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arm64: Allow sticky E2H when entering EL1 

For CPUs that have the unfortunate mis-feature to be stuck in
VHE mode, we perform a funny dance where we completely shortcut
the normal boot process to enable VHE and run the kernel at EL2,
and only then start booting the kernel.

Not only this is pretty ugly, but it means that the EL2 finalisation
occurs before we have processed the sysreg override.

Instead, start executing the kernel as if it was an EL1 guest and
rely on the normal EL2 finalisation to go back to EL2.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-4-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2022-06-30 17:04:54 +01:00 committed by Will Deacon
parent b65e411d6c
commit ae4b7e38e9
1 changed files with 10 additions and 24 deletions
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34
arch/arm64/kernel/head.S
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@ -511,6 +511,8 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
msr vbar_el2, x0
isb
mov_q x1, INIT_SCTLR_EL1_MMU_OFF
/*
* Fruity CPUs seem to have HCR_EL2.E2H set to RES1,
* making it impossible to start in nVHE mode. Is that
@ -520,35 +522,19 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
and x0, x0, #HCR_E2H
cbz x0, 1f
/* Switching to VHE requires a sane SCTLR_EL1 as a start */
mov_q x0, INIT_SCTLR_EL1_MMU_OFF
msr_s SYS_SCTLR_EL12, x0
/*
* Force an eret into a helper "function", and let it return
* to our original caller... This makes sure that we have
* initialised the basic PSTATE state.
*/
mov x0, #INIT_PSTATE_EL2
msr spsr_el1, x0
adr x0, __cpu_stick_to_vhe
msr elr_el1, x0
eret
/* Set a sane SCTLR_EL1, the VHE way */
msr_s SYS_SCTLR_EL12, x1
mov x2, #BOOT_CPU_FLAG_E2H
b 2f
1:
mov_q x0, INIT_SCTLR_EL1_MMU_OFF
msr sctlr_el1, x0
msr sctlr_el1, x1
mov x2, xzr
2:
msr elr_el2, lr
mov w0, #BOOT_CPU_MODE_EL2
orr x0, x0, x2
eret
__cpu_stick_to_vhe:
mov x0, #HVC_FINALISE_EL2
hvc #0
mov x0, #BOOT_CPU_MODE_EL2
orr x0, x0, #BOOT_CPU_FLAG_E2H
ret
SYM_FUNC_END(init_kernel_el)
/*