Messages in this thread | | | Date | Fri, 6 May 2022 11:09:46 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v3] arm64: add the printing of tpidr_elx in __show_regs() |
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On Fri, May 06, 2022 at 04:16:55PM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/5/5 21:34, Leizhen (ThunderTown) wrote: > > On 2022/5/5 21:26, Leizhen (ThunderTown) wrote: > >> On 2022/5/5 21:04, Mark Rutland wrote: > >>> On Thu, May 05, 2022 at 05:56:40PM +0800, Zhen Lei wrote: > >>>> Commit 7158627686f0 ("arm64: percpu: implement optimised pcpu access > >>>> using tpidr_el1") and commit 6d99b68933fb ("arm64: alternatives: use > >>>> tpidr_el2 on VHE hosts") use tpidr_elx to cache my_cpu_offset to optimize > >>>> pcpu access. However, when performing reverse execution based on the > >>>> registers and the memory contents in kdump, this information is sometimes > >>>> required if there is a pcpu access. > >>>> > >>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > >>>> --- > >>>> arch/arm64/kernel/process.c | 5 +++++ > >>>> 1 file changed, 5 insertions(+) > >>>> > >>>> v2 --> v3: > >>>> 1) Relace "switch (read_sysreg(CurrentEL))" statement with > >>>> "if (is_kernel_in_hyp_mode())" statement. > >>>> 2) Change the register name to lowercase. > >>>> > >>>> v1 --> v2: > >>>> Directly print the tpidr_elx register of the current exception level. > >>>> Avoid coupling with the implementation of 'my_cpu_offset'. > >>>> > >>>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > >>>> index 7fa97df55e3ad3f..7b6bccce9721c36 100644 > >>>> --- a/arch/arm64/kernel/process.c > >>>> +++ b/arch/arm64/kernel/process.c > >>>> @@ -216,6 +216,11 @@ void __show_regs(struct pt_regs *regs) > >>>> show_regs_print_info(KERN_DEFAULT); > >>>> print_pstate(regs); > >>>> > >>>> + if (is_kernel_in_hyp_mode()) > >>>> + printk("tpidr_el2 : %016llx\n", read_sysreg(tpidr_el2)); > >>>> + else > >>>> + printk("tpidr_el1 : %016llx\n", read_sysreg(tpidr_el1)); > >>> > >>> If we care about the offset specifically, this would be simpler as: > >>> > >>> printk("cpu offset : 0x%016lx\n", __my_cpu_offset()); > >> > >> The function name is __show_regs(), so not using register name may not be good. > >> In fact, some other architectures may also have this problem. If we use my_cpu_offset, > >> we may need to put it in a public. > > > > The other idea is to back up each my_cpu_offset in an array. In this way, the offset can > > be queried through vmcore even if it is not printed. > > Sorry, __per_cpu_offset[NR_CPUS] is always defined.
Surely that's in the vmcore already? It's just data in memory.
Thanks, Mark.
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