From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Ard Biesheuvel ardb@kernel.org
[ Upstream commit 7ba8f2b2d652cd8d8a2ab61f4be66973e70f9f88 ]
52-bit VA kernels can run on hardware that is only 48-bit capable, but configure the ID map as 52-bit by default. This was not a problem until recently, because the special T0SZ value for a 52-bit VA space was never programmed into the TCR register anwyay, and because a 52-bit ID map happens to use the same number of translation levels as a 48-bit one.
This behavior was changed by commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 from __cpu_set_tcr_t0sz()"), which causes the unsupported T0SZ value for a 52-bit VA to be programmed into TCR_EL1. While some hardware simply ignores this, Mark reports that Amberwing systems choke on this, resulting in a broken boot. But even before that commit, the unsupported idmap_t0sz value was exposed to KVM and used to program TCR_EL2 incorrectly as well.
Given that we already have to deal with address spaces being either 48-bit or 52-bit in size, the cleanest approach seems to be to simply default to a 48-bit VA ID map, and only switch to a 52-bit one if the placement of the kernel in DRAM requires it. This is guaranteed not to happen unless the system is actually 52-bit VA capable.
Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") Reported-by: Mark Salter msalter@redhat.com Link: http://lore.kernel.org/r/20210310003216.410037-1-msalter@redhat.com Signed-off-by: Ard Biesheuvel ardb@kernel.org Link: https://lore.kernel.org/r/20210310171515.416643-2-ardb@kernel.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/mmu_context.h | 5 +---- arch/arm64/kernel/head.S | 2 +- arch/arm64/mm/mmu.c | 2 +- 3 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index 0b3079fd28eb..1c364ec0ad31 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -65,10 +65,7 @@ extern u64 idmap_ptrs_per_pgd;
static inline bool __cpu_uses_extended_idmap(void) { - if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52)) - return false; - - return unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS)); + return unlikely(idmap_t0sz != TCR_T0SZ(vabits_actual)); }
/* diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 7ec430e18f95..a0b3bfe67609 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -319,7 +319,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ adrp x5, __idmap_text_end clz x5, x5 - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? + cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? b.ge 1f // .. then skip VA range extension
adr_l x6, idmap_t0sz diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index cb78343181db..6f0648777d34 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -40,7 +40,7 @@ #define NO_BLOCK_MAPPINGS BIT(0) #define NO_CONT_MAPPINGS BIT(1)
-u64 idmap_t0sz = TCR_T0SZ(VA_BITS); +u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
u64 __section(".mmuoff.data.write") vabits_actual;