As far as I can tell, most if not all of the below comments
have now been addressed in version 8. Please check to
verify this is correct.
-Jonathan Cavitt
-----Original Message-----
From: Tvrtko Ursulin <tvrtko.ursu...@linux.intel.com>
Sent: Friday, October 6, 2023 6:05 AM
To: Cavitt, Jonathan <jonathan.cav...@intel.com>;
intel-gfx@lists.freedesktop.org
Cc: Dutt, Sudeep <sudeep.d...@intel.com>; Chang, Yu bruce
<yu.bruce.ch...@intel.com>; chris.p.wil...@linux.intel.com; Iddamsetty, Aravind
<aravind.iddamse...@intel.com>; Yang, Fei <fei.y...@intel.com>; Shyti, Andi
<andi.sh...@intel.com>; Harrison, John C <john.c.harri...@intel.com>; Das,
Nirmoy <nirmoy....@intel.com>; Krzysztofik, Janusz
<janusz.krzyszto...@intel.com>; Roper, Matthew D <matthew.d.ro...@intel.com>;
jani.nik...@linux.intel.com
Subject: Re: [PATCH v7 2/5] drm/i915: Define and use GuC and CTB TLB
invalidation routines
>
>
> On 06/10/2023 11:11, Tvrtko Ursulin wrote:
> >
> > Hi,
> >
> >
> > Andi asked me to summarize what I think is unaddressed review feedback
> > so far in order to consolidate and enable hopefully things to move
> > forward. So I will try to re-iterate the comments and questions below.
> >
> > But also note that there is a bunch of new valid comments from John
> > against v7 which I will not repeat.
> >
> > On 05/10/2023 20:35, Jonathan Cavitt wrote:
> >> From: Prathap Kumar Valsan <prathap.kumar.val...@intel.com>
> >>
> >> The GuC firmware had defined the interface for Translation Look-Aside
> >> Buffer (TLB) invalidation. We should use this interface when
> >> invalidating the engine and GuC TLBs.
> >> Add additional functionality to intel_gt_invalidate_tlb, invalidating
> >> the GuC TLBs and falling back to GT invalidation when the GuC is
> >> disabled.
> >> The invalidation is done by sending a request directly to the GuC
> >> tlb_lookup that invalidates the table. The invalidation is submitted as
> >> a wait request and is performed in the CT event handler. This means we
> >> cannot perform this TLB invalidation path if the CT is not enabled.
> >> If the request isn't fulfilled in two seconds, this would constitute
> >> an error in the invalidation as that would constitute either a lost
> >> request or a severe GuC overload.
> >> The tlb_lookup table is allocated as an xarray because the set of
> >> pending TLB invalidations may have no upper bound. The consequence of
> >> this is that all actions interfacing with this table need to use the
> >> xarray functions, such as xa_alloc_cyclic_irq for array insertion.
> >>
> >> With this new invalidation routine, we can perform GuC-based GGTT
> >> invalidations. GuC-based GGTT invalidation is incompatible with
> >> MMIO invalidation so we should not perform MMIO invalidation when
> >> GuC-based GGTT invalidation is expected.
> >
> > On the commit message, I was asking that it describes the justification
> > for the complexity patch adds with the wait queue management. It is
> > non-trivial code, open-coded-almost-copy-of wait_token(), etc, so it
> > needs explanation.
> >
> > Today we have all threads serialize their invalidation under
> > gt->tlb.invalidate_lock. With this patch that remains, but it allows a
> > little bit of de-serialization in waiting. I suspect this is because
> > with mmio i915 has direct access to invalidation, where with GuC the
> > requests are competing for latency with other CT requests too (not
> > invalidations).
> >
> > Simpler patch could be doing the same as the GFP_ATOMIC fallback path in
> > guc_send_invalidate_tlb - ie. serialize it all against one CT
> > invalidation "slot". Are the gains of allowing multiple wait slots
> > significant enough to warrant the complexity etc needs to be documented
> > and the above problem space explained in the commit message.
>
> Also, any gains from the invidual waiters are limited to
> ggtt->invalidate() callers right? Because the put_pages invalidations
> are serialized at the top-level in intel_gt_invalidate_tlb_full() anyway.
>
> And how frequent or relevant are ggtt invalidations at runtime? It is
> just context creation and such, no (rings, contexts state)? Are page
> flips / framebuffers relevant too?
>
> Question is whether a simpler scheme, with a single wait queue (no open
> coded wait_token(), xarray etc) and just waking up all waiters on
> processing CT done, where each waiters check the seqno and goes back to
> sleep if it's invalidation hasn't been completed yet, would be sufficient.
>
> Regards,
>
> Tvrtko
>
> >
> >> Signed-off-by: Prathap Kumar Valsan <prathap.kumar.val...@intel.com>
> >> Signed-off-by: Bruce Chang <yu.bruce.ch...@intel.com>
> >> Signed-off-by: Chris Wilson <chris.p.wil...@intel.com>
> >> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.rama...@intel.com>
> >> Signed-off-by: Jonathan Cavitt <jonathan.cav...@intel.com>
> >> Signed-off-by: Aravind Iddamsetty <aravind.iddamse...@intel.com>
> >> Signed-off-by: Fei Yang <fei.y...@intel.com>
> >> CC: Andi Shyti <andi.sh...@linux.intel.com>
> >> ---
> >> drivers/gpu/drm/i915/gt/intel_ggtt.c | 34 ++-
> >> drivers/gpu/drm/i915/gt/intel_tlb.c | 14 +-
> >> .../gpu/drm/i915/gt/uc/abi/guc_actions_abi.h | 33 +++
> >> drivers/gpu/drm/i915/gt/uc/intel_guc.h | 22 ++
> >> drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 4 +
> >> drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h | 1 +
> >> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 211 +++++++++++++++++-
> >> 7 files changed, 307 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c
> >> b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> >> index 4d7d88b92632b..18f23f27f1572 100644
> >> --- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
> >> +++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
> >> @@ -206,22 +206,38 @@ static void gen8_ggtt_invalidate(struct
> >> i915_ggtt *ggtt)
> >> intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6,
> >> GFX_FLSH_CNTL_EN);
> >> }
> >> +static void guc_ggtt_ct_invalidate(struct intel_gt *gt)
> >> +{
> >> + struct intel_uncore *uncore = gt->uncore;
> >> + intel_wakeref_t wakeref;
> >> +
> >> + with_intel_runtime_pm_if_active(uncore->rpm, wakeref) {
> >> + struct intel_guc *guc = >->uc.guc;
> >> +
> >> + intel_guc_invalidate_tlb(guc);
> >> + }
> >> +}
> >> +
> >> static void guc_ggtt_invalidate(struct i915_ggtt *ggtt)
> >> {
> >> struct drm_i915_private *i915 = ggtt->vm.i915;
> >> + struct intel_gt *gt;
> >> - gen8_ggtt_invalidate(ggtt);
> >> -
> >> - if (GRAPHICS_VER(i915) >= 12) {
> >> - struct intel_gt *gt;
> >> + if (!HAS_GUC_TLB_INVALIDATION(i915))
> >> + gen8_ggtt_invalidate(ggtt);
> >> - list_for_each_entry(gt, &ggtt->gt_list, ggtt_link)
> >> + list_for_each_entry(gt, &ggtt->gt_list, ggtt_link) {
> >> + if (HAS_GUC_TLB_INVALIDATION(i915) &&
> >> + intel_guc_is_ready(>->uc.guc)) {
> >> + guc_ggtt_ct_invalidate(gt);
> >> + } else if (GRAPHICS_VER(i915) >= 12) {
> >> intel_uncore_write_fw(gt->uncore,
> >> GEN12_GUC_TLB_INV_CR,
> >> GEN12_GUC_TLB_INV_CR_INVALIDATE);
> >> - } else {
> >> - intel_uncore_write_fw(ggtt->vm.gt->uncore,
> >> - GEN8_GTCR, GEN8_GTCR_INVALIDATE);
> >> + } else {
> >> + intel_uncore_write_fw(gt->uncore,
> >> + GEN8_GTCR, GEN8_GTCR_INVALIDATE);
> >> + }
> >> }
> >> }
> >> @@ -1243,7 +1259,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
> >> ggtt->vm.raw_insert_page = gen8_ggtt_insert_page;
> >> }
> >> - if (intel_uc_wants_guc(&ggtt->vm.gt->uc))
> >> + if (intel_uc_wants_guc_submission(&ggtt->vm.gt->uc))
> >> ggtt->invalidate = guc_ggtt_invalidate;
> >> else
> >> ggtt->invalidate = gen8_ggtt_invalidate;
> >> diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.c
> >> b/drivers/gpu/drm/i915/gt/intel_tlb.c
> >> index 139608c30d978..a84563c178bc6 100644
> >> --- a/drivers/gpu/drm/i915/gt/intel_tlb.c
> >> +++ b/drivers/gpu/drm/i915/gt/intel_tlb.c
> >> @@ -12,6 +12,7 @@
> >> #include "intel_gt_print.h"
> >> #include "intel_gt_regs.h"
> >> #include "intel_tlb.h"
> >> +#include "uc/intel_guc.h"
> >> /*
> >> * HW architecture suggest typical invalidation time at 40us,
> >> @@ -131,11 +132,22 @@ void intel_gt_invalidate_tlb_full(struct
> >> intel_gt *gt, u32 seqno)
> >> return;
> >> with_intel_gt_pm_if_awake(gt, wakeref) {
> >> + struct intel_guc *guc = >->uc.guc;
> >> +
> >> mutex_lock(>->tlb.invalidate_lock);
> >> if (tlb_seqno_passed(gt, seqno))
> >> goto unlock;
> >> - mmio_invalidate_full(gt);
> >> + if (HAS_GUC_TLB_INVALIDATION(gt->i915)) {
> >> + /*
> >> + * Only perform GuC TLB invalidation if GuC is ready.
> >> + * Otherwise, skip invalidation altogeter.
> >> + */
> >> + if (intel_guc_is_ready(guc))
> >> + intel_guc_invalidate_tlb_full(guc);
> >> + } else {
> >> + mmio_invalidate_full(gt);
> >> + }
> >> write_seqcount_invalidate(>->tlb.seqno);
> >> unlock:
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> >> b/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> >> index f359bef046e0b..9dff8012d5e76 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> >> +++ b/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> >> @@ -138,6 +138,8 @@ enum intel_guc_action {
> >> INTEL_GUC_ACTION_REGISTER_CONTEXT_MULTI_LRC = 0x4601,
> >> INTEL_GUC_ACTION_CLIENT_SOFT_RESET = 0x5507,
> >> INTEL_GUC_ACTION_SET_ENG_UTIL_BUFF = 0x550A,
> >> + INTEL_GUC_ACTION_TLB_INVALIDATION = 0x7000,
> >> + INTEL_GUC_ACTION_TLB_INVALIDATION_DONE = 0x7001,
> >> INTEL_GUC_ACTION_STATE_CAPTURE_NOTIFICATION = 0x8002,
> >> INTEL_GUC_ACTION_NOTIFY_FLUSH_LOG_BUFFER_TO_FILE = 0x8003,
> >> INTEL_GUC_ACTION_NOTIFY_CRASH_DUMP_POSTED = 0x8004,
> >> @@ -181,4 +183,35 @@ enum intel_guc_state_capture_event_status {
> >> #define INTEL_GUC_STATE_CAPTURE_EVENT_STATUS_MASK 0x000000FF
> >> +#define INTEL_GUC_TLB_INVAL_TYPE_MASK REG_GENMASK(7, 0)
> >> +#define INTEL_GUC_TLB_INVAL_MODE_MASK REG_GENMASK(11, 8)
> >> +#define INTEL_GUC_TLB_INVAL_FLUSH_CACHE REG_BIT(31)
> >> +
> >> +enum intel_guc_tlb_invalidation_type {
> >> + INTEL_GUC_TLB_INVAL_FULL = 0x0,
> >> + INTEL_GUC_TLB_INVAL_GUC = 0x3,
> >
> > New question - are these names coming from the GuC iface? I find it
> > confusing that full does not include GuC but maybe it is just me. So
> > maybe full should be called GT or something? Although then again it
> > wouldn't be clear GT does not include the GuC.. bummer. GPU? Dunno.
> > Minor confusion I guess so can keep as is.
> >
> >> +};
> >> +
> >> +/*
> >> + * 0: Heavy mode of Invalidation:
> >> + * The pipeline of the engine(s) for which the invalidation is
> >> targeted to is
> >> + * blocked, and all the in-flight transactions are guaranteed to be
> >> Globally
> >> + * Observed before completing the TLB invalidation
> >> + * 1: Lite mode of Invalidation:
> >> + * TLBs of the targeted engine(s) are immediately invalidated.
> >> + * In-flight transactions are NOT guaranteed to be Globally Observed
> >> before
> >> + * completing TLB invalidation.
> >> + * Light Invalidation Mode is to be used only when
> >> + * it can be guaranteed (by SW) that the address translations remain
> >> invariant
> >> + * for the in-flight transactions across the TLB invalidation. In
> >> other words,
> >> + * this mode can be used when the TLB invalidation is intended to
> >> clear out the
> >> + * stale cached translations that are no longer in use. Light
> >> Invalidation Mode
> >> + * is much faster than the Heavy Invalidation Mode, as it does not
> >> wait for the
> >> + * in-flight transactions to be GOd.
> >> + */
> >> +enum intel_guc_tlb_inval_mode {
> >> + INTEL_GUC_TLB_INVAL_MODE_HEAVY = 0x0,
> >> + INTEL_GUC_TLB_INVAL_MODE_LITE = 0x1,
> >> +};
> >> +
> >> #endif /* _ABI_GUC_ACTIONS_ABI_H */
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> >> b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> >> index 6c392bad29c19..d7203ba88b0c0 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> >> @@ -79,6 +79,18 @@ struct intel_guc {
> >> */
> >> atomic_t outstanding_submission_g2h;
> >> + /** @tlb_lookup: xarray to store all pending TLB invalidation
> >> requests */
> >> + struct xarray tlb_lookup;
> >> +
> >> + /**
> >> + * @serial_slot: id to the initial waiter created in tlb_lookup,
> >> + * which is used only when failed to allocate new waiter.
> >> + */
> >> + u32 serial_slot;
> >> +
> >> + /** @next_seqno: the next id (sequence no.) to allocate. */
> >> + u32 next_seqno;
> >> +
> >> /** @interrupts: pointers to GuC interrupt-managing functions. */
> >> struct {
> >> bool enabled;
> >> @@ -296,6 +308,11 @@ struct intel_guc {
> >> #define MAKE_GUC_VER_STRUCT(ver) MAKE_GUC_VER((ver).major,
> >> (ver).minor, (ver).patch)
> >> #define GUC_SUBMIT_VER(guc)
> >> MAKE_GUC_VER_STRUCT((guc)->submission_version)
> >> +struct intel_guc_tlb_wait {
> >> + struct wait_queue_head wq;
> >> + bool busy;
> >> +};
> >> +
> >> static inline struct intel_guc *log_to_guc(struct intel_guc_log *log)
> >> {
> >> return container_of(log, struct intel_guc, log);
> >> @@ -418,6 +435,11 @@ static inline bool intel_guc_is_supported(struct
> >> intel_guc *guc)
> >> return intel_uc_fw_is_supported(&guc->fw);
> >> }
> >> +int intel_guc_invalidate_tlb_full(struct intel_guc *guc);
> >> +int intel_guc_invalidate_tlb(struct intel_guc *guc);
> >> +int intel_guc_tlb_invalidation_done(struct intel_guc *guc, const u32
> >> *hxg,
> >> + u32 size);
> >> +
> >> static inline bool intel_guc_is_wanted(struct intel_guc *guc)
> >> {
> >> return intel_uc_fw_is_enabled(&guc->fw);
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> >> b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> >> index 6e22af31513a5..37b76f9650d04 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> >> @@ -1115,6 +1115,9 @@ static int ct_process_request(struct
> >> intel_guc_ct *ct, struct ct_incoming_msg *r
> >> case INTEL_GUC_ACTION_NOTIFY_EXCEPTION:
> >> ret = intel_guc_crash_process_msg(guc, action);
> >> break;
> >> + case INTEL_GUC_ACTION_TLB_INVALIDATION_DONE:
> >> + ret = intel_guc_tlb_invalidation_done(ct_to_guc(ct), hxg,
> >> request->size);
> >> + break;
> >> default:
> >> ret = -EOPNOTSUPP;
> >> break;
> >> @@ -1186,6 +1189,7 @@ static int ct_handle_event(struct intel_guc_ct
> >> *ct, struct ct_incoming_msg *requ
> >> switch (action) {
> >> case INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_DONE:
> >> case INTEL_GUC_ACTION_DEREGISTER_CONTEXT_DONE:
> >> + case INTEL_GUC_ACTION_TLB_INVALIDATION_DONE:
> >> g2h_release_space(ct, request->size);
> >> }
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> >> b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> >> index b4d56eccfb1f0..a7c9874e122a3 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> >> @@ -22,6 +22,7 @@
> >> /* Payload length only i.e. don't include G2H header length */
> >> #define G2H_LEN_DW_SCHED_CONTEXT_MODE_SET 2
> >> #define G2H_LEN_DW_DEREGISTER_CONTEXT 1
> >> +#define G2H_LEN_DW_INVALIDATE_TLB 1
> >> #define GUC_CONTEXT_DISABLE 0
> >> #define GUC_CONTEXT_ENABLE 1
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> >> b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> >> index 2cce5ec1ff00d..7b484d1573f16 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> >> @@ -1798,9 +1798,11 @@ static void __guc_reset_context(struct
> >> intel_context *ce, intel_engine_mask_t st
> >> void intel_guc_submission_reset(struct intel_guc *guc,
> >> intel_engine_mask_t stalled)
> >> {
> >> + struct intel_guc_tlb_wait *wait;
> >> struct intel_context *ce;
> >> unsigned long index;
> >> unsigned long flags;
> >> + unsigned long i;
> >> if (unlikely(!guc_submission_initialized(guc))) {
> >> /* Reset called during driver load? GuC not yet initialised! */
> >> @@ -1826,6 +1828,14 @@ void intel_guc_submission_reset(struct
> >> intel_guc *guc, intel_engine_mask_t stall
> >> /* GuC is blown away, drop all references to contexts */
> >> xa_destroy(&guc->context_lookup);
> >> +
> >> + /*
> >> + * The full GT reset will have cleared the TLB caches and flushed
> >> the
> >> + * G2H message queue; we can release all the blocked waiters.
> >> + */
> >> + xa_for_each(&guc->tlb_lookup, i, wait) {
> >> + wake_up(&wait->wq);
> >> + }
> >
> > Here I asked if this is safe to do unlocked versus concurrent
> > xa_alloc/xa_erase from the invalidations thread maybe racing with GPU
> > reset.
> >
> >> }
> >> static void guc_cancel_context_requests(struct intel_context *ce)
> >> @@ -1948,6 +1958,49 @@ void intel_guc_submission_reset_finish(struct
> >> intel_guc *guc)
> >> static void destroyed_worker_func(struct work_struct *w);
> >> static void reset_fail_worker_func(struct work_struct *w);
> >> +static int init_tlb_lookup(struct intel_guc *guc)
> >> +{
> >> + struct intel_guc_tlb_wait *wait;
> >> + int err;
> >> +
> >> + if (!HAS_GUC_TLB_INVALIDATION(guc_to_gt(guc)->i915))
> >> + return 0;
> >> +
> >> + xa_init_flags(&guc->tlb_lookup, XA_FLAGS_ALLOC);
> >> +
> >> + wait = kzalloc(sizeof(*wait), GFP_KERNEL);
> >> + if (!wait)
> >> + return -ENOMEM;
> >> +
> >> + init_waitqueue_head(&wait->wq);
> >> +
> >> + /* Preallocate a shared id for use under memory pressure. */
> >> + err = xa_alloc_cyclic_irq(&guc->tlb_lookup, &guc->serial_slot, wait,
> >> + xa_limit_32b, &guc->next_seqno, GFP_KERNEL);
> >> + if (err == -ENOMEM) {
> >> + kfree(wait);
> >> + return err;
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static void fini_tlb_lookup(struct intel_guc *guc)
> >> +{
> >> + struct intel_guc_tlb_wait *wait;
> >> +
> >> + if (!HAS_GUC_TLB_INVALIDATION(guc_to_gt(guc)->i915))
> >> + return;
> >> +
> >> + wait = xa_load(&guc->tlb_lookup, guc->serial_slot);
> >> + if (wait) {
> >> + GEM_BUG_ON(wait->busy);
> >> + kfree(wait);
> >> + }
> >> +
> >> + xa_destroy(&guc->tlb_lookup);
> >> +}
> >> +
> >> /*
> >> * Set up the memory resources to be shared with the GuC (via the GGTT)
> >> * at firmware loading time.
> >> @@ -1966,11 +2019,15 @@ int intel_guc_submission_init(struct intel_guc
> >> *guc)
> >> return ret;
> >> }
> >> + ret = init_tlb_lookup(guc);
> >> + if (ret)
> >> + goto destroy_pool;
> >> +
> >> guc->submission_state.guc_ids_bitmap =
> >> bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID(guc), GFP_KERNEL);
> >> if (!guc->submission_state.guc_ids_bitmap) {
> >> ret = -ENOMEM;
> >> - goto destroy_pool;
> >> + goto destroy_tlb;
> >> }
> >> guc->timestamp.ping_delay = (POLL_TIME_CLKS /
> >> gt->clock_frequency + 1) * HZ;
> >> @@ -1979,9 +2036,10 @@ int intel_guc_submission_init(struct intel_guc
> >> *guc)
> >> return 0;
> >> +destroy_tlb:
> >> + fini_tlb_lookup(guc);
> >> destroy_pool:
> >> guc_lrc_desc_pool_destroy_v69(guc);
> >> -
> >> return ret;
> >> }
> >> @@ -1994,6 +2052,7 @@ void intel_guc_submission_fini(struct intel_guc
> >> *guc)
> >> guc_lrc_desc_pool_destroy_v69(guc);
> >> i915_sched_engine_put(guc->sched_engine);
> >> bitmap_free(guc->submission_state.guc_ids_bitmap);
> >> + fini_tlb_lookup(guc);
> >> guc->submission_initialized = false;
> >> }
> >> @@ -4624,6 +4683,154 @@ g2h_context_lookup(struct intel_guc *guc, u32
> >> ctx_id)
> >> return ce;
> >> }
> >> +static void wait_wake_outstanding_tlb_g2h(struct intel_guc *guc, u32
> >> seqno)
> >> +{
> >> + struct intel_guc_tlb_wait *wait;
> >> + unsigned long flags;
> >> +
> >> + xa_lock_irqsave(&guc->tlb_lookup, flags);
> >> + wait = xa_load(&guc->tlb_lookup, seqno);
> >> +
> >> + /* We received a response after the waiting task did exit with a
> >> timeout */
> >> + if (wait)
> >> + wake_up(&wait->wq);
> >> + else
> >> + drm_dbg(&guc_to_gt(guc)->i915->drm,
> >> + "Stale TLB invalidation response with seqno %d\n", seqno);
> >> +
> >> + xa_unlock_irqrestore(&guc->tlb_lookup, flags);
> >> +}
> >> +
> >> +int intel_guc_tlb_invalidation_done(struct intel_guc *guc, const u32
> >> *hxg, u32 size)
> >> +{
> >> + u32 seqno, hxg_len, len;
> >> +
> >> + hxg_len = size - GUC_CTB_MSG_MIN_LEN;
> >> + len = hxg_len - GUC_HXG_MSG_MIN_LEN;
> >> +
> >> + /* Check for underflow */
> >> + if (unlikely(len < 1 || len > size))
> >> + return -EPROTO;
> >> +
> >> + seqno = hxg[GUC_HXG_MSG_MIN_LEN];
> >> + wait_wake_outstanding_tlb_g2h(guc, seqno);
> >> + return 0;
> >> +}
> >
> > For this we said multiple times it does not need to repeat the hxg_len,
> > len and all that ct_process_request already does if the passed in
> > parameter is appropriately adjusted.
> >
> >> +
> >> +static long must_wait_woken(struct wait_queue_entry *wq_entry, long
> >> timeout)
> >> +{
> >> + /*
> >> + * This is equivalent to wait_woken() with the exception that
> >> + * we do not wake up early if the kthread task has been completed.
> >> + * As we are called from page reclaim in any task context,
> >> + * we may be invoked from stopped kthreads, but we *must*
> >> + * complete the wait from the HW .
> >> + *
> >> + * A second problem is that since we are called under reclaim
> >> + * and wait_woken() inspected the thread state, it makes an invalid
> >> + * assumption that all PF_KTHREAD tasks have set_kthread_struct()
> >> + * called upon them, and will trigger a GPF in
> >> is_kthread_should_stop().
> >> + */
> >> + do {
> >> + set_current_state(TASK_UNINTERRUPTIBLE);
> >> + if (wq_entry->flags & WQ_FLAG_WOKEN)
> >> + break;
> >> +
> >> + timeout = schedule_timeout(timeout);
> >> + } while (timeout);
> >> + __set_current_state(TASK_RUNNING);
> >> +
> >> + /* See wait_woken() and woken_wake_function() */
> >> + smp_store_mb(wq_entry->flags, wq_entry->flags & ~WQ_FLAG_WOKEN);
> >> +
> >> + return timeout;
> >> +}
> >> +
> >> +static int guc_send_invalidate_tlb(struct intel_guc *guc, u32 type)
> >
> > New comment:
> >
> > u32 type should be enum intel_guc_tlb_inval_mode.
> >
> >> +{
> >> + struct intel_guc_tlb_wait _wq, *wq = &_wq;
> >> + DEFINE_WAIT_FUNC(wait, woken_wake_function);
> >> + struct intel_gt *gt = guc_to_gt(guc);
> >> + int err;
> >> + u32 seqno;
> >> + u32 action[] = {
> >> + INTEL_GUC_ACTION_TLB_INVALIDATION,
> >> + 0,
> >> + REG_FIELD_PREP(INTEL_GUC_TLB_INVAL_TYPE_MASK, type) |
> >> + REG_FIELD_PREP(INTEL_GUC_TLB_INVAL_MODE_MASK,
> >> + INTEL_GUC_TLB_INVAL_MODE_HEAVY) |
> >> + INTEL_GUC_TLB_INVAL_FLUSH_CACHE,
> >> + };
> >> + u32 size = ARRAY_SIZE(action);
> >> +
> >> + if (!intel_guc_ct_enabled(&guc->ct))
> >> + return -EINVAL;
> >
> > Here I asked what is the point of this guard since the callers already
> > have intel_guc_is_ready() checks. If there are concerns about races then
> > just one check at the entry to the function can't be enough, no?
> >
> >> +
> >> + init_waitqueue_head(&_wq.wq);
> >> +
> >> + if (xa_alloc_cyclic_irq(&guc->tlb_lookup, &seqno, wq,
> >> + xa_limit_32b, &guc->next_seqno,
> >> + GFP_ATOMIC | __GFP_NOWARN) < 0) {
> >> + /* Under severe memory pressure? Serialise TLB allocations */
> >> + xa_lock_irq(&guc->tlb_lookup);
> >> + wq = xa_load(&guc->tlb_lookup, guc->serial_slot);
> >> + wait_event_lock_irq(wq->wq,
> >> + !READ_ONCE(wq->busy),
> >> + guc->tlb_lookup.xa_lock);
> >> + /*
> >> + * Update wq->busy under lock to ensure only one waiter can
> >> + * issue the TLB invalidation command using the serial slot at a
> >> + * time. The condition is set to true before releasing the lock
> >> + * so that other caller continue to wait until woken up again.
> >> + */
> >> + wq->busy = true;
> >> + xa_unlock_irq(&guc->tlb_lookup);
> >> +
> >> + seqno = guc->serial_slot;
> >> + }
> >> +
> >> + action[1] = seqno;
> >> +
> >> + add_wait_queue(&wq->wq, &wait);
> >> +
> >> + err = intel_guc_send_busy_loop(guc, action, size,
> >> G2H_LEN_DW_INVALIDATE_TLB, true);
> >
> > Here I asked if we don't have a non-busy looping CT send helper, given
> > how this function is allowed to sleep would be nicer not to burn the CPU.
> >
> >> + if (err)
> >> + goto out;
> >> +
> >> + /*
> >> + * GuC has a timeout of 1ms for a TLB invalidation response from
> >> GAM. On a
> >> + * timeout GuC drops the request and has no mechanism to notify
> >> the host about
> >> + * the timeout. There is also no mechanism for determining the
> >> number of
> >> + * outstanding requests in the CT buffer. Ergo, keep a larger
> >> timeout that accounts
> >> + * for this individual timeout and the max number of outstanding
> >> requests that
> >> + * can be queued in CT buffer.
> >> + */
> >> +#define OUTSTANDING_GUC_TIMEOUT_PERIOD (HZ * 2)
> >
> > The updated comment addresses my feedback but I believe John had a
> > better suggestion on top.
> >
> >> + if (!must_wait_woken(&wait, OUTSTANDING_GUC_TIMEOUT_PERIOD)) {
> >> + gt_err(gt,
> >> + "TLB invalidation response timed out for seqno %u\n",
> >> seqno);
> >> + err = -ETIME;
> >> + }
> >> +out:
> >> + remove_wait_queue(&wq->wq, &wait);
> >> + if (seqno != guc->serial_slot)
> >> + xa_erase_irq(&guc->tlb_lookup, seqno);
> >> +
> >> + return err;
> >> +}
> >> +
> >> +/* Full TLB invalidation */
> >> +int intel_guc_invalidate_tlb_full(struct intel_guc *guc)
> >> +{
> >> + return guc_send_invalidate_tlb(guc, INTEL_GUC_TLB_INVAL_FULL);
> >> +}
> >> +
> >> +/* GuC TLB Invalidation: Invalidate the TLB's of GuC itself. */
> >> +int intel_guc_invalidate_tlb(struct intel_guc *guc)
> >> +{
> >> + return guc_send_invalidate_tlb(guc, INTEL_GUC_TLB_INVAL_GUC);
> >> +}
> >> +
> >> int intel_guc_deregister_done_process_msg(struct intel_guc *guc,
> >> const u32 *msg,
> >> u32 len)
> >
> > Regards,
> >
> > Tvrtko
>
