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

[Xin Li]

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@xxxxxxxxx/
> >
> > 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