From: "Jürgen Groß" <jgross@suse.com>
To: Miroslav Benes <mbenes@suse.cz>,
boris.ostrovsky@oracle.com, sstabellini@kernel.org,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, jpoimboe@redhat.com
Cc: x86@kernel.org, xen-devel@lists.xenproject.org,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
jslaby@suse.cz
Subject: Re: [RFC PATCH 2/2] x86/xen: Make the secondary CPU idle tasks reliable
Date: Fri, 13 Mar 2020 09:26:58 +0100 [thread overview]
Message-ID: <75224ad1-f160-802a-9d72-b092ba864fb7@suse.com> (raw)
In-Reply-To: <20200312142007.11488-3-mbenes@suse.cz>
On 12.03.20 15:20, Miroslav Benes wrote:
> The unwinder reports the secondary CPU idle tasks' stack on XEN PV as
> unreliable, which affects at least live patching.
> cpu_initialize_context() sets up the context of the CPU through
> VCPUOP_initialise hypercall. After it is woken up, the idle task starts
> in cpu_bringup_and_idle() function and its stack starts at the offset
> right below pt_regs. The unwinder correctly detects the end of stack
> there but it is confused by NULL return address in the last frame.
>
> RFC: I haven't found the way to teach the unwinder about the state of
> the stack there. Thus the ugly hack using assembly. Similar to what
> startup_xen() has got for boot CPU.
>
> It introduces objtool "unreachable instruction" warning just right after
> the jump to cpu_bringup_and_idle(). It should show the idea what needs
> to be done though, I think. Ideas welcome.
>
> Signed-off-by: Miroslav Benes <mbenes@suse.cz>
> ---
> arch/x86/xen/smp_pv.c | 3 ++-
> arch/x86/xen/xen-head.S | 10 ++++++++++
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
> index 802ee5bba66c..6b88cdcbef8f 100644
> --- a/arch/x86/xen/smp_pv.c
> +++ b/arch/x86/xen/smp_pv.c
> @@ -53,6 +53,7 @@ static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
> static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
>
> static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
> +extern unsigned char asm_cpu_bringup_and_idle[];
>
> static void cpu_bringup(void)
> {
Would adding this here work?
+ asm volatile (UNWIND_HINT(ORC_REG_UNDEFINED, 0, ORC_TYPE_CALL, 1));
Juergen
next prev parent reply other threads:[~2020-03-13 8:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 14:20 [PATCH 0/2] x86/xen: Make idle tasks reliable Miroslav Benes
2020-03-12 14:20 ` [PATCH 1/2] x86/xen: Make the boot CPU idle task reliable Miroslav Benes
2020-03-12 15:04 ` [Xen-devel] " Andrew Cooper
2020-03-12 15:17 ` Miroslav Benes
2020-03-16 14:33 ` Boris Ostrovsky
2020-03-17 9:13 ` Miroslav Benes
2020-03-12 14:20 ` [RFC PATCH 2/2] x86/xen: Make the secondary CPU idle tasks reliable Miroslav Benes
2020-03-13 8:26 ` Jürgen Groß [this message]
2020-03-13 9:54 ` Miroslav Benes
2020-03-16 15:51 ` Miroslav Benes
2020-03-16 20:35 ` Josh Poimboeuf
2020-03-17 9:16 ` 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:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=75224ad1-f160-802a-9d72-b092ba864fb7@suse.com \
--to=jgross@suse.com \
--cc=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jpoimboe@redhat.com \
--cc=jslaby@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=mbenes@suse.cz \
--cc=mingo@redhat.com \
--cc=sstabellini@kernel.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).