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A self-describing mechanism for the uncore PerfMon hardware has been introduced with the latest Intel platforms. By reading through an MMIO page worth of information, perf can 'discover' all the standard uncore PerfMon registers in a machine. The discovery mechanism relies on BIOS's support. With a proper BIOS, a PCI device with the unique capability ID 0x23 can be found on each die. Perf can retrieve the information of all available uncore PerfMons from the device via MMIO. The information is composed of one global discovery table and several unit discovery tables. - The global discovery table includes global uncore information of the die, e.g., the address of the global control register, the offset of the global status register, the number of uncore units, the offset of unit discovery tables, etc. - The unit discovery table includes generic uncore unit information, e.g., the access type, the counter width, the address of counters, the address of the counter control, the unit ID, the unit type, etc. The unit is also called "box" in the code. Perf can provide basic uncore support based on this information with the following patches. To locate the PCI device with the discovery tables, check the generic PCI ID first. If it doesn't match, go through the entire PCI device tree and locate the device with the unique capability ID. The uncore information is similar among dies. To save parsing time and space, only completely parse and store the discovery tables on the first die and the first box of each die. The parsed information is stored in an RB tree structure, intel_uncore_discovery_type. The size of the stored discovery tables varies among platforms. It's around 4KB for a Sapphire Rapids server. If a BIOS doesn't support the 'discovery' mechanism, the uncore driver will exit with -ENODEV. There is nothing changed. Add a module parameter to disable the discovery feature. If a BIOS gets the discovery tables wrong, users can have an option to disable the feature. For the current patchset, the uncore driver will exit with -ENODEV. In the future, it may fall back to the hardcode uncore driver on a known platform. Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/1616003977-90612-2-git-send-email-kan.liang@linux.intel.com |
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