talos-obmc-linux/arch/arm/include, branch dev-5.0

ARM: avoid Cortex-A9 livelock on tight dmb loops

2019-04-05T20:34:45+00:00

[ Upstream commit 5388a5b82199facacd3d7ac0d05aca6e8f902fed ] machine_crash_nonpanic_core() does this: while (1) cpu_relax(); because the kernel has crashed, and we have no known safe way to deal with the CPU. So, we place the CPU into an infinite loop which we expect it to never exit - at least not until the system as a whole is reset by some method. In the absence of erratum 754327, this code assembles to: b . In other words, an infinite loop. When erratum 754327 is enabled, this becomes: 1: dmb b 1b It has been observed that on some systems (eg, OMAP4) where, if a crash is triggered, the system tries to kexec into the panic kernel, but fails after taking the secondary CPU down - placing it into one of these loops. This causes the system to livelock, and the most noticable effect is the system stops after issuing: Loading crashdump kernel... to the system console. The tested as working solution I came up with was to add wfe() to these infinite loops thusly: while (1) { cpu_relax(); wfe(); } which, without 754327 builds to: 1: wfe b 1b or with 754327 is enabled: 1: dmb wfe b 1b Adding "wfe" does two things depending on the environment we're running under: - where we're running on bare metal, and the processor implements "wfe", it stops us spinning endlessly in a loop where we're never going to do any useful work. - if we're running in a VM, it allows the CPU to be given back to the hypervisor and rescheduled for other purposes (maybe a different VM) rather than wasting CPU cycles inside a crashed VM. However, in light of erratum 794072, Will Deacon wanted to see 10 nops as well - which is reasonable to cover the case where we have erratum 754327 enabled _and_ we have a processor that doesn't implement the wfe hint. So, we now end up with: 1: wfe b 1b when erratum 754327 is disabled, or: 1: dmb nop nop nop nop nop nop nop nop nop nop wfe b 1b when erratum 754327 is enabled. We also get the dmb + 10 nop sequence elsewhere in the kernel, in terminating loops. This is reasonable - it means we get the workaround for erratum 794072 when erratum 754327 is enabled, but still relinquish the dead processor - either by placing it in a lower power mode when wfe is implemented as such or by returning it to the hypervisior, or in the case where wfe is a no-op, we use the workaround specified in erratum 794072 to avoid the problem. These as two entirely orthogonal problems - the 10 nops addresses erratum 794072, and the wfe is an optimisation that makes the system more efficient when crashed either in terms of power consumption or by allowing the host/other VMs to make use of the CPU. I don't see any reason not to use kexec() inside a VM - it has the potential to provide automated recovery from a failure of the VMs kernel with the opportunity for saving a crashdump of the failure. A panic() with a reboot timeout won't do that, and reading the libvirt documentation, setting on_reboot to "preserve" won't either (the documentation states "The preserve action for an on_reboot event is treated as a destroy".) Surely it has to be a good thing to avoiding having CPUs spinning inside a VM that is doing no useful work. Acked-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Sasha Levin

ARM: 8830/1: NOMMU: Toggle only bits in EXC_RETURN we are really care of

2019-04-05T20:34:45+00:00

[ Upstream commit 72cd4064fccaae15ab84d40d4be23667402df4ed ] ARMv8M introduces support for Security extension to M class, among other things it affects exception handling, especially, encoding of EXC_RETURN. The new bits have been added: Bit [6] Secure or Non-secure stack Bit [5] Default callee register stacking Bit [0] Exception Secure which conflicts with hard-coded value of EXC_RETURN: In fact, we only care of few bits: Bit [3] Mode (0 - Handler, 1 - Thread) Bit [2] Stack pointer selection (0 - Main, 1 - Process) We can toggle only those bits and left other bits as they were on exception entry. It is basically, what patch does - saves EXC_RETURN when we do transition form Thread to Handler mode (it is first svc), so later saved value is used instead of EXC_RET_THREADMODE_PROCESSSTACK. Signed-off-by: Vladimir Murzin Signed-off-by: Russell King Signed-off-by: Sasha Levin

Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm

2019-02-18T17:59:28+00:00

Pull ARM fixes from Russell King: "A few ARM fixes: - Dietmar Eggemann noticed an issue with IRQ migration during CPU hotplug stress testing. - Mathieu Desnoyers noticed that a previous fix broke optimised kprobes. - Robin Murphy noticed a case where we were not clearing the dma_ops" * tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: ARM: 8835/1: dma-mapping: Clear DMA ops on teardown ARM: 8834/1: Fix: kprobes: optimized kprobes illegal instruction ARM: 8824/1: fix a migrating irq bug when hotplug cpu

Merge tag 'kvm-arm-fixes-for-5.0' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-master

2019-02-13T18:39:24+00:00

KVM/ARM fixes for 5.0: - Fix the way we reset vcpus, plugging the race that could happen on VHE - Fix potentially inconsistent group setting for private interrupts - Don't generate UNDEF when LORegion feature is present - Relax the restriction on using stage2 PUD huge mapping - Turn some spinlocks into raw_spinlocks to help RT compliance

arm: KVM: Add missing kvm_stage2_has_pmd() helper

2019-02-07T11:44:47+00:00

Fixup 32bit by providing the now required helper. Cc: Suzuki Poulose Signed-off-by: Marc Zyngier

arm/arm64: KVM: Allow a VCPU to fully reset itself

2019-02-07T11:44:13+00:00

The current kvm_psci_vcpu_on implementation will directly try to manipulate the state of the VCPU to reset it. However, since this is not done on the thread that runs the VCPU, we can end up in a strangely corrupted state when the source and target VCPUs are running at the same time. Fix this by factoring out all reset logic from the PSCI implementation and forwarding the required information along with a request to the target VCPU. Reviewed-by: Andrew Jones Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall

ARM: 8824/1: fix a migrating irq bug when hotplug cpu

2019-02-01T21:54:49+00:00

Arm TC2 fails cpu hotplug stress test. This issue was tracked down to a missing copy of the new affinity cpumask for the vexpress-spc interrupt into struct irq_common_data.affinity when the interrupt is migrated in migrate_one_irq(). Fix it by replacing the arm specific hotplug cpu migration with the generic irq code. This is the counterpart implementation to commit 217d453d473c ("arm64: fix a migrating irq bug when hotplug cpu"). Tested with cpu hotplug stress test on Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y). The vexpress-spc interrupt (irq=22) on this board is affine to CPU0. Its affinity cpumask now changes correctly e.g. from 0 to 1-4 when CPU0 is hotplugged out. Suggested-by: Marc Zyngier Signed-off-by: Dietmar Eggemann Acked-by: Marc Zyngier Reviewed-by: Linus Walleij Signed-off-by: Russell King

arm64/xen: fix xen-swiotlb cache flushing

2019-01-23T21:14:56+00:00

Xen-swiotlb hooks into the arm/arm64 arch code through a copy of the DMA DMA mapping operations stored in the struct device arch data. Switching arm64 to use the direct calls for the merged DMA direct / swiotlb code broke this scheme. Replace the indirect calls with direct-calls in xen-swiotlb as well to fix this problem. Fixes: 356da6d0cde3 ("dma-mapping: bypass indirect calls for dma-direct") Reported-by: Julien Grall Signed-off-by: Christoph Hellwig Reviewed-by: Stefano Stabellini

arch: remove redundant UAPI generic-y defines

2019-01-06T01:22:15+00:00

Now that Kbuild automatically creates asm-generic wrappers for missing mandatory headers, it is redundant to list the same headers in generic-y and mandatory-y. Suggested-by: Sam Ravnborg Signed-off-by: Masahiro Yamada Acked-by: Sam Ravnborg

arch: remove stale comments "UAPI Header export list"

2019-01-06T00:46:51+00:00

These comments are leftovers of commit fcc8487d477a ("uapi: export all headers under uapi directories"). Prior to that commit, exported headers must be explicitly added to header-y. Now, all headers under the uapi/ directories are exported. Signed-off-by: Masahiro Yamada