On Fri, 4 Dec 2015 09:20:50 +0100
Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> * Igor Mammedov <imammedo@xxxxxxxxxx> wrote:
>
> > diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
> > index 94c18eb..53d7951 100644
> > --- a/arch/x86/include/asm/acpi.h
> > +++ b/arch/x86/include/asm/acpi.h
> > @@ -147,6 +147,7 @@ static inline void disable_acpi(void) { }
> > #ifdef CONFIG_ACPI_NUMA
> > extern int acpi_numa;
> > extern int x86_acpi_numa_init(void);
> > +unsigned long acpi_get_max_possible_pfn(void);
> > #endif /* CONFIG_ACPI_NUMA */
> >
> > #define acpi_unlazy_tlb(x) leave_mm(x)
> > @@ -170,4 +171,8 @@ static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> > }
> > #endif
> >
> > +#ifdef CONFIG_ACPI_HOTPLUG_MEMORY
> > +extern bool acpi_no_memhotplug;
> > +#endif /* CONFIG_ACPI_HOTPLUG_MEMORY */
> > +
> > #endif /* _ASM_X86_ACPI_H */
> > diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> > index adf0392..61d5ba5 100644
> > --- a/arch/x86/kernel/pci-swiotlb.c
> > +++ b/arch/x86/kernel/pci-swiotlb.c
> > @@ -88,7 +88,11 @@ int __init pci_swiotlb_detect_4gb(void)
> > {
> > /* don't initialize swiotlb if iommu=off (no_iommu=1) */
> > #ifdef CONFIG_X86_64
> > +#ifdef CONFIG_ACPI_NUMA
> > + if (!no_iommu && acpi_get_max_possible_pfn() > MAX_DMA32_PFN)
> > +#else
> > if (!no_iommu && max_pfn > MAX_DMA32_PFN)
> > +#endif
> > swiotlb = 1;
> > #endif
> > return swiotlb;
> > diff --git a/arch/x86/mm/srat.c b/arch/x86/mm/srat.c
> > index c2aea63..21b33f0 100644
> > --- a/arch/x86/mm/srat.c
> > +++ b/arch/x86/mm/srat.c
> > @@ -153,10 +153,20 @@ acpi_numa_processor_affinity_init(struct acpi_srat_cpu_affinity *pa)
> >
> > #ifdef CONFIG_MEMORY_HOTPLUG
> > static inline int save_add_info(void) {return 1;}
> > +static unsigned long max_possible_pfn __initdata;
> > #else
> > static inline int save_add_info(void) {return 0;}
> > #endif
> >
> > +unsigned long __init acpi_get_max_possible_pfn(void)
> > +{
> > +#ifdef CONFIG_ACPI_HOTPLUG_MEMORY
> > + if (!acpi_no_memhotplug)
> > + return max_possible_pfn;
> > +#endif
> > + return max_pfn;
> > +}
> > +
> > /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
> > int __init
> > acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
> > @@ -203,6 +213,11 @@ acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
> > pr_warn("SRAT: Failed to mark hotplug range [mem %#010Lx-%#010Lx] in memblock\n",
> > (unsigned long long)start, (unsigned long long)end - 1);
> >
> > +#ifdef CONFIG_MEMORY_HOTPLUG
> > + if (max_possible_pfn < PFN_UP(end - 1))
> > + max_possible_pfn = PFN_UP(end - 1);
> > +#endif
> > +
> > return 0;
> > out_err_bad_srat:
> > bad_srat();
> > diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> > index 6b0d3ef..ae38f57 100644
> > --- a/drivers/acpi/acpi_memhotplug.c
> > +++ b/drivers/acpi/acpi_memhotplug.c
> > @@ -357,7 +357,7 @@ static void acpi_memory_device_remove(struct acpi_device *device)
> > acpi_memory_device_free(mem_device);
> > }
> >
> > -static bool __initdata acpi_no_memhotplug;
> > +bool __initdata acpi_no_memhotplug;
> >
> > void __init acpi_memory_hotplug_init(void)
> > {
>
> So I don't disagree with the fix in principle, but the implementation here is
> rather ugly - it spreads new non-obvious #ifdefs across various critical parts of
> the kernel.
>
> For example this:
>
> > #ifdef CONFIG_X86_64
> > +#ifdef CONFIG_ACPI_NUMA
> > + if (!no_iommu && acpi_get_max_possible_pfn() > MAX_DMA32_PFN)
> > +#else
> > if (!no_iommu && max_pfn > MAX_DMA32_PFN)
> > +#endif
> > swiotlb = 1;
> > #endif
>
> could be cleaned up by introducing a proper max_possible_pfn variable, and setting
> it from the ACPI code - instead of exporting acpi_get_max_possible_pfn().
Thanks for review,
I'll try to drop #ifdefs as suggested and split it
in several patches.
>
> Another pattern is:
>
> > +#ifdef CONFIG_ACPI_HOTPLUG_MEMORY
> > + if (!acpi_no_memhotplug)
on the second thought,
we don't need need this knob to force disabling
SWIOTLB initialization since there is an existing
"no_iommu" option to do it, so I'll drop this check.
> > + return max_possible_pfn;
> > +#endif
>
> this should be driven from the acpi_no_memhotplug knob, instead of spreading
> acpi_no_memhotplug uses to other callsites.
>
> Furthermore, please split these various steps up into multiple steps (and first do
> the preparatory changes, then fix the bug in the end) - to make it easier to
> bisect and analyze if we regress existing functionality somewhere.
>
> Thanks,
>
> Ingo
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