kernel/linux.git/arch/x86/include/asm/cpu.h, branch v6.6.134

x86/bugs: Add a Transient Scheduler Attacks mitigation

2025-07-10T14:03:21+00:00

Commit d8010d4ba43e9f790925375a7de100604a5e2dba upstream. Add the required features detection glue to bugs.c et all in order to support the TSA mitigation. Co-developed-by: Kim Phillips Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Pawan Gupta Signed-off-by: Greg Kroah-Hartman

x86/microcode/intel: Rework intel_find_matching_signature()

2025-03-07T15:45:51+00:00

commit b7fcd995b261c9976e05f47554529c98a0f1cbb0 upstream Take a cpu_signature argument and work from there. Move the match() helper next to the callsite as there is no point for having it in a header. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20231002115902.797820205@linutronix.de Signed-off-by: Greg Kroah-Hartman

x86/microcode/intel: Rework intel_cpu_collect_info()

2025-03-07T15:45:51+00:00

commit 164aa1ca537238c46923ccacd8995b4265aee47b upstream Nothing needs struct ucode_cpu_info. Make it take struct cpu_signature, let it return a boolean and simplify the implementation. Rename it now that the silly name clash with collect_cpu_info() is gone. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20231017211722.851573238@linutronix.de Signed-off-by: Greg Kroah-Hartman

cpu-hotplug: Provide prototypes for arch CPU registration

2023-10-11T12:27:37+00:00

Provide common prototypes for arch_register_cpu() and arch_unregister_cpu(). These are called by acpi_processor.c, with weak versions, so the prototype for this is already set. It is generally not necessary for function prototypes to be conditional on preprocessor macros. Some architectures (e.g. Loongarch) are missing the prototype for this, and rather than add it to Loongarch's asm/cpu.h, do the job once for everyone. Since this covers everyone, remove the now unnecessary prototypes in asm/cpu.h, and therefore remove the 'static' from one of ia64's arch_register_cpu() definitions. [ tglx: Bring back the ia64 part and remove the ACPI prototypes ] Signed-off-by: Russell King (Oracle) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/E1qkoRr-0088Q8-Da@rmk-PC.armlinux.org.uk

Merge tag 'x86-core-2023-06-26' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-06-26T21:45:53+00:00

Pull x86 core updates from Thomas Gleixner: "A set of fixes for kexec(), reboot and shutdown issues: - Ensure that the WBINVD in stop_this_cpu() has been completed before the control CPU proceedes. stop_this_cpu() is used for kexec(), reboot and shutdown to park the APs in a HLT loop. The control CPU sends an IPI to the APs and waits for their CPU online bits to be cleared. Once they all are marked "offline" it proceeds. But stop_this_cpu() clears the CPU online bit before issuing WBINVD, which means there is no guarantee that the AP has reached the HLT loop. This was reported to cause intermittent reboot/shutdown failures due to some dubious interaction with the firmware. This is not only a problem of WBINVD. The code to actually "stop" the CPU which runs between clearing the online bit and reaching the HLT loop can cause large enough delays on its own (think virtualization). That's especially dangerous for kexec() as kexec() expects that all APs are in a safe state and not executing code while the boot CPU jumps to the new kernel. There are more issues vs kexec() which are addressed separately. Cure this by implementing an explicit synchronization point right before the AP reaches HLT. This guarantees that the AP has completed the full stop proceedure. - Fix the condition for WBINVD in stop_this_cpu(). The WBINVD in stop_this_cpu() is required for ensuring that when switching to or from memory encryption no dirty data is left in the cache lines which might cause a write back in the wrong more later. This checks CPUID directly because the feature bit might have been cleared due to a command line option. But that CPUID check accesses leaf 0x8000001f::EAX unconditionally. Intel CPUs return the content of the highest supported leaf when a non-existing leaf is read, while AMD CPUs return all zeros for unsupported leafs. So the result of the test on Intel CPUs is lottery and on AMD its just correct by chance. While harmless it's incorrect and causes the conditional wbinvd() to be issued where not required, which caused the above issue to be unearthed. - Make kexec() robust against AP code execution Ashok observed triple faults when doing kexec() on a system which had been booted with "nosmt". It turned out that the SMT siblings which had been brought up partially are parked in mwait_play_dead() to enable power savings. mwait_play_dead() is monitoring the thread flags of the AP's idle task, which has been chosen as it's unlikely to be written to. But kexec() can overwrite the previous kernel text and data including page tables etc. When it overwrites the cache lines monitored by an AP that AP resumes execution after the MWAIT on eventually overwritten text, stack and page tables, which obviously might end up in a triple fault easily. Make this more robust in several steps: 1) Use an explicit per CPU cache line for monitoring. 2) Write a command to these cache lines to kick APs out of MWAIT before proceeding with kexec(), shutdown or reboot. The APs confirm the wakeup by writing status back and then enter a HLT loop. 3) If the system uses INIT/INIT/STARTUP for AP bringup, park the APs in INIT state. HLT is not a guarantee that an AP won't wake up and resume execution. HLT is woken up by NMI and SMI. SMI puts the CPU back into HLT (+/- firmware bugs), but NMI is delivered to the CPU which executes the NMI handler. Same issue as the MWAIT scenario described above. Sending an INIT/INIT sequence to the APs puts them into wait for STARTUP state, which is safe against NMI. There is still an issue remaining which can't be fixed: #MCE If the AP sits in HLT and receives a broadcast #MCE it will try to handle it with the obvious consequences. INIT/INIT clears CR4.MCE in the AP which will cause a broadcast #MCE to shut down the machine. So there is a choice between fire (HLT) and frying pan (INIT). Frying pan has been chosen as it's at least preventing the NMI issue. On systems which are not using INIT/INIT/STARTUP there is not much which can be done right now, but at least the obvious and easy to trigger MWAIT issue has been addressed" * tag 'x86-core-2023-06-26' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/smp: Put CPUs into INIT on shutdown if possible x86/smp: Split sending INIT IPI out into a helper function x86/smp: Cure kexec() vs. mwait_play_dead() breakage x86/smp: Use dedicated cache-line for mwait_play_dead() x86/smp: Remove pointless wmb()s from native_stop_other_cpus() x86/smp: Dont access non-existing CPUID leaf x86/smp: Make stop_other_cpus() more robust

x86/smp: Make stop_other_cpus() more robust

2023-06-20T12:51:46+00:00

Tony reported intermittent lockups on poweroff. His analysis identified the wbinvd() in stop_this_cpu() as the culprit. This was added to ensure that on SME enabled machines a kexec() does not leave any stale data in the caches when switching from encrypted to non-encrypted mode or vice versa. That wbinvd() is conditional on the SME feature bit which is read directly from CPUID. But that readout does not check whether the CPUID leaf is available or not. If it's not available the CPU will return the value of the highest supported leaf instead. Depending on the content the "SME" bit might be set or not. That's incorrect but harmless. Making the CPUID readout conditional makes the observed hangs go away, but it does not fix the underlying problem: CPU0 CPU1 stop_other_cpus() send_IPIs(REBOOT); stop_this_cpu() while (num_online_cpus() > 1); set_online(false); proceed... -> hang wbinvd() WBINVD is an expensive operation and if multiple CPUs issue it at the same time the resulting delays are even larger. But CPU0 already observed num_online_cpus() going down to 1 and proceeds which causes the system to hang. This issue exists independent of WBINVD, but the delays caused by WBINVD make it more prominent. Make this more robust by adding a cpumask which is initialized to the online CPU mask before sending the IPIs and CPUs clear their bit in stop_this_cpu() after the WBINVD completed. Check for that cpumask to become empty in stop_other_cpus() instead of watching num_online_cpus(). The cpumask cannot plug all holes either, but it's better than a raw counter and allows to restrict the NMI fallback IPI to be sent only the CPUs which have not reported within the timeout window. Fixes: 08f253ec3767 ("x86/cpu: Clear SME feature flag when not in use") Reported-by: Tony Battersby Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Ashok Raj Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com Link: https://lore.kernel.org/r/87h6r770bv.ffs@tglx

x86/topology: Remove CPU0 hotplug option

2023-05-15T11:44:49+00:00

This was introduced together with commit e1c467e69040 ("x86, hotplug: Wake up CPU0 via NMI instead of INIT, SIPI, SIPI") to eventually support physical hotplug of CPU0: "We'll change this code in the future to wake up hard offlined CPU0 if real platform and request are available." 11 years later this has not happened and physical hotplug is not officially supported. Remove the cruft. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Kelley Tested-by: Oleksandr Natalenko Tested-by: Helge Deller # parisc Tested-by: Guilherme G. Piccoli # Steam Deck Link: https://lore.kernel.org/r/20230512205255.715707999@linutronix.de

x86/smpboot: Rename start_cpu0() to soft_restart_cpu()

2023-05-15T11:44:48+00:00

This is used in the SEV play_dead() implementation to re-online CPUs. But that has nothing to do with CPU0. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Kelley Tested-by: Oleksandr Natalenko Tested-by: Helge Deller # parisc Tested-by: Guilherme G. Piccoli # Steam Deck Link: https://lore.kernel.org/r/20230512205255.662319599@linutronix.de

x86/microcode/intel: Add hdr_type to intel_microcode_sanity_check()

2022-11-18T21:08:19+00:00

IFS test images and microcode blobs use the same header format. Microcode blobs use header type of 1, whereas IFS test images will use header type of 2. In preparation for IFS reusing intel_microcode_sanity_check(), add header type as a parameter for sanity check. [ bp: Touchups. ] Signed-off-by: Jithu Joseph Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Reviewed-by: Ashok Raj Link: https://lore.kernel.org/r/20221117035935.4136738-9-jithu.joseph@intel.com

x86/microcode/intel: Reuse microcode_sanity_check()

2022-11-18T21:00:17+00:00

IFS test image carries the same microcode header as regular Intel microcode blobs. Reuse microcode_sanity_check() in the IFS driver to perform sanity check of the IFS test images too. Signed-off-by: Jithu Joseph Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Reviewed-by: Ashok Raj Reviewed-by: Sohil Mehta Link: https://lore.kernel.org/r/20221117035935.4136738-8-jithu.joseph@intel.com