On 17/01/2019 10:08, Andrew Cooper wrote: > On 17/01/2019 08:43, Roger Pau Monné wrote: >> On Wed, Jan 16, 2019 at 07:51:33PM +0000, Andrew Cooper wrote: >>> On 16/01/2019 11:52, Jan Beulich wrote: >>>>>>> On 16.01.19 at 10:00, <andrew.coop...@citrix.com> wrote: >>>>> --- a/docs/misc/xen-command-line.pandoc >>>>> +++ b/docs/misc/xen-command-line.pandoc >>>>> @@ -636,61 +636,83 @@ trace feature is only enabled in debugging builds >>>>> of Xen. >>>>> >>>>> Specify the bit width of the DMA heap. >>>>> >>>>> -### dom0 (x86) >>>>> -> `= List of [ pvh | shadow | verbose ]` >>>>> +### dom0 >>>>> + = List of [ pvh=<bool>, shadow=<bool>, verbose=<bool> ] >>>>> >>>>> -> Sub-options: >>>>> + Applicability: x86 >>>>> >>>>> -> `pvh` >>>>> +Controls for how dom0 is constructed on x86 systems. >>>>> >>>>> -> Default: `false` >>>>> +* The `pvh` boolean controls whether dom0 is constructed as a PV or a >>>>> PVH >>>>> + guest. The default is PV. In addition, the following requirements >>>>> must >>>>> + be met: >>>>> >>>>> -Flag that makes a dom0 boot in PVHv2 mode. >>>>> + * The dom0 kernel selected by the boot loader must be capable of >>>>> the >>>>> + selected mode. >>>>> + * For a PV dom0, Xen must have been compiled with `CONFIG_PV` >>>>> enabled. >>>>> + * For a PVH dom0, Xen must have been compiled with `CONFIG_HVM` >>>>> enabled, >>>>> + and the hardware must have VT-x/SVM extensions available. >>>>> >>>>> -> `shadow` >>>>> +* The `shadow` boolean is only applicable when dom0 is constructed as >>>>> a PVH >>>>> + guest, and controls whether dom0 uses hardware assisted paging, or >>>>> shadow >>>>> + paging. The default is HAP when available, and shadow otherwise. >>>>> >>>>> -> Default: `false` >>>>> + This option is unavailable when `CONFIG_SHADOW_PAGING` is compiled >>>>> out. A >>>>> + PVH dom0 cannot be used if `CONFIG_SHADOW_PAGING` is compiled out, >>>>> and the >>>>> + hardware is not HAP-capable. >>>> As mentioned elsewhere, I object to adding CONFIG_* into this doc, >>>> which is intended to be meaningful to non-developers. But not to the >>>> degree of NAK-ing the whole thing, if everyone else disagrees with me. >>> I'm not sure what else to say. I object to purposefully omitting >>> relevant information from our documentation. >> Maybe it would be helpful to add some kind of tag that could >> standardize the relationship between Kconfig options and command line >> options? >> >> Kconfig: SHADOW_PAGING >> >> Or similar. This would get the specific Kconfig details out of the >> general description of the functionality, thus not harming readability >> by non-expert users? >> >> Using such tag would require some explanation of it's meaning at the >> top of the document. >> >>> Most people reading it, including non-developers, will know what Kconfig >>> is and how to check, owing to at least a basic knowledge of Linux. >>> Those that don't will be capable of basic human interaction such as >>> asking a question of someone more knowledgeable. >> If the above is not suitable, I might suggest to reword the sentence >> as: >> >> "This option is unavailable when the Kconfig `SHADOW_PAGING` option is >> not selected at build time." >> >> Explicitly mentioning Kconfig and selected simplifies the language for >> non-expert users IMO, and makes it clear this is exclusively a build >> time decision. Note I'm not a native speaker, so my sense of easier to >> understand could be completely wrong. > > I have a rewrite of the head of the document pending anyway which I hope > to get sorted properly for 4.12 > > While having a Kconfig: section would probably be fine for ~80% of the > simple cases, it doesn't work for this patch. > > I guess the root of the issue is that I do not believe that phrasing the > information like this makes it harder for non-expert users > read/comprehend, and there definitely are a group of readers for which > this information is relevant.
In any case I'd prefer to spell out the complete config option (e.g. CONFIG_FOO) in case we ever get a way to read the config from the running hypervisor (FWIW I'm just writing a series for doing that). Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
