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| author | Ard Biesheuvel <ardb@kernel.org> | 2021-03-10 20:15:11 +0300 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-03-11 16:04:28 +0300 |
| commit | 7ba8f2b2d652cd8d8a2ab61f4be66973e70f9f88 (patch) | |
| tree | 85b24dcd8d1f5b89def949ad4306bc54b9d46182 /arch/arm64/kernel/head.S | |
| parent | 7bb8bc6eb550116c504fb25af8678b9d7ca2abc5 (diff) | |
| download | linux-7ba8f2b2d652cd8d8a2ab61f4be66973e70f9f88.tar.xz | |
arm64: mm: use a 48-bit ID map when possible on 52-bit VA builds
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>
Diffstat (limited to 'arch/arm64/kernel/head.S')
| -rw-r--r-- | arch/arm64/kernel/head.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 8b469f164091..840bda1869e9 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 |