[PATCH v2 7/8] arm64: allow ID map to be extended to 52 bits

[Suzuki K Poulose]

On 22/12/17 15:23, Catalin Marinas wrote:
> From: Kristina Martsenko <kristina.martsenko at arm.com>
> 
> Currently, when using VA_BITS < 48, if the ID map text happens to be
> placed in physical memory above VA_BITS, we increase the VA size (up to
> 48) and create a new table level, in order to map in the ID map text.
> This is okay because the system always supports 48 bits of VA.
> 
> This patch extends the code such that if the system supports 52 bits of
> VA, and the ID map text is placed that high up, then we increase the VA
> size accordingly, up to 52.
> 
> One difference from the current implementation is that so far the
> condition of VA_BITS < 48 has meant that the top level table is always
> "full", with the maximum number of entries, and an extra table level is
> always needed. Now, when VA_BITS = 48 (and using 64k pages), the top
> level table is not full, and we simply need to increase the number of
> entries in it, instead of creating a new table level.
> 
> Tested-by: Bob Picco <bob.picco at oracle.com>
> Reviewed-by: Bob Picco <bob.picco at oracle.com>
> Signed-off-by: Kristina Martsenko <kristina.martsenko at arm.com>
> [catalin.marinas at arm.com: reduce arguments to __create_hyp_mappings()]
> [catalin.marinas at arm.com: reworked/renamed __cpu_uses_extended_idmap_level()]
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> ---
>   arch/arm/include/asm/kvm_mmu.h       |  5 +++
>   arch/arm64/include/asm/assembler.h   |  2 -
>   arch/arm64/include/asm/kvm_mmu.h     |  7 +++-
>   arch/arm64/include/asm/mmu_context.h | 18 +++++++--
>   arch/arm64/kernel/head.S             | 76 +++++++++++++++++++++---------------
>   arch/arm64/kvm/hyp-init.S            | 17 ++++----
>   arch/arm64/mm/mmu.c                  |  1 +
>   virt/kvm/arm/mmu.c                   | 10 ++++-
>   8 files changed, 87 insertions(+), 49 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 8dbec683638b..8c5643e2eea4 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -211,6 +211,11 @@ static inline bool __kvm_cpu_uses_extended_idmap(void)
>   	return false;
>   }
>   
> +static inline unsigned long __kvm_idmap_ptrs_per_pgd(void)
> +{
> +	return PTRS_PER_PGD;
> +}
> +
>   static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd,
>   				       pgd_t *hyp_pgd,
>   				       pgd_t *merged_hyp_pgd,
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 49ea3def4bd1..942fdb5ef0ad 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -344,10 +344,8 @@ alternative_endif
>    * tcr_set_idmap_t0sz - update TCR.T0SZ so that we can load the ID map
>    */
>   	.macro	tcr_set_idmap_t0sz, valreg, tmpreg
> -#ifndef CONFIG_ARM64_VA_BITS_48
>   	ldr_l	\tmpreg, idmap_t0sz
>   	bfi	\valreg, \tmpreg, #TCR_T0SZ_OFFSET, #TCR_TxSZ_WIDTH
> -#endif
>   	.endm
>   
>   /*
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index b3f7b68b042d..8d663ca0d50c 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -273,7 +273,12 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled);
>   
>   static inline bool __kvm_cpu_uses_extended_idmap(void)
>   {
> -	return __cpu_uses_extended_idmap();
> +	return __cpu_uses_extended_idmap_table();
> +}
> +
> +static inline unsigned long __kvm_idmap_ptrs_per_pgd(void)
> +{
> +	return idmap_ptrs_per_pgd;
>   }
>   
>   /*
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index accc2ff32a0e..7991718890c6 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -63,11 +63,21 @@ static inline void cpu_set_reserved_ttbr0(void)
>    * physical memory, in which case it will be smaller.
>    */
>   extern u64 idmap_t0sz;
> +extern u64 idmap_ptrs_per_pgd;
>   
> -static inline bool __cpu_uses_extended_idmap(void)
> +static inline bool __cpu_uses_extended_idmap_level(void)
>   {
> -	return (!IS_ENABLED(CONFIG_ARM64_VA_BITS_48) &&
> -		unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS)));
> +	return ARM64_HW_PGTABLE_LEVELS((64 - idmap_t0sz)) > CONFIG_PGTABLE_LEVELS;
> +}
> +
> +/*
> + * True if the extended ID map requires an extra level of translation table
> + * to be configured.
> + */
> +static inline bool __cpu_uses_extended_idmap_table(void)
> +{
> +	return __cpu_uses_extended_idmap_level() &&
> +		(idmap_ptrs_per_pgd == PTRS_PER_PGD);
>   }

As discussed offline, I was talking about changing

  __cpu_uses_extended_idmap_table =>  __cpu_uses_extended_idmap_level.

And the __cpu_uses_extended_idmap() doesn't need any changes. i.e :
It could look like :

static inline bool __cpu_uses_extended_idmap_level(void)
{
	return (!IS_ENABLED(CONFIG_ARM64_VA_BITS_48) &&
		unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS)));
}

static inline bool __cpu_uses_extended_idmap_level(void)
{
	return ARM64_HW_PGTABLE_LEVELS((64 - idmap_t0sz)) > CONFIG_PGTABLE_LEVELS;
}

And the __kvm_cpu_uses_extended_idmap() above should use the

__cpu_uses_extended_idmap_level().

Sorry for the confusion.


With that:

Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>