[PATCH] arm64: Disable fine grained traps on boot
Marc Zyngier
maz at kernel.org
Thu Apr 1 16:14:35 BST 2021
Thanks Will for the bounce.
On Thu, 01 Apr 2021 13:49:36 +0100,
Mark Brown <broonie at kernel.org> wrote:
>
> The arm64 FEAT_FGT extension introduces a set of traps to EL2 for accesses
> to small sets of registers and instructions from EL1 and EL0. Currently
> Linux makes no use of this feature, ensure that it is not active at boot by
> disabling the traps during EL2 setup.
>
> Signed-off-by: Mark Brown <broonie at kernel.org>
> ---
> arch/arm64/include/asm/el2_setup.h | 21 +++++++++++++++++++++
> arch/arm64/include/asm/sysreg.h | 6 ++++++
> 2 files changed, 27 insertions(+)
>
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index d77d358f9395..f94ef3a76877 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -131,6 +131,26 @@
> .Lskip_sve_\@:
> .endm
>
> +/* Disable any fine grained traps */
> +.macro __init_el2_fgt
> + mrs x1, id_aa64mmfr0_el1
> + ubfx x1, x1, #ID_AA64MMFR0_FGT_SHIFT, #4
> + cbz x1, .Lskip_fgt_\@
> +
> + msr_s SYS_HDFGRTR_EL2, xzr
> + msr_s SYS_HDFGWTR_EL2, xzr
> + msr_s SYS_HFGRTR_EL2, xzr
> + msr_s SYS_HFGITR_EL2, xzr
> + msr_s SYS_HFGWTR_EL2, xzr
nit: consider grouping SYS_HFGWTR_EL2 and SYS_HFGRTR_EL2 together,
since they affect the same registers.
> +
> + mrs x1, id_aa64pfr0_el1 // AMU traps UNDEF without AMU
> + ubfx x1, x1, #ID_AA64PFR0_AMU_SHIFT, #4
> + cbz x1, .Lskip_fgt_\@
> +
> + msr_s SYS_HAFGRTR_EL2, xzr
Do we need to document the need for SCR_EL3.FGTEn to be set so that
these register accesses don't trap? That'd be consistent with what we
do for other features (PtrAuth, AMU...).
> +.Lskip_fgt_\@:
> +.endm
> +
> .macro __init_el2_nvhe_prepare_eret
> mov x0, #INIT_PSTATE_EL1
> msr spsr_el2, x0
> @@ -155,6 +175,7 @@
> __init_el2_nvhe_idregs
> __init_el2_nvhe_cptr
> __init_el2_nvhe_sve
> + __init_el2_fgt
> __init_el2_nvhe_prepare_eret
> .endm
>
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index d4a5fca984c3..b35468927363 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -475,9 +475,15 @@
> #define SYS_PMCCFILTR_EL0 sys_reg(3, 3, 14, 15, 7)
>
> #define SYS_SCTLR_EL2 sys_reg(3, 4, 1, 0, 0)
> +#define SYS_HFGRTR_EL2 sys_reg(3, 4, 1, 1, 4)
> +#define SYS_HFGWTR_EL2 sys_reg(3, 4, 1, 1, 5)
> +#define SYS_HFGITR_EL2 sys_reg(3, 4, 1, 1, 6)
> #define SYS_ZCR_EL2 sys_reg(3, 4, 1, 2, 0)
> #define SYS_TRFCR_EL2 sys_reg(3, 4, 1, 2, 1)
> #define SYS_DACR32_EL2 sys_reg(3, 4, 3, 0, 0)
> +#define SYS_HDFGRTR_EL2 sys_reg(3, 4, 3, 1, 4)
> +#define SYS_HDFGWTR_EL2 sys_reg(3, 4, 3, 1, 5)
> +#define SYS_HAFGRTR_EL2 sys_reg(3, 4, 3, 1, 6)
> #define SYS_SPSR_EL2 sys_reg(3, 4, 4, 0, 0)
> #define SYS_ELR_EL2 sys_reg(3, 4, 4, 0, 1)
> #define SYS_IFSR32_EL2 sys_reg(3, 4, 5, 0, 1)
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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