Re: [PATCH] arm64: mte: Map hotplugged memory as Normal Tagged

[David Hildenbrand <david@redhat.com>]

On 09.03.21 13:26, Catalin Marinas wrote:
> In a system supporting MTE, the linear map must allow reading/writing
> allocation tags by setting the memory type as Normal Tagged. Currently,
> this is only handled for memory present at boot. Hotplugged memory uses
> Normal non-Tagged memory.
> 
> Introduce pgprot_mhp() for hotplugged memory and use it in
> add_memory_resource(). The arm64 code maps pgprot_mhp() to
> pgprot_tagged().
> 
> Note that ZONE_DEVICE memory should not be mapped as Tagged and
> therefore setting the memory type in arch_add_memory() is not feasible.
> 
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Fixes: 0178dc761368 ("arm64: mte: Use Normal Tagged attributes for the linear map")
> Reported-by: Patrick Daly <pdaly@codeaurora.org>
> Link: https://lore.kernel.org/r/1614745263-27827-1-git-send-email-pdaly@codeaurora.org
> Cc: <stable@vger.kernel.org> # 5.10.x
> Cc: Will Deacon <will@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Cc: David Hildenbrand <david@redhat.com>
> ---
> 
> Patrick, could you please give this patch a try on your platform? Thanks.
> 
>   arch/arm64/include/asm/pgtable-prot.h | 1 -
>   arch/arm64/include/asm/pgtable.h      | 3 +++
>   arch/arm64/mm/mmu.c                   | 3 ++-
>   include/linux/pgtable.h               | 4 ++++
>   mm/memory_hotplug.c                   | 2 +-
>   5 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
> index 046be789fbb4..9a65fb528110 100644
> --- a/arch/arm64/include/asm/pgtable-prot.h
> +++ b/arch/arm64/include/asm/pgtable-prot.h
> @@ -66,7 +66,6 @@ extern bool arm64_use_ng_mappings;
>   #define _PAGE_DEFAULT		(_PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))
>   
>   #define PAGE_KERNEL		__pgprot(PROT_NORMAL)
> -#define PAGE_KERNEL_TAGGED	__pgprot(PROT_NORMAL_TAGGED)
>   #define PAGE_KERNEL_RO		__pgprot((PROT_NORMAL & ~PTE_WRITE) | PTE_RDONLY)
>   #define PAGE_KERNEL_ROX		__pgprot((PROT_NORMAL & ~(PTE_WRITE | PTE_PXN)) | PTE_RDONLY)
>   #define PAGE_KERNEL_EXEC	__pgprot(PROT_NORMAL & ~PTE_PXN)
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index e17b96d0e4b5..47027796c2f9 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -486,6 +486,9 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>   	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_NC) | PTE_PXN | PTE_UXN)
>   #define pgprot_device(prot) \
>   	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_PXN | PTE_UXN)
> +#define pgprot_tagged(prot) \
> +	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_TAGGED))
> +#define pgprot_mhp	pgprot_tagged
>   /*
>    * DMA allocations for non-coherent devices use what the Arm architecture calls
>    * "Normal non-cacheable" memory, which permits speculation, unaligned accesses
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 3802cfbdd20d..9c8aa1b44cd5 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -512,7 +512,8 @@ static void __init map_mem(pgd_t *pgdp)
>   		 * if MTE is present. Otherwise, it has the same attributes as
>   		 * PAGE_KERNEL.
>   		 */
> -		__map_memblock(pgdp, start, end, PAGE_KERNEL_TAGGED, flags);
> +		__map_memblock(pgdp, start, end, pgprot_tagged(PAGE_KERNEL),
> +			       flags);
>   	}
>   
>   	/*
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index cdfc4e9f253e..5e772392a379 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -904,6 +904,10 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
>   #define pgprot_device pgprot_noncached
>   #endif
>   
> +#ifndef pgprot_mhp
> +#define pgprot_mhp(prot)	(prot)
> +#endif
> +
>   #ifdef CONFIG_MMU
>   #ifndef pgprot_modify
>   #define pgprot_modify pgprot_modify
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 5ba51a8bdaeb..0cdbbfbc5757 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1072,7 +1072,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
>    */
>   int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
>   {
> -	struct mhp_params params = { .pgprot = PAGE_KERNEL };
> +	struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
>   	u64 start, size;
>   	bool new_node = false;
>   	int ret;
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb