[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH V3 (resend) 06/19] x86: Add a boot option to enable and disable the direct map
On 16.05.2024 11:19, Roger Pau Monné wrote: > On Wed, May 15, 2024 at 03:54:51PM +0200, Jan Beulich wrote: >> On 14.05.2024 11:20, Roger Pau Monné wrote: >>> On Mon, May 13, 2024 at 01:40:33PM +0000, Elias El Yandouzi wrote: >>>> --- a/docs/misc/xen-command-line.pandoc >>>> +++ b/docs/misc/xen-command-line.pandoc >>>> @@ -799,6 +799,18 @@ that enabling this option cannot guarantee anything >>>> beyond what underlying >>>> hardware guarantees (with, where available and known to Xen, respective >>>> tweaks applied). >>>> >>>> +### directmap (x86) >>>> +> `= <boolean>` >>>> + >>>> +> Default: `true` >>>> + >>>> +Enable or disable the directmap region in Xen. >>> >>> Enable or disable fully populating the directmap region in Xen. >> >> Elias, would you please take care to address earlier review comments >> before sending a new version? This and ... >> >>>> + >>>> +By default, Xen creates the directmap region which maps physical memory >>> ^ all? >>>> +in that region. Setting this to no will sparsely populate the directmap, >>> >>> "Setting this to no" => "Disabling this option will sparsely..." >> >> ... this is what I had already asked for in reply to v2, of course with >> different wording. >> >>>> --- a/xen/arch/x86/setup.c >>>> +++ b/xen/arch/x86/setup.c >>>> @@ -1517,6 +1517,8 @@ void asmlinkage __init noreturn __start_xen(unsigned >>>> long mbi_p) >>>> if ( highmem_start ) >>>> xenheap_max_mfn(PFN_DOWN(highmem_start - 1)); >>>> >>>> + printk("Booting with directmap %s\n", has_directmap() ? "on" : "off"); >>> >>> IMO this wants to be printed as part of the speculation mitigations, see >>> print_details() in spec_ctrl.c >> >> And not "on" / "off", but "full" / "sparse" (and word order changed >> accordingly) >> perhaps. > > I've been thinking about this, and I'm leaning towards calling this > new mode "ondemand" rather than "sparse". The fact that the direct > map ends up sparely populated is a consequence of populating it on > demand, and hence the later would be more descriptive IMO. > > (Same for the Kconfig option then ONDEMAND_DIRECTMAP, or some such) Fine with me, fwiw. Jan
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