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SubjectRe: [RFC patch 00/15] entry: Provide generic implementation for host and guest entry/exit work
Hi Thomas,

As a heads-up, I'm going to be away next week, and I likely won't have
the chance to look at this in detail before October.

On Thu, Sep 19, 2019 at 05:03:14PM +0200, Thomas Gleixner wrote:
> When working on a way to move out the posix cpu timer expiry out of the
> timer interrupt context, I noticed that KVM is not handling pending task
> work before entering a guest. A quick hack was to add that to the x86 KVM
> handling loop. The discussion ended with a request to make this a generic
> infrastructure possible with also moving the per arch implementations of
> the enter from and return to user space handling generic.
>
> https://lore.kernel.org/r/89E42BCC-47A8-458B-B06A-D6A20D20512C@amacapital.net
>
> You asked for it, so don't complain that you have to review it :)

I never asked for this! ;)

> The series implements the syscall enter/exit and the general exit to
> userspace work handling along with the pre guest enter functionality.
>
> The series converts x86 and ARM64. x86 is fully tested including selftests
> etc. ARM64 is only compile tested for now as my only ARM64 testbox is not
> available right now.

I've been working on converting the arm64 entry code to C for a while
now [1], gradually upstreaming the bits I can.

James has picked up some of that [2] as a prerequisite for some RAS
error handling, and I think building the arm64 bits atop of that would
be preferable. IIUC that should get posted as a series come -rc1.

Since there's immense scope for subtle breakage, I'd prefer that we do
the arm64-specific asm->C conversion before migrating arm64 to generic
code. That way us arm64 folk can ensure the asm->C conversion retains
the existing behaviour, and it'll be easier for everyone to compare the
arm64 and generic C implementations.

Thanks,
Mark.

[1] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git
[2] git://linux-arm.org/linux-jm.git -b deasm_sync_only/v1

>
> Thanks,
>
> tglx
>
> ---
> /Makefile | 3
> arch/Kconfig | 3
> arch/arm64/Kconfig | 1
> arch/arm64/include/asm/kvm_host.h | 1
> arch/arm64/kernel/entry.S | 18 -
> arch/arm64/kernel/ptrace.c | 65 ------
> arch/arm64/kernel/signal.c | 45 ----
> arch/arm64/kernel/syscall.c | 49 ----
> arch/x86/Kconfig | 1
> arch/x86/entry/common.c | 265 +-------------------------
> arch/x86/entry/entry_32.S | 13 -
> arch/x86/entry/entry_64.S | 12 -
> arch/x86/entry/entry_64_compat.S | 21 --
> arch/x86/include/asm/signal.h | 1
> arch/x86/include/asm/thread_info.h | 9
> arch/x86/kernel/signal.c | 2
> arch/x86/kvm/x86.c | 17 -
> b/arch/arm64/include/asm/entry-common.h | 76 +++++++
> b/arch/x86/include/asm/entry-common.h | 104 ++++++++++
> b/include/linux/entry-common.h | 324 ++++++++++++++++++++++++++++++++
> b/kernel/entry/common.c | 220 +++++++++++++++++++++
> kernel/Makefile | 1
> 22 files changed, 776 insertions(+), 475 deletions(-)
>
>

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