linux-kernel - Re: [PATCH v5 11/19] arm64: rsi: Map unprotected MMIO as decrypted

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Message-ID: <32159e6c-ad6a-4beb-b854-fbef9bdc9862@arm.com>
Date: Fri, 30 Aug 2024 16:54:47 +0100
From: Steven Price <steven.price@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>, kvm@...r.kernel.org,
 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-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,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>
Subject: Re: [PATCH v5 11/19] arm64: rsi: Map unprotected MMIO as decrypted

On 19/08/2024 15:11, Suzuki K Poulose wrote:
> Hi Steven
> 
> On 19/08/2024 14:19, Steven Price wrote:
>> From: Suzuki K Poulose <suzuki.poulose@....com>
>>
>> Instead of marking every MMIO as shared, check if the given region is
>> "Protected" and apply the permissions accordingly.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>> New patch for v5
>> ---
>>   arch/arm64/kernel/rsi.c | 15 +++++++++++++++
>>   arch/arm64/mm/mmu.c     |  2 +-
>>   2 files changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
>> index 381a5b9a5333..672dd6862298 100644
>> --- a/arch/arm64/kernel/rsi.c
>> +++ b/arch/arm64/kernel/rsi.c
>> @@ -6,6 +6,8 @@
>>   #include <linux/jump_label.h>
>>   #include <linux/memblock.h>
>>   #include <linux/psci.h>
>> +
>> +#include <asm/io.h>
>>   #include <asm/rsi.h>
>>     struct realm_config config;
>> @@ -93,6 +95,16 @@ bool arm64_rsi_is_protected_mmio(phys_addr_t base,
>> size_t size)
>>   }
>>   EXPORT_SYMBOL(arm64_rsi_is_protected_mmio);
>>   +static int realm_ioremap_hook(phys_addr_t phys, size_t size,
>> pgprot_t *prot)
>> +{
>> +    if (arm64_rsi_is_protected_mmio(phys, size))
>> +        *prot = pgprot_encrypted(*prot);
>> +    else
>> +        *prot = pgprot_decrypted(*prot);
>> +
>> +    return 0;
>> +}
>> +
>>   void __init arm64_rsi_init(void)
>>   {
>>       /*
>> @@ -107,6 +119,9 @@ void __init arm64_rsi_init(void)
>>           return;
>>       prot_ns_shared = BIT(config.ipa_bits - 1);
>>   +    if (arm64_ioremap_prot_hook_register(realm_ioremap_hook))
>> +        return;
>> +
>>       static_branch_enable(&rsi_present);
>>   }
>>   diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 06b66c23c124..0c2fa35beca0 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1207,7 +1207,7 @@ void set_fixmap_io(enum fixed_addresses idx,
>> phys_addr_t phys)
>>       else
>>           prot = pgprot_encrypted(prot);
>>   -    __set_fixmap(idx, phys, prot);
>> +    __set_fixmap(idx, phys & PAGE_MASK, prot);
> 
> This looks like it should be part of the previous patch ? Otherwise
> looks good to me.

Good spot - yes it should!

Thanks,
Steve