From: David E. Box Date: Fri, 12 Jun 2026 21:01:46 +0000 (-0700) Subject: platform/x86/intel/pmt: Cache the telemetry discovery header X-Git-Tag: v7.2-rc1~61^2~10 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4dfc7dca6e934ca414d8d3c70a84e79d13d9e750;p=thirdparty%2Fkernel%2Flinux.git platform/x86/intel/pmt: Cache the telemetry discovery header 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 Link: https://patch.msgid.link/f805e2ada52dc0661761cda7f692e76e6ea2d257.1781294741.git.david.e.box@linux.intel.com Reviewed-by: Ilpo Järvinen Signed-off-by: Ilpo Järvinen --- diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c index 7da8279b54f85..8d27f59d5bff0 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); + /* + * 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 = 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 8a0db0ef58c17..84202fc7920c9 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 d22f633638be7..953f35b6daecb 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; }