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From: Dario Faggioli <dfaggioli@suse.com>
To: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: Joel Fernandes <joelaf@google.com>,
	"Yordan Karadzhov (VMware)" <y.karadz@gmail.com>,
	Linux Trace Devel <linux-trace-devel@vger.kernel.org>
Subject: Re: Instructions for clock sync for tracing host/guest
Date: Mon, 26 Apr 2021 16:11:46 +0200	[thread overview]
Message-ID: <af1e4b468e606be535227ae7fe8a1a17d4c019fb.camel@suse.com> (raw)
In-Reply-To: <CAPpZLN48S2M33sBR8tV4e1Wr1tHKj9rN0gb52nh3cbX_KBbGbw@mail.gmail.com>

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On Mon, 2021-04-26 at 15:59 +0300, Tzvetomir Stoyanov wrote:
> On Mon, Apr 26, 2021 at 3:44 PM Steven Rostedt <rostedt@goodmis.org>
> wrote:
> > 
> > 
> > We need to find a way to do this without qemu. It's only the thread
> > mapping
> > that is missing here, nothing else. And KVM sync should still work.
> 
> The problem is to find the VM specific directory in the KVM debugfs,
> where the VM TSC parameters are. The name of the directory is
> /sys/kernel/debug/kvm/<some PID>-<number>/
> The PID is the qemu process which runs the VM. I wonder how it looks
> in crosvm ?
> 
I can't double check as I don't have a crossvm environment handy, but I
guess it looks the same, and the PID is the one of whatever task in
crossvm issues the KVM_CREATE_VM ioctl (and the fd returned by such
call).

In QEMU, such process then creates one thread for each vCPU... Again, I
don't really know for sure, but I guess it would be similar in crossvm?

If yes, AFAICT, kvm_entry events can tell us the PIDs of such threads.
So the challenge here is getting from the PID of a thread to the PID of
the process that created it.

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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  reply	other threads:[~2021-04-26 14:11 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAJWu+opJEtyXyhYnKL1iNzhfSCYRZN4PD50igckVvQV8416HEQ@mail.gmail.com>
     [not found] ` <CAPpZLN5pTxjnrQ=x0Kq7sGko+GSVv5gPTjSgETvO9kX1hgNCpQ@mail.gmail.com>
     [not found]   ` <20210418080435.3c3e2d24@oasis.local.home>
     [not found]     ` <CAJWu+oqG9T5v_2q+crsrsPe9GMcG0OSW7kcZ5ea=r1L07WKZJA@mail.gmail.com>
     [not found]       ` <CAPpZLN7MDoFYaJZG1+_4gUpYwt2RfAMfB=BDvGYch2eOfS342Q@mail.gmail.com>
     [not found]         ` <CAJWu+oosbOV=cigwfkNBLSpaMt3RExWLap3u+4G7pkYqQy_EXw@mail.gmail.com>
     [not found]           ` <CAPpZLN7=e+TL5WY7RKAo9Hm6AJGDygneqUWwoNnZexx+=KrxsQ@mail.gmail.com>
     [not found]             ` <CAJWu+op2bU+-z6W_+XB0v2g__oGXj8Be2WWDg36E9uaCjNp+HA@mail.gmail.com>
     [not found]               ` <CAJWu+orm+tm3C=MSF=p9eC1qgfE_pXzA2B0CiXgVXFemVRiVtA@mail.gmail.com>
     [not found]                 ` <CAJWu+opzT20OprG-8L_Lvv2DaJzF-ROaKnEWX8wjrbagPpwVzA@mail.gmail.com>
     [not found]                   ` <CAJWu+oqJk+BE2q=CjtAZJko-kJCS0Kyqwor_FVM3fu-X-rRRkg@mail.gmail.com>
     [not found]                     ` <20210422153845.3e6e9304@gandalf.local.home>
     [not found]                       ` <CAJWu+ooTVfprhd49__0H_61Fz_rSQA53n-VM6e1eEr8cTZ5aYQ@mail.gmail.com>
     [not found]                         ` <20210422154830.52f3e4f5@gandalf.local.home>
     [not found]                           ` <CAJWu+oqYWv5OHTLrC+oa7Y+LOe7AHumhtyVP8TC2LkK2=_JjPA@mail.gmail.com>
     [not found]                             ` <20210422160313.2eee1f77@gandalf.local.home>
     [not found]                               ` <CAJWu+ooZ9UptDBdii7dj=ui7dhiseOqZJE1CqMhP-Zy98QueXA@mail.gmail.com>
     [not found]                                 ` <CAJWu+opsWVBDA8R-wVhhn2G_6h1LsMwzRDE=gMruZpFG+AH5zQ@mail.gmail.com>
     [not found]                                   ` <CAJWu+oo8W9TVexZhhOs4P-DW1bH5DSjAzuV8QZMxvt9XHbRnJg@mail.gmail.com>
2021-04-23  8:16                                     ` Instructions for clock sync for tracing host/guest Tzvetomir Stoyanov
     [not found]                                       ` <CAJWu+orjdLAdcUJKWj6f8gUtXUzBcvJEPeKjtVZ7P+EpiptF0w@mail.gmail.com>
2021-04-23 11:33                                         ` Steven Rostedt
2021-04-23 15:49                                           ` Joel Fernandes
2021-04-26 10:58                                         ` Tzvetomir Stoyanov
2021-04-26 12:44                                           ` Steven Rostedt
2021-04-26 12:59                                             ` Tzvetomir Stoyanov
2021-04-26 14:11                                               ` Dario Faggioli [this message]
2021-04-26 14:51                                                 ` Steven Rostedt
2021-04-26 15:02                                                   ` Tzvetomir Stoyanov
2021-04-26 15:31                                                     ` Steven Rostedt
2021-04-26 15:37                                                       ` Steven Rostedt
2021-04-26 15:44                                                       ` Dario Faggioli
2021-04-26 15:38                                                     ` Dario Faggioli
2021-04-26 15:50                                                       ` Steven Rostedt
2021-04-26 16:10                                                         ` Dario Faggioli
2021-04-25 18:29                                       ` Steven Rostedt
2021-04-26 10:39                                         ` Tzvetomir Stoyanov
2021-04-26 12:56                                           ` Steven Rostedt
2021-04-26 13:24                                             ` Dario Faggioli
2021-04-26 13:51                                               ` Tzvetomir Stoyanov

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