Messages in this thread | | | Date | Thu, 9 Nov 2017 09:52:29 -0600 (CST) | From | Manoj Iyer <> | Subject | Re: [3/3] arm64: Add software workaround for Falkor erratum 1041 |
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James,
(sorry for top-posting)
Applied patch 3 patches to Ubuntu Artful Kernel ( 4.13.0-16-generic )
- Start 20 VMs one at a time
In a loop: - Stop (virsh destroy) 20 VMs one at a time - Start (virsh start) 20 VMs one at a time.
The system reset's itself after starting the last VM on the 1st loop displaying the following:
awrep6 login: [ 603.349141] ACPI CPPC: PCC check channel failed. Status=0 [ 603.765101] ACPI CPPC: PCC check channel failed. Status=0 [ 603.937389] ACPI CPPC: PCC check channel failed. Status=0 [ 608.285495] ACPI CPPC: PCC check channel failed. Status=0 [ 608.289481] ACPI CPPC: PCC check channel failed. Status=0
SYS_DBG: Running SDI image (immediate mode) SYS_DBG: Ram Dump Init SYS_DBG: Failed to init SD card SYS_DBG: Resetting system!
Followed by the following messages on system reboot: [ 6.616891] BERT: Error records from previous boot: [ 6.621655] [Hardware Error]: event severity: fatal [ 6.626516] [Hardware Error]: imprecise tstamp: 0000-00-00 00:00:00 [ 6.632851] [Hardware Error]: Error 0, type: fatal [ 6.637713] [Hardware Error]: section type: unknown, d2e2621c-f936-468d-0d84-15a4ed015c8b [ 6.646045] [Hardware Error]: section length: 0x238 [ 6.651082] [Hardware Error]: 00000000: 72724502 5220726f 6f736165 6e55206e .Error Reason Un [ 6.659761] [Hardware Error]: 00000010: 776f6e6b 0000006e 00000000 00000000 known........... [ 6.668442] [Hardware Error]: 00000020: 00000000 00000000 00000000 00000000 ................ [ 6.677122] [Hardware Error]: 00000030: 00000000 00000000 00000000 00000000 ................
On Thu, 9 Nov 2017, James Morse wrote:
> Hi Manoj, > > On 08/11/17 19:05, Manoj Iyer wrote: >> On Thu, 2 Nov 2017, Shanker Donthineni wrote: >>> The ARM architecture defines the memory locations that are permitted >>> to be accessed as the result of a speculative instruction fetch from >>> an exception level for which all stages of translation are disabled. >>> Specifically, the core is permitted to speculatively fetch from the >>> 4KB region containing the current program counter and next 4KB. >>> >>> When translation is changed from enabled to disabled for the running >>> exception level (SCTLR_ELn[M] changed from a value of 1 to 0), the >>> Falkor core may errantly speculatively access memory locations outside >>> of the 4KB region permitted by the architecture. The errant memory >>> access may lead to one of the following unexpected behaviors. > >> I applied the 3 patches to Ubuntu 4.13.0-16-generic (Artful) kernel and >> ran stress-ng cpu tests on QDF2400 server > > [...] > >> Where stress-ng would spawn N workers and test cpu offline/online, perform >> matrix operations, do rapid context switchs, and anonymous mmaps. Although >> I was not able to reproduce the erratum on the stock 4.13 kernel using the >> same test case, the patched kernel did not seem to introduce any >> regressions either. I ran the stress-ng tests for over 8hrs found the >> system to be stable. > > > Could you throw kexec and KVM into the mix? This issue only shows up when we > disable the MMU, which we almost never do. > > For CPU offline/online we make the PSCI 'offline' call with the MMU enabled. > When the CPU comes back firmware has reset the EL2/EL1 SCTLR from a higher > exception level, so it won't hit this issue. > > One place we do this is kexec, where we drop into purgatory with the MMU disabled. > > The other is KVM unloading itself to return to the hyp stub. You can stress this > by starting and stopping a VM. When the number of VMs reaches 0 KVM should > unload via 'kvm_arch_hardware_disable()'. > > > Thanks, > > James > >
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