -#define RTAS_LOG_V6_HP_ID_DRC_INDEX     2
> -#define RTAS_LOG_V6_HP_ID_DRC_COUNT     3
> +#define RTAS_LOG_V6_HP_ID_DRC_NAME          1
> +#define RTAS_LOG_V6_HP_ID_DRC_INDEX         2
> +#define RTAS_LOG_V6_HP_ID_DRC_COUNT         3
> +#ifdef GUEST_SUPPORTS_MODERN
> +#define RTAS_LOG_V6_HP_ID_DRC_COUNT_INDEXED 4
> +#endif
>      uint8_t hotplug_identifier;         /* type of the resource identifier,
>                                           * which serves as the discriminator
>                                           * for the 'drc' union field below
>                                           */
> +#ifdef GUEST_SUPPORTS_MODERN
> +    uint8_t capabilities;               /* capability flags, currently unused
> +                                         * by QEMU
> +                                         */
> +#else
>      uint8_t reserved;
> +#endif
>      union {
>          uint32_t index;                 /* DRC index of resource to take action
>                                           * on
> @@ -278,6 +302,19 @@ struct rtas_event_log_v6_hp {
>          uint32_t count;                 /* number of DR resources to take
>                                           * action on (guest chooses which)
>                                           */
> +#ifdef GUEST_SUPPORTS_MODERN
> +        struct {
> +            uint32_t count;             /* number of DR resources to take
> +                                         * action on
> +                                         */
> +            uint32_t index;             /* DRC index of first resource to take
> +                                         * action on. guest will take action
> +                                         * on DRC index <index> through
> +                                         * DRC index <index + count - 1> in
> +                                         * sequential order
> +                                         */
> +        } count_indexed;
> +#endif
>          char name[1];                   /* string representing the name of the
>                                           * DRC to take action on
>                                           */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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