[PATCH 1/2] arm64: account for GICv3 LPI tables in static memblock reserve table

Ard Biesheuvel
2019-02-15T12:35:25Z

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.

Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
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..ada877f56551 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 (one per CPU), 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 + NR_CPUS + 1)
+#endif
+
#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
+
/**
* 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