Re: [PATCH v4 03/21] KVM: arm64: Add support for creating kernel-agnostic stage-1 page tables

[Gavin Shan <gshan@redhat.com>]

On 9/8/20 1:23 AM, Will Deacon wrote:
> The generic page-table walker is pretty useless as it stands, because it
> doesn't understand enough to allocate anything. Teach it about stage-1
> page-tables, and hook up an API for allocating these for the hypervisor
> at EL2.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Quentin Perret <qperret@google.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---

Reviewed-by: Gavin Shan <gshan@redhat.com>

>   arch/arm64/include/asm/kvm_pgtable.h |  36 ++++++++
>   arch/arm64/kvm/hyp/pgtable.c         | 133 +++++++++++++++++++++++++++
>   2 files changed, 169 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> index 1c5d981e15c3..91e364804547 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -77,6 +77,42 @@ struct kvm_pgtable_walker {
>   	const enum kvm_pgtable_walk_flags	flags;
>   };
>   
> +/**
> + * kvm_pgtable_hyp_init() - Initialise a hypervisor stage-1 page-table.
> + * @pgt:	Uninitialised page-table structure to initialise.
> + * @va_bits:	Maximum virtual address bits.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits);
> +
> +/**
> + * kvm_pgtable_hyp_destroy() - Destroy an unused hypervisor stage-1 page-table.
> + * @pgt:	Page-table structure initialised by kvm_pgtable_hyp_init().
> + *
> + * The page-table is assumed to be unreachable by any hardware walkers prior
> + * to freeing and therefore no TLB invalidation is performed.
> + */
> +void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt);
> +
> +/**
> + * kvm_pgtable_hyp_map() - Install a mapping in a hypervisor stage-1 page-table.
> + * @pgt:	Page-table structure initialised by kvm_pgtable_hyp_init().
> + * @addr:	Virtual address at which to place the mapping.
> + * @size:	Size of the mapping.
> + * @phys:	Physical address of the memory to map.
> + * @prot:	Permissions and attributes for the mapping.
> + *
> + * If device attributes are not explicitly requested in @prot, then the
> + * mapping will be normal, cacheable. Attempts to install a mapping for
> + * a virtual address that is already mapped will be rejected with an error
> + * and a WARN().
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
> +			enum kvm_pgtable_prot prot);
> +
>   /**
>    * kvm_pgtable_walk() - Walk a page-table.
>    * @pgt:	Page-table structure initialised by kvm_pgtable_*_init().
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 3fb9d1949a3f..23a1006aa4ef 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -24,8 +24,18 @@
>   
>   #define KVM_PTE_LEAF_ATTR_LO		GENMASK(11, 2)
>   
> +#define KVM_PTE_LEAF_ATTR_LO_S1_ATTRIDX	GENMASK(4, 2)
> +#define KVM_PTE_LEAF_ATTR_LO_S1_AP	GENMASK(7, 6)
> +#define KVM_PTE_LEAF_ATTR_LO_S1_AP_RO	3
> +#define KVM_PTE_LEAF_ATTR_LO_S1_AP_RW	1
> +#define KVM_PTE_LEAF_ATTR_LO_S1_SH	GENMASK(9, 8)
> +#define KVM_PTE_LEAF_ATTR_LO_S1_SH_IS	3
> +#define KVM_PTE_LEAF_ATTR_LO_S1_AF	BIT(10)
> +
>   #define KVM_PTE_LEAF_ATTR_HI		GENMASK(63, 51)
>   
> +#define KVM_PTE_LEAF_ATTR_HI_S1_XN	BIT(54)
> +
>   struct kvm_pgtable_walk_data {
>   	struct kvm_pgtable		*pgt;
>   	struct kvm_pgtable_walker	*walker;
> @@ -283,3 +293,126 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
>   
>   	return _kvm_pgtable_walk(&walk_data);
>   }
> +
> +struct hyp_map_data {
> +	u64		phys;
> +	kvm_pte_t	attr;
> +};
> +
> +static int hyp_map_set_prot_attr(enum kvm_pgtable_prot prot,
> +				 struct hyp_map_data *data)
> +{
> +	bool device = prot & KVM_PGTABLE_PROT_DEVICE;
> +	u32 mtype = device ? MT_DEVICE_nGnRE : MT_NORMAL;
> +	kvm_pte_t attr = FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_ATTRIDX, mtype);
> +	u32 sh = KVM_PTE_LEAF_ATTR_LO_S1_SH_IS;
> +	u32 ap = (prot & KVM_PGTABLE_PROT_W) ? KVM_PTE_LEAF_ATTR_LO_S1_AP_RW :
> +					       KVM_PTE_LEAF_ATTR_LO_S1_AP_RO;
> +
> +	if (!(prot & KVM_PGTABLE_PROT_R))
> +		return -EINVAL;
> +
> +	if (prot & KVM_PGTABLE_PROT_X) {
> +		if (prot & KVM_PGTABLE_PROT_W)
> +			return -EINVAL;
> +
> +		if (device)
> +			return -EINVAL;
> +	} else {
> +		attr |= KVM_PTE_LEAF_ATTR_HI_S1_XN;
> +	}
> +
> +	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_AP, ap);
> +	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_SH, sh);
> +	attr |= KVM_PTE_LEAF_ATTR_LO_S1_AF;
> +	data->attr = attr;
> +	return 0;
> +}
> +
> +static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
> +				    kvm_pte_t *ptep, struct hyp_map_data *data)
> +{
> +	u64 granule = kvm_granule_size(level), phys = data->phys;
> +
> +	if (!kvm_block_mapping_supported(addr, end, phys, level))
> +		return false;
> +
> +	WARN_ON(!kvm_set_valid_leaf_pte(ptep, phys, data->attr, level));
> +	data->phys += granule;
> +	return true;
> +}
> +
> +static int hyp_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
> +			  enum kvm_pgtable_walk_flags flag, void * const arg)
> +{
> +	kvm_pte_t *childp;
> +
> +	if (hyp_map_walker_try_leaf(addr, end, level, ptep, arg))
> +		return 0;
> +
> +	if (WARN_ON(level == KVM_PGTABLE_MAX_LEVELS - 1))
> +		return -EINVAL;
> +
> +	childp = (kvm_pte_t *)get_zeroed_page(GFP_KERNEL);
> +	if (!childp)
> +		return -ENOMEM;
> +
> +	kvm_set_table_pte(ptep, childp);
> +	return 0;
> +}
> +
> +int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
> +			enum kvm_pgtable_prot prot)
> +{
> +	int ret;
> +	struct hyp_map_data map_data = {
> +		.phys	= ALIGN_DOWN(phys, PAGE_SIZE),
> +	};
> +	struct kvm_pgtable_walker walker = {
> +		.cb	= hyp_map_walker,
> +		.flags	= KVM_PGTABLE_WALK_LEAF,
> +		.arg	= &map_data,
> +	};
> +
> +	ret = hyp_map_set_prot_attr(prot, &map_data);
> +	if (ret)
> +		return ret;
> +
> +	ret = kvm_pgtable_walk(pgt, addr, size, &walker);
> +	dsb(ishst);
> +	isb();
> +	return ret;
> +}
> +
> +int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits)
> +{
> +	u64 levels = ARM64_HW_PGTABLE_LEVELS(va_bits);
> +
> +	pgt->pgd = (kvm_pte_t *)get_zeroed_page(GFP_KERNEL);
> +	if (!pgt->pgd)
> +		return -ENOMEM;
> +
> +	pgt->ia_bits		= va_bits;
> +	pgt->start_level	= KVM_PGTABLE_MAX_LEVELS - levels;
> +	pgt->mmu		= NULL;
> +	return 0;
> +}
> +
> +static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
> +			   enum kvm_pgtable_walk_flags flag, void * const arg)
> +{
> +	free_page((unsigned long)kvm_pte_follow(*ptep));
> +	return 0;
> +}
> +
> +void kvm_pgtable_hyp_destroy(struct kvm_pgtable *pgt)
> +{
> +	struct kvm_pgtable_walker walker = {
> +		.cb	= hyp_free_walker,
> +		.flags	= KVM_PGTABLE_WALK_TABLE_POST,
> +	};
> +
> +	WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
> +	free_page((unsigned long)pgt->pgd);
> +	pgt->pgd = NULL;
> +}
> 


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel