From nobody Sat Nov 30 12:31:50 2024 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28B1D176259; Mon, 9 Sep 2024 13:18:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725887924; cv=none; b=gGatsHpyyMMtjbZtprzCIhN3AKh9f7jdntSbC5aRiHaaHmA+QdCj99W17ho51P7WRWbsSMrSguwrst5VxJR4tcKDMrovw9nXJ8GiqPNWjTk7yCzsqBd29y2v5v5BeA/EufJTJx+IihjPdbq5FvCmx+t6rDPJ+/n/LMN2l+sCDCA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725887924; c=relaxed/simple; bh=LaS630GWSJUP5/OlzQClgenx4KF+6YVTc43cjcpFnEE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ozO4k5lW6yhtQ/RRyi3KcCLO3y5AGGgpCMrRBsDqyUQ2Bfi9ujCvFe/nNmIieMwcy2ZFdz8P7clNnM+B9bcVoVhbAFXbLCWRXp/nVfECd9AJVNSp7rvn4aAv6HBnIqPdA2n++M4oUhQbdrhyPoDMoCv9XT6gOZYwOVXo7aHBNcU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=nvydEuWP; arc=none smtp.client-ip=198.175.65.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="nvydEuWP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1725887922; x=1757423922; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=LaS630GWSJUP5/OlzQClgenx4KF+6YVTc43cjcpFnEE=; b=nvydEuWPzPtP7vERkOJV/Fzjzpm429tssi/gsHmRD54obWQgs6wS5/VA XNnY1lTrCHUTsR3+Dm3kJllD8AWIMMSe8tlI5U+/zJpw7K65qmj+uQMB3 By3vAfkimRPr3v/Rzl20tjWImQ70HWg1+IroGOrOxm1v4XjBpJeHaB/sr tIC34E0zibfypV6reclcjkV6jjjeGoCAt3TNM70uEKvSZ0EwtAov3M9nw n7IHllIEuoIw3ZDEry1Hk1dKHrjMalu4+Ay9dEPVjHXcxEe9G9rV7dXss 2DeORF1G4BYxRRLgc+YdfNZBL1Irlhlf1r93C60F6xErm8Uy3OxIV9EHy A==; X-CSE-ConnectionGUID: 0bjkHbjZRayxlKZ9aP3oUw== X-CSE-MsgGUID: 9lhC6qTbQfWwtrP8dR20RQ== X-IronPort-AV: E=McAfee;i="6700,10204,11190"; a="28363546" X-IronPort-AV: E=Sophos;i="6.10,214,1719903600"; d="scan'208";a="28363546" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2024 06:18:41 -0700 X-CSE-ConnectionGUID: y9IAZPafTayJLBL4nz5pOw== X-CSE-MsgGUID: 0VC8m7WDSiqzEP0MrMRAvQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,214,1719903600"; d="scan'208";a="104127985" Received: from yzhao56-desk.sh.intel.com ([10.239.159.62]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2024 06:18:37 -0700 From: Yan Zhao To: kraxel@redhat.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, daniel@ffwll.ch, virtualization@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: pbonzini@redhat.com, seanjc@google.com, kvm@vger.kernel.org, Yan Zhao , Vitaly Kuznetsov , Kevin Tian Subject: [PATCH v2] drm/bochs: use devm_ioremap_wc() to map framebuffer Date: Mon, 9 Sep 2024 21:16:43 +0800 Message-ID: <20240909131643.28915-1-yan.y.zhao@intel.com> X-Mailer: git-send-email 2.43.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Opt for devm_ioremap_wc() over devm_ioremap() when mapping the framebuffer. Using devm_ioremap() results in the VA being mapped with PAT=3DUC-, which considerably slows down drm_fb_memcpy(). In contrast, devm_ioremap_wc() maps the VA with PAT set to WC, leading to better performance on platforms where access to UC memory is much slower than WC memory. Here's the performance data measured in a guest on the physical machine "Sapphire Rapids XCC". With host KVM honors guest PAT memory types, the effective memory type for this framebuffer range is - WC when devm_ioremap_wc() is used - UC- when devm_ioremap() is used. The data presented is an average from 10 execution runs. Cycles: Avg cycles of executed bochs_primary_plane_helper_atomic_update() from VM boot to GDM show up Cnt: Avg cnt of executed bochs_primary_plane_helper_atomic_update() from VM boot to GDM show up T: Avg time of each bochs_primary_plane_helper_atomic_update(). ------------------------------------------------- | | devm_ioremap() | devm_ioremap_wc() | |------------|----------------|-------------------| | Cycles | 211.545M | 0.157M | |------------|----------------|-------------------| | Cnt | 142 | 1917 | |------------|----------------|-------------------| | T | 0.1748s | 0.0004s | ------------------------------------------------- Note: Following the rebase to [3], the previously reported GDM failure on the VGA device [1] can no longer be reproduced, thanks to the memory management improvements made in [2]. Despite this, I have proceeded to submit this patch because of the noticeable performance improvements it provides. Reported-by: Vitaly Kuznetsov Closes: https://lore.kernel.org/all/87jzfutmfc.fsf@redhat.com/#t Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Kevin Tian Cc: Thomas Zimmermann Signed-off-by: Yan Zhao Link: https://lore.kernel.org/all/87jzfutmfc.fsf@redhat.com/#t [1] Link: https://patchwork.freedesktop.org/series/138086 [2] Link: https://gitlab.freedesktop.org/drm/misc/kernel/-/tree/drm-misc-next [= 3] Reviewed-by: Thomas Zimmermann Tested-by: Thomas Zimmermann Tested-by: Vitaly Kuznetsov --- v2: - Rebased to the latest drm-misc-next branch. [2] - Updated patch log to match the base code. v1: https://lore.kernel.org/all/20240909051529.26776-1-yan.y.zhao@intel.com --- drivers/gpu/drm/tiny/bochs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c index 69c5f65e9853..9055b1dd66df 100644 --- a/drivers/gpu/drm/tiny/bochs.c +++ b/drivers/gpu/drm/tiny/bochs.c @@ -268,7 +268,7 @@ static int bochs_hw_init(struct bochs_device *bochs) if (!devm_request_mem_region(&pdev->dev, addr, size, "bochs-drm")) DRM_WARN("Cannot request framebuffer, boot fb still active?\n"); =20 - bochs->fb_map =3D devm_ioremap(&pdev->dev, addr, size); + bochs->fb_map =3D devm_ioremap_wc(&pdev->dev, addr, size); if (bochs->fb_map =3D=3D NULL) { DRM_ERROR("Cannot map framebuffer\n"); return -ENOMEM; --=20 2.43.2