On Thu, Feb 14, 2019 at 03:57:35PM +0100, Ard Biesheuvel wrote:
> On Thu, 14 Feb 2019 at 09:34, Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
> >
> > On Wed, Feb 13, 2019 at 02:27:37PM +0100, Ard Biesheuvel wrote:
> > > In the irqchip and EFI code, we have what basically amounts to a quirk
> > > to work around a peculiarity in the GICv3 architecture, which permits
> > > the system memory address of LPI tables to be programmable only once
> > > after a CPU reset. This means kexec kernels must use the same memory
> > > as the first kernel, and thus ensure that this memory has not been
> > > given out for other purposes by the time the ITS init code runs, which
> > > is not very early for secondary CPUs.
> > >
> > > On systems with many CPUs, these reservations could overflow the
> > > memblock reservation table, and this was addressed in commit
> > > eff896288872 ("efi/arm: Defer persistent reservations until after
> > > paging_init()"). However, this turns out to have made things worse,
> > > since the allocation of page tables and heap space for the resized
> > > memblock reservation table itself may overwrite the regions we are
> > > attempting to reserve, which may cause all kinds of corruption,
> > > also considering that the ITS will still be poking bits into that
> > > memory in response to incoming MSIs.
> > >
> > > So instead, let's grow the static memblock reservation table on such
> > > systems so it can accommodate these reservations at an earlier time.
> > > This will permit us to revert the above commit in a subsequent patch.
> > >
> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > > ---
> > > arch/arm64/include/asm/memory.h | 11 +++++++++++
> > > include/linux/memblock.h | 3 ---
> > > mm/memblock.c | 10 ++++++++--
> > > 3 files changed, 19 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > > index e1ec947e7c0c..7e2b13cdd970 100644
> > > --- a/arch/arm64/include/asm/memory.h
> > > +++ b/arch/arm64/include/asm/memory.h
> > > @@ -332,6 +332,17 @@ static inline void *phys_to_virt(phys_addr_t x)
> > > #define virt_addr_valid(kaddr) \
> > > (_virt_addr_is_linear(kaddr) && _virt_addr_valid(kaddr))
> > >
> > > +/*
> > > + * Given that the GIC architecture permits ITS implementations that can only be
> > > + * configured with a LPI table address once, GICv3 systems with many CPUs may
> > > + * end up reserving a lot of different regions after a kexec for their LPI
> > > + * tables, as we are forced to reuse the same memory after kexec (and thus
> > > + * reserve it persistently with EFI beforehand)
> > > + */
> > > +#if defined(CONFIG_EFI) && defined(CONFIG_ARM_GIC_V3_ITS)
> > > +#define INIT_MEMBLOCK_RESERVED_REGIONS (INIT_MEMBLOCK_REGIONS + 2 * NR_CPUS)
> > > +#endif
Not strictly related, with high NR_CPUS the memblock.reserved becomes quite
large and mostly empty in many cases. Is there a reason arm64 does not set
ARCH_DISCARD_MEMBLOCK?
> > > +
> > > #include <asm-generic/memory_model.h>
> > >
> > > #endif
> > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> > > index 64c41cf45590..859b55b66db2 100644
> > > --- a/include/linux/memblock.h
> > > +++ b/include/linux/memblock.h
> > > @@ -29,9 +29,6 @@ extern unsigned long max_pfn;
> > > */
> > > extern unsigned long long max_possible_pfn;
> > >
> > > -#define INIT_MEMBLOCK_REGIONS 128
> > > -#define INIT_PHYSMEM_REGIONS 4
> > > -
> > > /**
> > > * enum memblock_flags - definition of memory region attributes
> > > * @MEMBLOCK_NONE: no special request
> > > diff --git a/mm/memblock.c b/mm/memblock.c
> > > index 022d4cbb3618..a526c3ab8390 100644
> > > --- a/mm/memblock.c
> > > +++ b/mm/memblock.c
> > > @@ -26,6 +26,12 @@
> > >
> > > #include "internal.h"
> > >
> > > +#define INIT_MEMBLOCK_REGIONS 128
> > > +#define INIT_PHYSMEM_REGIONS 4
> > > +#ifndef INIT_MEMBLOCK_RESERVED_REGIONS
> > > +#define INIT_MEMBLOCK_RESERVED_REGIONS INIT_MEMBLOCK_REGIONS
> > > +#endif
> > > +
> >
> > I'd suggest
> >
> > s/INIT_MEMBLOCK_REGIONS/INIT_MEMORY_REGIONS
> > s/INIT_MEMBLOCK_RESERVED_REGIONS/INIT_RESERVED_REGIONS
> >
>
> Well, I'd prefer to keep MEMBLOCK in the identifier, given that we are
> setting it from an arch header file as well.
I was bothered by lack of consistency, but you're right, namespacing here
is more important.
Care to update /** DOC: */ section as a separate patch?
> > Except that,
> >
> > Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> >
>
> Thanks
>
>
> > > /**
> > > * DOC: memblock overview
> > > *
> > > @@ -92,7 +98,7 @@ unsigned long max_pfn;
> > > unsigned long long max_possible_pfn;
> > >
> > > static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
> > > -static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
> > > +static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_RESERVED_REGIONS] __initdata_memblock;
> > > #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> > > static struct memblock_region memblock_physmem_init_regions[INIT_PHYSMEM_REGIONS] __initdata_memblock;
> > > #endif
> > > @@ -105,7 +111,7 @@ struct memblock memblock __initdata_memblock = {
> > >
> > > .reserved.regions = memblock_reserved_init_regions,
> > > .reserved.cnt = 1, /* empty dummy entry */
> > > - .reserved.max = INIT_MEMBLOCK_REGIONS,
> > > + .reserved.max = INIT_MEMBLOCK_RESERVED_REGIONS,
> > > .reserved.name = "reserved",
> > >
> > > #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
> > > --
> > > 2.20.1
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
> >
>
--
Sincerely yours,
Mike.
