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 15:55:22 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Michael Kelley <mhklinux@...look.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

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)
+


Suzuki