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 15:46:01 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Suzuki K Poulose <suzuki.poulose@....com>, Steven Price
	<steven.price@....com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>
CC: 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: Suzuki K Poulose <suzuki.poulose@....com> Sent: Monday, June 17, 2024 7:55 AM
> 
> On 17/06/2024 04:33, Michael Kelley wrote:
> > 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().
> 
> Right, I think we could simply do :
> 
> diff --git a/arch/arm64/include/asm/pgtable.h
> b/arch/arm64/include/asm/pgtable.h
> index c986fde262c0..1ed45893d1e6 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -648,6 +648,10 @@ static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
>   #define pgprot_tagged(prot) \
>          __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_TAGGED))
>   #define pgprot_mhp     pgprot_tagged
> +
> +#define pgprot_decrypted(prot) __pgprot_modify(prot, PROT_NS_SHARED, PROT_NS_SHARED)
> +#define pgprot_encrypted(prot)  __pgprot_modify(prot, PROT_NS_SHARED, 0)
> +
> 

Yes, looks right to me.

Michael