From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.11]) (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 65842312826; Wed, 10 Jun 2026 12:44:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781095492; cv=none; b=je8zfLJHsrTTY/P/Sc0/IP+kYvy/wR/RXf8gf8akOk5A/m0Cw+L/f4RIi3zkdGF9t6Sbt+6wmpi8gj0gPH1ySNGdVFYgQf4uWxQqXORQgL7HWrjAvvXdJP96e6sRYzzX5rTE02GNqVF/LwOhCLUvPBuKz7xJ8tX//in6NGtw/k4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781095492; c=relaxed/simple; bh=awaqJM2vkM2379GX8wlCePQaPeHMcu+BJu3pUenZ9Wo=; h=From:Date:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=nftnuFtsKsogIK1ym4KpSSYaz0CS3gE0rjgApEmvTeqFRFqdPmfjXXPRKn4/8tnhIch6ymbzvnA4nN+0VErJzIF9gIK6J/Ut5QJ8FkYdn6q8Ti8Zr7pejnfDwenWaeLY19J2cGcs3MQupxxxswPpHESb6Naq55W4AzBAe+RBvP0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=QlpH4j1W; arc=none smtp.client-ip=198.175.65.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="QlpH4j1W" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1781095492; x=1812631492; h=from:date:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=awaqJM2vkM2379GX8wlCePQaPeHMcu+BJu3pUenZ9Wo=; b=QlpH4j1W3rP4zNxNYybQY76tYlT49sxBRgENkxSUjYRriLw17NPu689C 7y94oh3cqdfJYEJGUoAqz99o8uwpJrUQag1GvSffETWLe4+bwv9mqpnoU XZOjXjrJj6cZbKIO6Q7KaarMaMlWHjyxlevZo0Egi1P5tvW3zMC5BUknu vsnwVj2qA9qz8aliLy+DQ20pemHqcTDUlog+Y+K+jmUxHQB1mmNKWlM58 YsVV9RTIK3C8Hiah3HMZmrdf1MqGuISbzjJeI/9HNhu96CC6b9HNbgTQ+ P+KPAJkTikczwk6SF4fcVQS/Wyv2PptdGDKpoCSyCq2Iv3DZW8RbFsFnh Q==; X-CSE-ConnectionGUID: YdH86aHZR0iTv7XxW0LqoQ== X-CSE-MsgGUID: 10JTSuYPSEy7JkvV2XwEwA== X-IronPort-AV: E=McAfee;i="6800,10657,11812"; a="92205680" X-IronPort-AV: E=Sophos;i="6.24,197,1774335600"; d="scan'208";a="92205680" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jun 2026 05:44:51 -0700 X-CSE-ConnectionGUID: m/Qod7NdRHmYQbTkuYqDbg== X-CSE-MsgGUID: wHDLezu+SJuhMt1/exKcYw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,197,1774335600"; d="scan'208";a="242024676" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.18]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jun 2026 05:44:48 -0700 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Wed, 10 Jun 2026 15:44:44 +0300 (EEST) To: "David E. Box" cc: Hans de Goede , irenic.rajneesh@gmail.com, LKML , platform-driver-x86@vger.kernel.org, srinivas.pandruvada@linux.intel.com, xi.pardee@linux.intel.com Subject: Re: [PATCH v6 05/15] platform/x86/intel/pmt: Cache the telemetry discovery header In-Reply-To: <6337062b826c4169eb48389ed581a4fe6085c409.1780248804.git.david.e.box@linux.intel.com> Message-ID: References: <6337062b826c4169eb48389ed581a4fe6085c409.1780248804.git.david.e.box@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Sun, 31 May 2026, David E. Box wrote: > pmt_telem_header_decode() only needs the discovery header dwords, but it > currently decodes them by reading directly from entry->disc_table. > > Cache the discovery header in intel_pmt_entry when the device is created > and have telemetry decode use the cached values instead of performing MMIO > reads at decode time. > > The DVSEC discovery resource for a namespace is sized by its per-entry > entry_size (in dwords), which can be less than the 4-dword cache (e.g. > telemetry uses entry_size = 3, i.e. 12 bytes). Cap the memcpy_fromio() > to resource_size(disc_res) so the new cache does not read past the > mapped region. Any unread dwords stay zero from the zero-initialized > allocation of the containing struct. > > This keeps the telemetry header decode path independent of how the > discovery data is backed and avoids baking a direct MMIO assumption into > the feature-specific decode logic. > > Assisted-by: GitHub-Copilot:claude-opus-4.7 > Signed-off-by: David E. Box > --- > V6 changes: > - Added #include for min_t() macro used in > memcpy_fromio() size calculation (Ilpo). > > V5 changes: > - Cap memcpy_fromio() of the cached discovery header to > resource_size(disc_res) so the newly introduced cache does not > over-read namespaces whose DVSEC entry_size is smaller than the > cache (e.g. telemetry has entry_size = 3, 12 bytes). > > V4 - No changes > > V3 changes: > - New patch split out from PMT header-fetch rework to cache discovery > header data before downstream decode/population. > - Added to carry the post-v3 bug fix while preserving the original series > ordering intent. > > drivers/platform/x86/intel/pmt/class.c | 12 ++++++++++++ > drivers/platform/x86/intel/pmt/class.h | 1 + > drivers/platform/x86/intel/pmt/telemetry.c | 12 ++++++------ > 3 files changed, 19 insertions(+), 6 deletions(-) > > diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c > index 7da8279b54f8..44a0a52014fc 100644 > --- a/drivers/platform/x86/intel/pmt/class.c > +++ b/drivers/platform/x86/intel/pmt/class.c > @@ -12,6 +12,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -383,6 +384,17 @@ int intel_pmt_dev_create(struct intel_pmt_entry *entry, struct intel_pmt_namespa > if (IS_ERR(entry->disc_table)) > return PTR_ERR(entry->disc_table); > > + /* > + * The mapped discovery resource may be smaller than disc_header (its > + * size is the namespace's DVSEC entry_size in dwords, which can be > + * less than 4). Cap the copy to the actual resource size to avoid > + * reading past the mapped region; any unread dwords stay zero from > + * the zero-initialized allocation of the containing struct. > + */ > + memcpy_fromio(entry->disc_header, entry->disc_table, > + min_t(size_t, sizeof(entry->disc_header), > + resource_size(disc_res))); I seem to have missed earlier that both of these are size_t already, so min() should suffice. > + > if (ns->pmt_pre_decode) { > ret = ns->pmt_pre_decode(intel_vsec_dev, entry); > if (ret) > diff --git a/drivers/platform/x86/intel/pmt/class.h b/drivers/platform/x86/intel/pmt/class.h > index 8a0db0ef58c1..84202fc7920c 100644 > --- a/drivers/platform/x86/intel/pmt/class.h > +++ b/drivers/platform/x86/intel/pmt/class.h > @@ -44,6 +44,7 @@ struct intel_pmt_entry { > struct telem_endpoint *ep; > struct pci_dev *pcidev; > struct intel_pmt_header header; > + u32 disc_header[4]; > struct bin_attribute pmt_bin_attr; > const struct attribute_group *attr_grp; > struct kobject *kobj; > diff --git a/drivers/platform/x86/intel/pmt/telemetry.c b/drivers/platform/x86/intel/pmt/telemetry.c > index d22f633638be..953f35b6daec 100644 > --- a/drivers/platform/x86/intel/pmt/telemetry.c > +++ b/drivers/platform/x86/intel/pmt/telemetry.c > @@ -72,16 +72,16 @@ static bool pmt_telem_region_overlaps(struct device *dev, u32 guid, u32 type) > static int pmt_telem_header_decode(struct intel_pmt_entry *entry, > struct device *dev) > { > - void __iomem *disc_table = entry->disc_table; > struct intel_pmt_header *header = &entry->header; > + u32 *disc_header = entry->disc_header; > > - header->access_type = TELEM_ACCESS(readl(disc_table)); > - header->guid = readl(disc_table + TELEM_GUID_OFFSET); > - header->base_offset = readl(disc_table + TELEM_BASE_OFFSET); > + header->access_type = TELEM_ACCESS(disc_header[0]); > + header->guid = disc_header[1]; > + header->base_offset = disc_header[2]; > > /* Size is measured in DWORDS, but accessor returns bytes */ > - header->size = TELEM_SIZE(readl(disc_table)); > - header->telem_type = TELEM_TYPE(readl(entry->disc_table)); > + header->size = TELEM_SIZE(disc_header[0]); > + header->telem_type = TELEM_TYPE(disc_header[0]); > > return 0; > } > -- i.