linux-kernel - RE: [PATCH v3 10/14] arm64: Force device mappings to be non-secure shared

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Date: Mon, 17 Jun 2024 03:33:41 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Steven Price <steven.price@....com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>
CC: Suzuki K Poulose <suzuki.poulose@....com>, Catalin Marinas
	<catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>, Will Deacon
	<will@...nel.org>, James Morse <james.morse@....com>, Oliver Upton
	<oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Joey Gouly <joey.gouly@....com>, Alexandru
 Elisei <alexandru.elisei@....com>, Christoffer Dall
	<christoffer.dall@....com>, Fuad Tabba <tabba@...gle.com>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>, Ganapatrao
 Kulkarni <gankulkarni@...amperecomputing.com>
Subject: RE: [PATCH v3 10/14] arm64: Force device mappings to be non-secure
 shared

From: Steven Price <steven.price@....com> Sent: Wednesday, June 5, 2024 2:30 AM
> 
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Device mappings (currently) need to be emulated by the VMM so must be
> mapped shared with the host.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>  arch/arm64/include/asm/pgtable.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 11d614d83317..c986fde262c0 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -644,7 +644,7 @@ static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
>  #define pgprot_writecombine(prot) \
>  	__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)
> +	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_PXN | PTE_UXN | PROT_NS_SHARED)
>  #define pgprot_tagged(prot) \
>  	__pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_TAGGED))
>  #define pgprot_mhp	pgprot_tagged

In v2 of the patches, Catalin raised a question about the need for
pgprot_decrypted(). What was concluded? It still looks to me like
pgprot_decrypted() and prot_encrypted() are needed, by
dma_direct_mmap() and remap_oldmem_pfn_range(), respectively.
Also, assuming Hyper-V supports CCA at some point, the Linux guest
drivers for Hyper-V need pgprot_decrypted() in hv_ringbuffer_init().

Michael