On Thu, Oct 08, 2020 at 09:18:24PM -0400, Qian Cai wrote: > On Mon, 2020-10-05 at 17:43 +0100, Mark Rutland wrote: > > The current initialization of the per-cpu offset register is difficult > > to follow and this initialization is not always early enough for > > upcoming instrumentation with KCSAN, where the instrumentation callbacks > > use the per-cpu offset. > > > > To make it possible to support KCSAN, and to simplify reasoning about > > early bringup code, let's initialize the per-cpu offset earlier, before > > we run any C code that may consume it. To do so, this patch adds a new > > init_this_cpu_offset() helper that's called before the usual > > primary/secondary start functions. For consistency, this is also used to > > re-initialize the per-cpu offset after the runtime per-cpu areas have > > been allocated (which can change CPU0's offset). > > > > So that init_this_cpu_offset() isn't subject to any instrumentation that > > might consume the per-cpu offset, it is marked with noinstr, preventing > > instrumentation. > > > > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > > Cc: James Morse <james.morse@xxxxxxx> > > Cc: Will Deacon <will@xxxxxxxxxx> > > Reverting this commit on the top of today's linux-next fixed an issue that > Thunder X2 is unable to boot: > > .config: https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config > > EFI stub: Booting Linux Kernel... > EFI stub: EFI_RNG_PROTOCOL unavailable, KASLR will be disabled > EFI stub: Using DTB from configuration table > EFI stub: Exiting boot services and installing virtual address map... > > It hangs here for more than 10 minutes even with "earlycon" before I gave up. > The reverting makes it boot again following by those lines almost immediately. > > [ 0.000000][ T0] Booting Linux on physical CPU 0x0000000000 [0x431f0af1] > [ 0.000000][ T0] Linux version 5.9.0-rc8-next-20201008+ (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #6 SMP Thu Oct 8 20:57:40 EDT 2020 > [ 0.000000][ T0] efi: EFI v2.70 by American Megatrends > [ 0.000000][ T0] efi: ESRT=0xf9224418 SMBIOS=0xfcca0000 SMBIOS 3.0=0xfcc90000 ACPI 2.0=0xf9720000 MEMRESERVE=0xfc965918 > [ 0.000000][ T0] esrt: Reserving ESRT space from 0x00000000f9224418 to 0x00000000f9224450. > [ 0.000000][ T0] ACPI: Early table checksum verification disabled > [ 0.000000][ T0] ACPI: RSDP 0x00000000F9720000 000024 (v02 HPE ) > [ 0.000000][ T0] ACPI: XSDT 0x00000000F9720028 0000DC (v01 HPE ServerCL 01072009 AMI 00010013) > [ 0.000000][ T0] ACPI: FACP 0x00000000F9720108 000114 (v06 HPE ServerCL 01072009 AMI 00010013) > [ 0.000000][ T0] ACPI: DSDT 0x00000000F9720220 000714 (v02 HPE ServerCL 20150406 INTL 20170831) > [ 0.000000][ T0] ACPI: FIDT 0x00000000F9720938 00009C (v01 HPE ServerCL 01072009 AMI 00010013) Interesting... Could you provide a disassembly of init_this_cpu_offset() please? I was hoping to send the 5.10 pull request today, so I'll probably have to revert this change for now. Will
