Re: [PATCH v1 0/3] x86: Allow variable-sized event frame

[Xin Li <xin@zytor.com>]

On 8/26/2024 10:32 AM, Xin Li wrote:
> On 6/17/2024 1:45 AM, Xin Li (Intel) wrote:
>> This was initially posted as part of the FRED patch series and turned
>> down due to its unacceptable quality:
>>    https://lore.kernel.org/lkml/20230410081438.1750-31-xin3.li@intel.com/
>>
>> And this is another attempt to meet the bar.
>>
> 
> I'm expecting to get some review comments on this patch set :-)

Try to get some reviews again :)

> 
>>
>> a FRED event frame could contain different amount of information for
>> different event types, e.g., #MCE could push extra bytes of information,
>> or perhaps even for different instances of the same event type. Thus
>> the size of an event frame pushed by a FRED CPU is not fixed and the
>> address of a pt_regs structure that is used to save the user level
>> context of current task is not at a fixed offset from top of current
>> task kernel stack.
>>
>> This patch set adds a new field named 'user_pt_regs' in the thread_info
>> structure to save the address of user level context pt_regs structure,
>> thus to eliminate the need of any advance information of event frame
>> size and allow a FRED CPU to push variable-sized event frame.
>>
>> With the above change, we can
>> 1) Remove the padding space at top of the init stack because there is
>>     no user level context for init task.
>> 2) Get rid of TOP_OF_KERNEL_STACK_PADDING on x86_64, which was defined
>>     to 0 for IDT to keep the code consistent with 32bit.
>>
>>
>> Xin Li (Intel) (3):
>>    x86/fred: Allow variable-sized event frame
>>    x86: Remove the padding space at top of the init stack
>>    x86: Get rid of TOP_OF_KERNEL_STACK_PADDING on x86_64
>>
>>   arch/x86/entry/entry_fred.c        | 22 +++++++++++++++++
>>   arch/x86/include/asm/processor.h   | 38 +++++++++++++++++++++++-------
>>   arch/x86/include/asm/switch_to.h   |  2 +-
>>   arch/x86/include/asm/thread_info.h | 19 +++++----------
>>   arch/x86/kernel/process.c          | 21 +++++++++++++++++
>>   arch/x86/kernel/vmlinux.lds.S      | 18 ++++++++++++--
>>   include/linux/thread_info.h        |  1 +
>>   kernel/fork.c                      |  6 +++++
>>   8 files changed, 102 insertions(+), 25 deletions(-)
>>
>>
>> base-commit: 49b33979e3bf0a5424420d14f026de12f34e8b1e
> 
>