From patchwork Thu Jun 11 16:05:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11600359 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D4B0814E3 for ; Thu, 11 Jun 2020 16:06:18 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B10BE206DC for ; Thu, 11 Jun 2020 16:06:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B10BE206DC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A0D216E83F; Thu, 11 Jun 2020 16:06:16 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6B0686E83F for ; Thu, 11 Jun 2020 16:06:15 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from build.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 21467001-1500050 for multiple; Thu, 11 Jun 2020 17:05:32 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Thu, 11 Jun 2020 17:05:29 +0100 Message-Id: <20200611160529.9558-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drm/i915/gt: Flush gen3 relocs harder, again X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" gen3 does not fully flush MI stores to memory on MI_FLUSH, such that a subsequent read from e.g. the sampler can bypass the store and read the stale value from memory. This is a serious issue when we are using MI stores to rewrite the batches for relocation, as it means that the batch is reading from random user/kernel memory. While it is particularly sensitive [and detectable] for relocations, reading stale data at any time is a worry. Having started with a small number of delaying stores and doubling until no more incoherency was seen over a few hours (with and without background memory pressure), 32 was the magic number. Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2018 References: a889580c087a ("drm/i915: Flush GPU relocs harder for gen3") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Joonas Lahtinen --- So gen3 requires a delay after to flush the previous stores, gen5 is assuming it requires a delay between the seqno and the MI_USER_INTERRUPT. Here I've made gen5 reuse the gen3 approach, but I need to verify that it still holds. --- drivers/gpu/drm/i915/gt/gen2_engine_cs.c | 39 +++++++++--------------- 1 file changed, 15 insertions(+), 24 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/gen2_engine_cs.c b/drivers/gpu/drm/i915/gt/gen2_engine_cs.c index 3fb0dc1fb910..342c476ec872 100644 --- a/drivers/gpu/drm/i915/gt/gen2_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/gen2_engine_cs.c @@ -142,19 +142,26 @@ int gen4_emit_flush_vcs(struct i915_request *rq, u32 mode) return 0; } -u32 *gen3_emit_breadcrumb(struct i915_request *rq, u32 *cs) +static u32 *__gen2_emit_breadcrumb(struct i915_request *rq, u32 *cs, int count) { GEM_BUG_ON(i915_request_active_timeline(rq)->hwsp_ggtt != rq->engine->status_page.vma); GEM_BUG_ON(offset_in_page(i915_request_active_timeline(rq)->hwsp_offset) != I915_GEM_HWS_SEQNO_ADDR); *cs++ = MI_FLUSH; + *cs++ = MI_NOOP; + + while (count--) { + *cs++ = MI_STORE_DWORD_INDEX; + *cs++ = I915_GEM_HWS_SCRATCH * sizeof(u32); + *cs++ = rq->fence.seqno; + *cs++ = MI_FLUSH | MI_NO_WRITE_FLUSH; + } *cs++ = MI_STORE_DWORD_INDEX; *cs++ = I915_GEM_HWS_SEQNO_ADDR; *cs++ = rq->fence.seqno; *cs++ = MI_USER_INTERRUPT; - *cs++ = MI_NOOP; rq->tail = intel_ring_offset(rq, cs); assert_ring_tail_valid(rq->ring, rq->tail); @@ -162,31 +169,15 @@ u32 *gen3_emit_breadcrumb(struct i915_request *rq, u32 *cs) return cs; } -#define GEN5_WA_STORES 8 /* must be at least 1! */ -u32 *gen5_emit_breadcrumb(struct i915_request *rq, u32 *cs) +u32 *gen3_emit_breadcrumb(struct i915_request *rq, u32 *cs) { - int i; - - GEM_BUG_ON(i915_request_active_timeline(rq)->hwsp_ggtt != rq->engine->status_page.vma); - GEM_BUG_ON(offset_in_page(i915_request_active_timeline(rq)->hwsp_offset) != I915_GEM_HWS_SEQNO_ADDR); - - *cs++ = MI_FLUSH; - - BUILD_BUG_ON(GEN5_WA_STORES < 1); - for (i = 0; i < GEN5_WA_STORES; i++) { - *cs++ = MI_STORE_DWORD_INDEX; - *cs++ = I915_GEM_HWS_SEQNO_ADDR; - *cs++ = rq->fence.seqno; - } - - *cs++ = MI_USER_INTERRUPT; - - rq->tail = intel_ring_offset(rq, cs); - assert_ring_tail_valid(rq->ring, rq->tail); + return __gen2_emit_breadcrumb(rq, cs, 32); +} - return cs; +u32 *gen5_emit_breadcrumb(struct i915_request *rq, u32 *cs) +{ + return __gen2_emit_breadcrumb(rq, cs, 8); } -#undef GEN5_WA_STORES /* Just userspace ABI convention to limit the wa batch bo to a resonable size */ #define I830_BATCH_LIMIT SZ_256K