From: Jan Beulich <jbeulich@suse.com>
To: "Jürgen Groß" <jgross@suse.com>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Jun Nakajima" <jun.nakajima@intel.com>,
xen-devel@lists.xenproject.org,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v6 09/12] xen: add runtime parameter access support to hypfs
Date: Thu, 5 Mar 2020 09:26:40 +0100 [thread overview]
Message-ID: <1c86f9c7-c2fd-e2d9-67ef-ceefa95a9851@suse.com> (raw)
In-Reply-To: <bd54ba1a-ce9e-35a3-3b15-82f74040baea@suse.com>
On 05.03.2020 07:01, Jürgen Groß wrote:
> On 04.03.20 17:56, Jan Beulich wrote:
>> On 04.03.2020 17:31, Jürgen Groß wrote:
>>> On 04.03.20 16:19, Jan Beulich wrote:
>>>> On 04.03.2020 16:07, Jürgen Groß wrote:
>>>>> On 04.03.20 12:32, Jan Beulich wrote:
>>>>>> On 26.02.2020 13:47, Juergen Gross wrote:
>>>>>>> +static void update_ept_param_append(const char *str, int val)
>>>>>>> +{
>>>>>>> + char *pos = opt_ept_setting + strlen(opt_ept_setting);
>>>>>>> +
>>>>>>> + snprintf(pos, sizeof(opt_ept_setting) - (pos - opt_ept_setting),
>>>>>>> + ",%s=%d", str, val);
>>>>>>> +}
>>>>>>> +
>>>>>>> +static void update_ept_param(void)
>>>>>>> +{
>>>>>>> + snprintf(opt_ept_setting, sizeof(opt_ept_setting), "pml=%d", opt_ept_pml);
>>>>>>> + if ( opt_ept_ad >= 0 )
>>>>>>> + update_ept_param_append("ad", opt_ept_ad);
>>>>>>
>>>>>> This won't correctly reflect reality: If you look at
>>>>>> vmx_init_vmcs_config(), even a negative value means "true" here,
>>>>>> unless on a specific Atom model. I think init_ept_param() wants
>>>>>> to have that erratum workaround logic moved there, such that
>>>>>> you can then assme the value to be non-negative here.
>>>>>
>>>>> But isn't not mentioning it in the -1 case correct? -1 means: do the
>>>>> correct thing on the current hardware.
>>>>
>>>> Well, I think the output here should represent effective settings,
>>>
>>> The minimum requirement is to reflect the effective parameters, like
>>> cmdline is doing for boot-time only parameters. With runtime parameters
>>> we had no way of telling what was set, and this is now possible.
>>>
>>>> and a sub-item should be suppressed only if a setting has no effect
>>>> at all in the current setup, like ...
>>>>
>>>>>>> + if ( opt_ept_exec_sp >= 0 )
>>>>>>> + update_ept_param_append("exec-sp", opt_ept_exec_sp);
>>>>>>
>>>>>> I agree for this one - if the value is still -1, it has neither
>>>>>> been set nor is its value of any interest.
>>>>
>>>> ... here.
>>>
>>> I think we should not mix up specified parameters and effective
>>> settings. In case an effective setting is of common interest it should
>>> be reported via a specific node (like e.g. specific mitigation settings
>>> where the cmdline is not providing enough details).
>>
>> But then a boolean option that wasn't specified on the command line
>> should produce no output at all. And hence we'd need a way to tell
>> whether an option was set from command line for _all_ of them. I
>> don't think this would be very helpful.
>
> I disagree here.
>
> This is important only for cases where the hypervisor treats the
> parameter as a tristate: true/false/unspecified. In all cases where
> the bool value is really true or false it can be reported as such.
The problem I'm having with this is the resulting inconsistency:
When we write the variable with 0 or 1 in case we find it to be
-1 after command line parsing, the externally visible effect will
be different from the case where we leave it to be -1 yet still
treat it as (pseudo-)boolean. This, however, is an implementation
detail, while imo the hypfs presentation should not depend on
such implementation details.
> Reporting 0/1 for e.g. "ad" if opt_ept_ad==-1 would add a latent problem
> if any other action would be derived from the parameter variable being
> -1.
>
> So either opt_ept_ad should be modified to change it to 0/1 instead of
> only setting the VCMS flag,
That's what I did suggest.
> or the logic should be kept as is in this
> patch. IMO changing the setting of opt_ept_ad should be done in another
> patch if this is really wanted.
And of course I don't mind at all doing so in a prereq patch.
It's just that the patch here provides a good place _where_ to
actually do such an adjustment.
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2020-03-05 8:27 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 12:46 [Xen-devel] [PATCH v6 00/12] Add hypervisor sysfs-like support Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 01/12] xen: allow only sizeof(bool) variables for boolean_param() Juergen Gross
2020-03-03 16:40 ` Jan Beulich
2020-03-09 11:43 ` Julien Grall
2020-03-09 11:55 ` Jan Beulich
2020-03-09 13:01 ` Jürgen Groß
2020-03-09 13:06 ` Jan Beulich
2020-03-09 14:06 ` Jürgen Groß
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 02/12] xen: add a generic way to include binary files as variables Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 03/12] docs: add feature document for Xen hypervisor sysfs-like support Juergen Gross
2020-03-09 11:48 ` Julien Grall
2020-03-25 14:05 ` Jürgen Groß
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 04/12] xen: add basic hypervisor filesystem support Juergen Gross
2020-03-03 16:59 ` Jan Beulich
2020-03-04 12:00 ` Jürgen Groß
2020-03-04 13:03 ` Jan Beulich
2020-03-04 14:39 ` Jürgen Groß
2020-03-04 15:07 ` Jan Beulich
2020-03-04 15:14 ` Jürgen Groß
2020-03-04 15:21 ` Jan Beulich
2020-03-06 6:06 ` Jürgen Groß
2020-03-06 8:19 ` Jan Beulich
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 05/12] libs: add libxenhypfs Juergen Gross
2020-02-26 12:46 ` [Xen-devel] [PATCH v6 06/12] tools: add xenfs tool Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 07/12] xen: provide version information in hypfs Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 08/12] xen: add /buildinfo/config entry to hypervisor filesystem Juergen Gross
2020-03-04 10:49 ` Jan Beulich
2020-03-04 12:06 ` Jürgen Groß
2020-03-04 13:04 ` Jan Beulich
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 09/12] xen: add runtime parameter access support to hypfs Juergen Gross
2020-03-04 11:32 ` Jan Beulich
2020-03-04 15:07 ` Jürgen Groß
2020-03-04 15:19 ` Jan Beulich
2020-03-04 16:31 ` Jürgen Groß
2020-03-04 16:56 ` Jan Beulich
2020-03-05 6:01 ` Jürgen Groß
2020-03-05 8:26 ` Jan Beulich [this message]
2020-03-06 6:42 ` Jürgen Groß
2020-03-06 8:20 ` Jan Beulich
2020-03-06 8:47 ` Jürgen Groß
2020-03-06 9:04 ` Jan Beulich
2020-03-06 9:20 ` Jürgen Groß
2020-03-06 9:22 ` Jan Beulich
2020-03-06 9:27 ` Jürgen Groß
2020-03-23 10:38 ` Julien Grall
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 10/12] tools/libxl: use libxenhypfs for setting xen runtime parameters Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 11/12] tools/libxc: remove xc_set_parameters() Juergen Gross
2020-02-26 12:47 ` [Xen-devel] [PATCH v6 12/12] xen: remove XEN_SYSCTL_set_parameter support Juergen Gross
2020-03-04 11:45 ` Jan Beulich
2020-03-04 14:40 ` Jürgen Groß
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=1c86f9c7-c2fd-e2d9-67ef-ceefa95a9851@suse.com \
--to=jbeulich@suse.com \
--cc=Volodymyr_Babchuk@epam.com \
--cc=andrew.cooper3@citrix.com \
--cc=george.dunlap@citrix.com \
--cc=ian.jackson@eu.citrix.com \
--cc=jgross@suse.com \
--cc=julien@xen.org \
--cc=jun.nakajima@intel.com \
--cc=kevin.tian@intel.com \
--cc=konrad.wilk@oracle.com \
--cc=roger.pau@citrix.com \
--cc=sstabellini@kernel.org \
--cc=wl@xen.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).