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Box" To: hansg@kernel.org, ilpo.jarvinen@linux.intel.com, irenic.rajneesh@gmail.com Cc: "David E. Box" , linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org, srinivas.pandruvada@linux.intel.com, xi.pardee@linux.intel.com Subject: [PATCH v8 05/15] platform/x86/intel/pmt: Cache the telemetry discovery header Date: Fri, 12 Jun 2026 14:01:46 -0700 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: 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 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 =3D 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 --- V8 - No changes V7 changes: - Replaced min_t(size_t, ...) with min() because both operands are size_t (Ilpo). 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 =3D 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 | 11 +++++++++++ drivers/platform/x86/intel/pmt/class.h | 1 + drivers/platform/x86/intel/pmt/telemetry.c | 12 ++++++------ 3 files changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/= intel/pmt/class.c index 7da8279b54f8..8d27f59d5bff 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 +384,16 @@ 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); =20 + /* + * 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(sizeof(entry->disc_header), resource_size(disc_res))); + if (ns->pmt_pre_decode) { ret =3D 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 *de= v, u32 guid, u32 type) static int pmt_telem_header_decode(struct intel_pmt_entry *entry, struct device *dev) { - void __iomem *disc_table =3D entry->disc_table; struct intel_pmt_header *header =3D &entry->header; + u32 *disc_header =3D entry->disc_header; =20 - header->access_type =3D TELEM_ACCESS(readl(disc_table)); - header->guid =3D readl(disc_table + TELEM_GUID_OFFSET); - header->base_offset =3D readl(disc_table + TELEM_BASE_OFFSET); + header->access_type =3D TELEM_ACCESS(disc_header[0]); + header->guid =3D disc_header[1]; + header->base_offset =3D disc_header[2]; =20 /* Size is measured in DWORDS, but accessor returns bytes */ - header->size =3D TELEM_SIZE(readl(disc_table)); - header->telem_type =3D TELEM_TYPE(readl(entry->disc_table)); + header->size =3D TELEM_SIZE(disc_header[0]); + header->telem_type =3D TELEM_TYPE(disc_header[0]); =20 return 0; } --=20 2.43.0