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Subject[PATCH V7 0/6] x86/entry: Clean up entry code
Date
From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

This patchset moves the stack-switch code to the place where
error_entry() return, unravels error_entry() from XENpv and makes
entry_INT80_compat() uses idtentry macro.

This patchset is highly related to XENpv, because it does the extra
cleanup to convert SWAPGS to swapgs after major cleanup is done.

The patches are the 7th version to pick patches from the patchset
https://lore.kernel.org/lkml/20211126101209.8613-1-jiangshanlai@gmail.com/
which converts ASM code to C code. These patches are prepared for that
purpose. But this patchset has it own value: it simplifies the stack
switch, avoids leaving the old stack inside a function call, and
separates XENpv code with native code without adding new code.

Peter said in V3:
> So AFAICT these patches are indeed correct.
>
> I'd love for some of the other x86 people to also look at this,
> but a tentative ACK on this.

[V6]: https://lore.kernel.org/lkml/20220421141055.316239-1-jiangshanlai@gmail.com/
[V5]: https://lore.kernel.org/lkml/20220412121541.4595-1-jiangshanlai@gmail.com/
[V4]: https://lore.kernel.org/lkml/20220318143016.124387-1-jiangshanlai@gmail.com/
[V3]: https://lore.kernel.org/lkml/20220315073949.7541-1-jiangshanlai@gmail.com/
[V2]: https://lore.kernel.org/lkml/20220303035434.20471-1-jiangshanlai@gmail.com/
[V1]: https://lore.kernel.org/lkml/20211208110833.65366-1-jiangshanlai@gmail.com/


Changed from V6:
(no code changed)

Update the changelog of patch3 and patch6

Drop patch7 and patch8 of the V6. The patch7/8 are nice cleanup
patches but they are not required to convert error_entry() to C.
The changelog of patch8 is also updated locally to avoid ambiguity
that tglx questioned, and it will be sent separately after PeterZ's
change to entry_INT80_compat() merged to avoid confliction.

Changed from V5:
Add a new ASM function to wrap PUSH_AND_CLEAR_REGS rather than
inline it in the marco idtentry to reduce text size.

Remove the branch in sync_regs() (pick it from V1 and update
the changelog a little)

Changed from V4:
Update changelog largely of patch 1 and patch 2
Update changelog slightly of other patches
Unbreak the line of fixup_bad_iret() in patch1

Add Reviewed-by from Juergen Gross <jgross@suse.com> in patch 6
since he gave the Reviewed-by in one of the squashed patches.

Changed from V3:
Only reorder the int80 thing as the last patch to make patches
ordering more natural. (Both orders are correct)

Other interactions in V3:
Peter raised several questions and I think I answered them and I
don't think the code need to be updated unless I missed some
points. (Except reordering the patches)

Josh asked to remove UNWIND_HINT_REGS in patch5, but I think
UNWIND_HINT_REGS is old code before this patchset and I don't
want to do a cleanup that is not relate to preparing converting
ASM code C code in this patchset. He also asked to remove
ENCODE_FRAME_POINTER in xenpv case, and I think it just
complicates the code for just optimizing out a single assignment
to %rbp. I would not always stick to these reasons of mine,
but I just keep the code unchanged since he hasn't emphasized it
again nor other people has requested it.

Changed from V2:
Make the patch of folding int80 thing as the first patch
Add more changelog in "Switch the stack after error_entry() returns"

Changed from V1
Squash cleanup patches converting SWAPGS to swapgs into one patch

Use my official email address (Ant Group). The work is backed
by my company and I was incorrectly misunderstood that
XXX@linux.alibaba.com is the only portal for opensource work
in the corporate group.


Lai Jiangshan (6):
x86/traps: Move pt_regs only in fixup_bad_iret()
x86/entry: Switch the stack after error_entry() returns
x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()
x86/entry: Move cld to the start of idtentry macro
x86/entry: Don't call error_entry() for XENPV
x86/entry: Convert SWAPGS to swapgs and remove the definition of
SWAPGS

arch/x86/entry/entry_64.S | 53 ++++++++++++++++++++++----------
arch/x86/entry/entry_64_compat.S | 2 +-
arch/x86/include/asm/irqflags.h | 8 -----
arch/x86/include/asm/traps.h | 2 +-
arch/x86/kernel/traps.c | 18 ++++-------
5 files changed, 44 insertions(+), 39 deletions(-)

--
2.19.1.6.gb485710b

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