LKML Archive on
help / color / mirror / Atom feed
From: Miroslav Benes <>
	Miroslav Benes <>
Subject: [PATCH v2 0/2] x86/xen: Make idle tasks reliable
Date: Thu, 19 Mar 2020 10:56:04 +0100	[thread overview]
Message-ID: <> (raw)

The unwinder reports idle tasks' stack on XEN PV as unreliable which
complicates things for at least live patching. The two patches in the
series try to amend that by using similar approach as non-XEN x86 does.

- call instruction used instead of push+jmp
- initial_stack used directly

There is a thing which makes me slightly uncomfortable. s/jmp/call/
means that, theoretically, the called function could return. GCC then
generates not so nice code and there is
asm_cpu_bringup_and_idle+0x5/0x1000 symbol last on the stack due to
alignment in asm/x86/xen/xen-head.S which could be confusing.
Practically it is all fine, because neither xen_start_kernel(), nor
cpu_bringup_and_idle() return (there is unbounded loop in
cpu_startup_entry() around do_idle()). __noreturn annotation of these
functions did not help.

So I don't think it is really a problem, but one may wonder.

Miroslav Benes (2):
  x86/xen: Make the boot CPU idle task reliable
  x86/xen: Make the secondary CPU idle tasks reliable

 arch/x86/xen/smp_pv.c   |  3 ++-
 arch/x86/xen/xen-head.S | 16 ++++++++++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)


             reply	other threads:[~2020-03-19  9:56 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19  9:56 Miroslav Benes [this message]
2020-03-19  9:56 ` [PATCH v2 1/2] x86/xen: Make the boot CPU idle task reliable Miroslav Benes
2020-03-19 10:01   ` Jan Beulich
2020-03-19 10:31     ` Miroslav Benes
2020-03-19  9:56 ` [PATCH v2 2/2] x86/xen: Make the secondary CPU idle tasks reliable Miroslav Benes
2020-03-19 10:03   ` Jan Beulich
2020-03-19 10:38     ` Miroslav Benes

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH v2 0/2] x86/xen: Make idle tasks reliable' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).