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arm64: Save state of HCR_EL2.E2H before switch to EL1 

As we're about to switch the way E2H-stuck CPUs boot, save
the boot CPU E2H state as a flag tied to the boot mode
that can then be checked by the idreg override code.

This allows us to replace the is_kernel_in_hyp_mode() check
with a simple comparison with this state, even when running
at EL1. Note that this flag isn't saved in __boot_cpu_mode,
and is only kept in a register in the assembly code.

Use with caution.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-3-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2022-06-30 17:04:53 +01:00 committed by Will Deacon
parent 7ddb0c3df7
commit b65e411d6c
3 changed files with 20 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/arm64/include/asm/virt.h
View File

@ -49,6 +49,13 @@
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)
/*
* Flags returned together with the boot mode, but not preserved in
* __boot_cpu_mode. Used by the idreg override code to work out the
* boot state.
*/
#define BOOT_CPU_FLAG_E2H BIT_ULL(32)
#ifndef __ASSEMBLY__
#include <asm/ptrace.h>

7
arch/arm64/kernel/head.S
View File

@ -457,6 +457,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
bl kasan_early_init
#endif
mov x0, x22 // pass FDT address in x0
mov x1, x20 // pass the full boot status
bl init_feature_override // Parse cpu feature overrides
mov x0, x20
bl finalise_el2 // Prefer VHE if possible
@ -479,8 +480,9 @@ SYM_FUNC_END(__primary_switched)
* Since we cannot always rely on ERET synchronizing writes to sysregs (e.g. if
* SCTLR_ELx.EOS is clear), we place an ISB prior to ERET.
*
* Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in w0 if
* booted in EL1 or EL2 respectively.
* Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in x0 if
* booted in EL1 or EL2 respectively, with the top 32 bits containing
* potential context flags. These flags are *not* stored in __boot_cpu_mode.
*/
SYM_FUNC_START(init_kernel_el)
mrs x0, CurrentEL
@ -545,6 +547,7 @@ __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)

11
arch/arm64/kernel/idreg-override.c
View File

@ -19,6 +19,8 @@
#define FTR_ALIAS_NAME_LEN 30
#define FTR_ALIAS_OPTION_LEN 116
static u64 __boot_status __initdata;
struct ftr_set_desc {
char name[FTR_DESC_NAME_LEN];
struct arm64_ftr_override *override;
@ -37,7 +39,8 @@ static bool __init mmfr1_vh_filter(u64 val)
* the user was trying to force nVHE on us, proceed with
* attitude adjustment.
*/
return !(is_kernel_in_hyp_mode() && val == 0);
return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
val == 0);
}
static const struct ftr_set_desc mmfr1 __initconst = {
@ -229,9 +232,9 @@ static __init void parse_cmdline(const void *fdt)
}
/* Keep checkers quiet */
void init_feature_override(const void *fdt);
void init_feature_override(const void *fdt, u64 boot_status);
asmlinkage void __init init_feature_override(const void *fdt)
asmlinkage void __init init_feature_override(const void *fdt, u64 boot_status)
{
int i;
@ -242,6 +245,8 @@ asmlinkage void __init init_feature_override(const void *fdt)
}
}
__boot_status = boot_status;
parse_cmdline(fdt);
for (i = 0; i < ARRAY_SIZE(regs); i++) {