Messages in this thread | | | From | David Hildenbrand <> | Subject | Re: [PATCH v2 6/7] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE | Date | Mon, 1 Mar 2021 09:45:07 +0100 |
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On 26.02.21 13:04, Oscar Salvador wrote: > On Thu, Feb 25, 2021 at 07:29:07PM +0100, David Hildenbrand wrote: >> On 09.02.21 14:38, Oscar Salvador wrote: >>> Enable x86_64 platform to use the MHP_MEMMAP_ON_MEMORY feature. >>> >>> Signed-off-by: Oscar Salvador <osalvador@suse.de> >>> --- >>> arch/x86/Kconfig | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index 72663de8b04c..81046b7adb10 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -2440,6 +2440,10 @@ config ARCH_ENABLE_MEMORY_HOTREMOVE >>> def_bool y >>> depends on MEMORY_HOTPLUG >>> +config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE >>> + def_bool y >>> + depends on X86_64 && MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP_ENABLE >> >> It depends on SPARSEMEM_VMEMMAP, no? >> >> I think we could have >> >> SPARSEMEM_VMEMMAP_ENABLE=y >> and >> SPARSEMEM_VMEMMAP=n >> >> on manually tuned configs. > > I do not think this can happen: > > from mm/Kconfig: > > config SPARSEMEM_VMEMMAP_ENABLE > bool > > config SPARSEMEM_VMEMMAP > bool "Sparse Memory virtual memmap" > depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE > default y > help > SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise > pfn_to_page and page_to_pfn operations. This is the most > efficient option when sufficient kernel resources are available > > and from arch/x86/Kconfig: > > config ARCH_SPARSEMEM_ENABLE > def_bool y > depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD > select SPARSEMEM_STATIC if X86_32 > select SPARSEMEM_VMEMMAP_ENABLE if X86_64 > > > So, if I read this correctly, for SPARSEMEM_VMEMMAP to be true, > SPARSEMEM_VMEMMAP_ENABLE needs to be true as well. > > Am I missing something?
Take your config and set X86_5LEVEL=n (because it enforces SPARSEMEM_VMEMMAP) and SPARSEMEM_VMEMMAP=n
When compiling, you'll end up with a config like CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y # CONFIG_SPARSEMEM_VMEMMAP is not set
Yet, with your patch you would get
ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE=y
And it would not get fenced off in the code, right?
I think you either have to check (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) in addition in your code, or enforce it differently. Like
config MHP_MEMMAP_ON_MEMORY depends on SPARSEMEM_VMEMMAP && ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE bool
Then you can simplify the arch Kconfig settings, removing the sparesemem dependency there.
-- Thanks,
David / dhildenb
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