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Re: [PATCH 6/6] xive: Don't use CPU_FOREACH() to perform CAM line matchi
From: |
David Gibson |
Subject: |
Re: [PATCH 6/6] xive: Don't use CPU_FOREACH() to perform CAM line matching |
Date: |
Thu, 24 Oct 2019 14:05:36 +1100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Wed, Oct 23, 2019 at 04:52:27PM +0200, Greg Kurz wrote:
> Now that the TCTX objects are children of the XIVE router, stop
> using CPU_FOREACH() when looking for a matching VCPU target.
>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> hw/intc/xive.c | 100
> +++++++++++++++++++++++++++++++++++---------------------
> 1 file changed, 62 insertions(+), 38 deletions(-)
>
> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
> index 40ce43152456..ec5e7d0ee39a 100644
> --- a/hw/intc/xive.c
> +++ b/hw/intc/xive.c
> @@ -1403,55 +1403,79 @@ typedef struct XiveTCTXMatch {
> uint8_t ring;
> } XiveTCTXMatch;
>
> -static bool xive_presenter_match(XiveRouter *xrtr, uint8_t format,
> - uint8_t nvt_blk, uint32_t nvt_idx,
> - bool cam_ignore, uint8_t priority,
> - uint32_t logic_serv, XiveTCTXMatch *match)
> +typedef struct XivePresenterMatch {
> + uint8_t format;
> + uint8_t nvt_blk;
> + uint32_t nvt_idx;
> + bool cam_ignore;
> + uint8_t priority;
> + uint32_t logic_serv;
> + XiveTCTXMatch *match;
> + int count;
> +} XivePresenterMatch;
> +
> +static int do_xive_presenter_match(Object *child, void *opaque)
> {
> - CPUState *cs;
> + XiveTCTX *tctx = XIVE_TCTX(child);
> + XivePresenterMatch *xpm = opaque;
> + int ring;
>
> /*
> * TODO (PowerNV): handle chip_id overwrite of block field for
> * hardwired CAM compares
> */
>
> - CPU_FOREACH(cs) {
> - XiveTCTX *tctx = xive_router_get_tctx(xrtr, cs);
> - int ring;
> + /*
> + * HW checks that the CPU is enabled in the Physical Thread
> + * Enable Register (PTER).
> + */
>
> - /*
> - * Skip partially initialized vCPUs. This can happen when
> - * vCPUs are hotplugged.
> - */
> - if (!tctx) {
> - continue;
> + /*
> + * Check the thread context CAM lines and record matches. We
> + * will handle CPU exception delivery later
> + */
> + ring = xive_presenter_tctx_match(tctx, xpm->format, xpm->nvt_blk,
> + xpm->nvt_idx, xpm->cam_ignore,
> + xpm->logic_serv);
> +
> + /*
> + * Save the context and follow on to catch duplicates, that we
> + * don't support yet.
> + */
> + if (ring != -1) {
> + if (xpm->match->tctx) {
> + qemu_log_mask(LOG_GUEST_ERROR, "XIVE: already found a thread "
> + "context NVT %x/%x\n", xpm->nvt_blk, xpm->nvt_idx);
> + return -1;
> }
>
> - /*
> - * HW checks that the CPU is enabled in the Physical Thread
> - * Enable Register (PTER).
> - */
> + xpm->match->ring = ring;
> + xpm->match->tctx = tctx;
> + xpm->count++;
> + }
>
> - /*
> - * Check the thread context CAM lines and record matches. We
> - * will handle CPU exception delivery later
> - */
> - ring = xive_presenter_tctx_match(tctx, format, nvt_blk, nvt_idx,
> - cam_ignore, logic_serv);
> - /*
> - * Save the context and follow on to catch duplicates, that we
> - * don't support yet.
> - */
> - if (ring != -1) {
> - if (match->tctx) {
> - qemu_log_mask(LOG_GUEST_ERROR, "XIVE: already found a thread
> "
> - "context NVT %x/%x\n", nvt_blk, nvt_idx);
> - return false;
> - }
> -
> - match->ring = ring;
> - match->tctx = tctx;
> - }
> + return 0;
> +}
> +
> +static bool xive_presenter_match(XiveRouter *xrtr, uint8_t format,
> + uint8_t nvt_blk, uint32_t nvt_idx,
> + bool cam_ignore, uint8_t priority,
> + uint32_t logic_serv, XiveTCTXMatch *match)
> +{
> + XivePresenterMatch xpm = {
> + .format = format,
> + .nvt_blk = nvt_blk,
> + .nvt_idx = nvt_idx,
> + .cam_ignore = cam_ignore,
> + .priority = priority,
> + .logic_serv = logic_serv,
> + .match = match,
> + .count = 0,
> + };
> +
> + if (object_child_foreach_type(OBJECT(xrtr), TYPE_XIVE_TCTX,
> + do_xive_presenter_match, &xpm) < 0) {
> + return false;
Hrm... xive_presenter_match() is potentially a pretty hot path, it's
called on every interrupt delivery - especially since we don't have a
usable KVM irq chip for Boston machines. I'm concerned that using
something as heavyweight as object_child_foreach() might have a
noticeable performance impact.
> }
>
> if (!match->tctx) {
>
--
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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[PATCH 6/6] xive: Don't use CPU_FOREACH() to perform CAM line matching, Greg Kurz, 2019/10/23
- Re: [PATCH 6/6] xive: Don't use CPU_FOREACH() to perform CAM line matching,
David Gibson <=
[PATCH 5/6] spapr: Don't use CPU_FOREACH() in 'info pic', Greg Kurz, 2019/10/23