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| author | Pingfan Liu <kernelfans@gmail.com> | 2020-08-28 21:39:57 +0800 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-09-11 19:06:25 +0100 |
| commit | 72789a4a6a914601912a8992b0d43bd5abc05128 (patch) | |
| tree | 675a43908a89b7ef8af71855e98177f00c7b7022 /arch/arm64/kernel/cpu-reset.S | |
| parent | f75aef392f869018f78cfedf3c320a6b3fcfda6b (diff) | |
| download | linux-72789a4a6a914601912a8992b0d43bd5abc05128.tar.bz2 | |
arm64/relocate_kernel: remove redundant code
Kernel startup entry point requires disabling MMU and D-cache.
As for kexec-reboot, taking a close look at "msr sctlr_el1, x12" in
__cpu_soft_restart as the following:
-1. booted at EL1
The instruction is enough to disable MMU and I/D cache for
EL1 regime.
-2. booted at EL2, using VHE
Access to SCTLR_EL1 is redirected to SCTLR_EL2 in EL2. So the instruction
is enough to disable MMU and clear I+C bits for EL2 regime.
-3. booted at EL2, not using VHE
The instruction itself can not affect EL2 regime. But The hyp-stub doesn't
enable the MMU and I/D cache for EL2 regime. And KVM also disable them for EL2
regime when its unloaded, or execute a HVC_SOFT_RESTART call. So when
kexec-reboot, the code in KVM has prepare the requirement.
As a conclusion, disabling MMU and clearing I+C bits in
SYM_CODE_START(arm64_relocate_new_kernel) is redundant, and can be removed
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: James Morse <james.morse@arm.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Remi Denis-Courmont <remi.denis.courmont@huawei.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: kvmarm@lists.cs.columbia.edu
Link: https://lore.kernel.org/r/1598621998-20563-1-git-send-email-kernelfans@gmail.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/cpu-reset.S')
| -rw-r--r-- | arch/arm64/kernel/cpu-reset.S | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S index 4a18055b2ff9..37721eb6f9a1 100644 --- a/arch/arm64/kernel/cpu-reset.S +++ b/arch/arm64/kernel/cpu-reset.S @@ -35,6 +35,10 @@ SYM_CODE_START(__cpu_soft_restart) mov_q x13, SCTLR_ELx_FLAGS bic x12, x12, x13 pre_disable_mmu_workaround + /* + * either disable EL1&0 translation regime or disable EL2&0 translation + * regime if HCR_EL2.E2H == 1 + */ msr sctlr_el1, x12 isb |