Re: [patch 00/10] x86/entry: Consolidation - Part I

Alexandre Chartre
2020-02-27T11:02:17Z

On 2/25/20 10:36 PM, Thomas Gleixner wrote:
> Hi!
>
> This is the first batch of a 73 patches series which consolidates the x86
> entry code.
>
> This work started off as a trivial 5 patches series moving the heavy
> lifting of POSIX CPU timers out of interrupt context into thread/process
> context. This discovered that KVM is lacking to handle pending work items
> before entering guest mode and added the handling to the x86 KVM
> code. Review requested to make this a generic infrastructure.
>
> The next series grew to 25 patches implementing the generic infrastructure,
> converting x86 (and as a POC ARM64) over, but it turned out that this was
> slightly incomplete and still had some entanglement with the rest of the
> x86 entry code as some of that functionality is shared between syscall and
> interrupt entry/exit. And it also unearthed the nastyness of IOPL which got
> already addressed in mainline.
>
> This series addresses these issues in order to prepare for making the entry
> from userspace and exit to userspace (and it's counterpart enter guest) a
> generic infrastructure in order to restrict the necessary ASM work to the
> bare minimum.
>
> The series is split into 5 parts:
>
> - General cleanups and bugfixes
>
> - Consolidation of the syscall entry/exit code
>
> - Autogenerate simple exception/trap code and reduce the difference
> between 32 and 64 bit
>
> - Autogenerate complex exception/trap code and provide different entry
> points for #DB and #MC exceptions which allows to address the
> recently discovered RCU vs. world issues in a more structured way
>
> - Convert the device interrupt entry code to use the same mechanism as
> exceptions and traps and finally convert the system vectors over as
> well. The last step after all those cleanups is to move the return
> from exception/interrupt logic (user mode work, kernel preemption)
> completely from ASM into C-code, so the ASM code just has to take
> care about returning from the exception, which is horrible and
> convoluted enough already.
>
> At the end the x86 entry code is ready to move the syscall parts out into
> generic code and finally tackle the initial problem which started all of
> this.
>
> The complete series is available from git:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/entry
>
> which contains all 73 patches. The individual parts are tagged, so this
> part can be retrieved via:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v1-part1
>
> Thanks,
>
> tglx
>
> 8<---------------
> entry/entry_32.S | 19 +++++++------------
> include/asm/irq.h | 2 +-
> include/asm/mce.h | 3 ---
> include/asm/traps.h | 17 +++++++----------
> kernel/cpu/mce/core.c | 12 ++++++++++--
> kernel/cpu/mce/internal.h | 3 +++
> kernel/irq.c | 3 +--
> kernel/traps.c | 41 ++++++++++++++++++++++++++++++++++-------
> 8 files changed, 63 insertions(+), 37 deletions(-)
>

For part I:

Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>

for all patches. I had a slight concern about patch 08 and propagating a different
error_code, but I agree with your argument that it is limited to 32-bit process and
now matches with the 64-bit behavior.

alex.