Re: [PATCH] arm64/mm: Fix __enable_mmu() for new TGRAN range values

From: Mark Rutland
Date: Fri Mar 05 2021 - 09:52:08 EST

On Fri, Mar 05, 2021 at 08:06:09PM +0530, Anshuman Khandual wrote:
> From: James Morse <james.morse@xxxxxxx>
>
> As per ARM ARM DDI 0487G.a, when FEAT_LPA2 is implemented, ID_AA64MMFR0_EL1
> might contain a range of values to describe supported translation granules
> (4K and 16K pages sizes in particular) instead of just enabled or disabled
> values. This changes __enable_mmu() function to handle complete acceptable
> range of values (depending on whether the field is signed or unsigned) now
> represented with ID_AA64MMFR0_TGRAN_SUPPORTED_[MIN..MAX] pair. While here,
> also fix similar situations in EFI stub and KVM as well.
>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: James Morse <james.morse@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
> Cc: linux-efi@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> arch/arm64/include/asm/sysreg.h | 20 ++++++++++++++------
> arch/arm64/kernel/head.S | 6 ++++--
> arch/arm64/kvm/reset.c | 23 ++++++++++++-----------
> drivers/firmware/efi/libstub/arm64-stub.c | 2 +-
> 4 files changed, 31 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index dfd4edb..d4a5fca9 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -796,6 +796,11 @@
> #define ID_AA64MMFR0_PARANGE_48 0x5
> #define ID_AA64MMFR0_PARANGE_52 0x6
>
> +#define ID_AA64MMFR0_TGRAN_2_SUPPORTED_DEFAULT 0x0
> +#define ID_AA64MMFR0_TGRAN_2_SUPPORTED_NONE 0x1
> +#define ID_AA64MMFR0_TGRAN_2_SUPPORTED_MIN 0x2
> +#define ID_AA64MMFR0_TGRAN_2_SUPPORTED_MAX 0x7

The TGRAN2 fields doesn't quite follow the usual ID scheme rules, so how
do we deteremine the max value? Does the ARM ARM say anything in
particular about them, like we do for some of the PMU ID fields?

Otherwise, this patch looks correct to me.

Thanks,
Mark.

> +
> #ifdef CONFIG_ARM64_PA_BITS_52
> #define ID_AA64MMFR0_PARANGE_MAX ID_AA64MMFR0_PARANGE_52
> #else
> @@ -961,14 +966,17 @@
> #define ID_PFR1_PROGMOD_SHIFT 0
>
> #if defined(CONFIG_ARM64_4K_PAGES)
> -#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN4_SHIFT
> -#define ID_AA64MMFR0_TGRAN_SUPPORTED ID_AA64MMFR0_TGRAN4_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN4_SHIFT
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MIN ID_AA64MMFR0_TGRAN4_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MAX 0x7
> #elif defined(CONFIG_ARM64_16K_PAGES)
> -#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN16_SHIFT
> -#define ID_AA64MMFR0_TGRAN_SUPPORTED ID_AA64MMFR0_TGRAN16_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN16_SHIFT
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MIN ID_AA64MMFR0_TGRAN16_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MAX 0xF
> #elif defined(CONFIG_ARM64_64K_PAGES)
> -#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN64_SHIFT
> -#define ID_AA64MMFR0_TGRAN_SUPPORTED ID_AA64MMFR0_TGRAN64_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SHIFT ID_AA64MMFR0_TGRAN64_SHIFT
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MIN ID_AA64MMFR0_TGRAN64_SUPPORTED
> +#define ID_AA64MMFR0_TGRAN_SUPPORTED_MAX 0x7
> #endif
>
> #define MVFR2_FPMISC_SHIFT 4
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 66b0e0b..8b469f1 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -655,8 +655,10 @@ SYM_FUNC_END(__secondary_too_slow)
> SYM_FUNC_START(__enable_mmu)
> mrs x2, ID_AA64MMFR0_EL1
> ubfx x2, x2, #ID_AA64MMFR0_TGRAN_SHIFT, 4
> - cmp x2, #ID_AA64MMFR0_TGRAN_SUPPORTED
> - b.ne __no_granule_support
> + cmp x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MIN
> + b.lt __no_granule_support
> + cmp x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
> + b.gt __no_granule_support
> update_early_cpu_boot_status 0, x2, x3
> adrp x2, idmap_pg_dir
> phys_to_ttbr x1, x1
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 47f3f03..fe72bfb 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -286,7 +286,7 @@ u32 get_kvm_ipa_limit(void)
>
> int kvm_set_ipa_limit(void)
> {
> - unsigned int parange, tgran_2;
> + unsigned int parange, tgran_2_shift, tgran_2;
> u64 mmfr0;
>
> mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
> @@ -300,27 +300,28 @@ int kvm_set_ipa_limit(void)
> switch (PAGE_SIZE) {
> default:
> case SZ_4K:
> - tgran_2 = ID_AA64MMFR0_TGRAN4_2_SHIFT;
> + tgran_2_shift = ID_AA64MMFR0_TGRAN4_2_SHIFT;
> break;
> case SZ_16K:
> - tgran_2 = ID_AA64MMFR0_TGRAN16_2_SHIFT;
> + tgran_2_shift = ID_AA64MMFR0_TGRAN16_2_SHIFT;
> break;
> case SZ_64K:
> - tgran_2 = ID_AA64MMFR0_TGRAN64_2_SHIFT;
> + tgran_2_shift = ID_AA64MMFR0_TGRAN64_2_SHIFT;
> break;
> }
>
> - switch (cpuid_feature_extract_unsigned_field(mmfr0, tgran_2)) {
> - default:
> - case 1:
> + tgran_2 = cpuid_feature_extract_unsigned_field(mmfr0, tgran_2_shift);
> + if (tgran_2 == ID_AA64MMFR0_TGRAN_2_SUPPORTED_NONE) {
> kvm_err("PAGE_SIZE not supported at Stage-2, giving up\n");
> return -EINVAL;
> - case 0:
> + } else if (tgran_2 == ID_AA64MMFR0_TGRAN_2_SUPPORTED_DEFAULT) {
> kvm_debug("PAGE_SIZE supported at Stage-2 (default)\n");
> - break;
> - case 2:
> + } else if (tgran_2 >= ID_AA64MMFR0_TGRAN_2_SUPPORTED_MIN &&
> + tgran_2 <= ID_AA64MMFR0_TGRAN_2_SUPPORTED_MAX) {
> kvm_debug("PAGE_SIZE supported at Stage-2 (advertised)\n");
> - break;
> + } else {
> + kvm_err("Unsupported value, giving up\n");
> + return -EINVAL;
> }
>
> kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> index b69d631..7bf0a7a 100644
> --- a/drivers/firmware/efi/libstub/arm64-stub.c
> +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> @@ -24,7 +24,7 @@ efi_status_t check_platform_features(void)
> return EFI_SUCCESS;
>
> tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
> - if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
> + if (tg < ID_AA64MMFR0_TGRAN_SUPPORTED_MIN || tg > ID_AA64MMFR0_TGRAN_SUPPORTED_MAX) {
> if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
> efi_err("This 64 KB granular kernel is not supported by your CPU\n");
> else
> --
> 2.7.4
>