linux-kernel - Re: [PATCH v6 03/11] arm64: realm: Query IPA size from the RMM

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Message-ID: <e69536dd-aab2-49de-a026-506e09359207@arm.com>
Date: Tue, 15 Oct 2024 10:08:24 +0100
From: Steven Price <steven.price@....com>
To: Gavin Shan <gshan@...hat.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>,
 Suzuki K Poulose <suzuki.poulose@....com>, 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>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
 <alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v6 03/11] arm64: realm: Query IPA size from the RMM

On 15/10/2024 04:55, Gavin Shan wrote:
> On 10/5/24 12:42 AM, Steven Price wrote:
>> The top bit of the configured IPA size is used as an attribute to
>> control whether the address is protected or shared. Query the
>> configuration from the RMM to assertain which bit this is.
>>
>> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
>> Reviewed-by: Gavin Shan <gshan@...hat.com>
>> Co-developed-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>> Changes since v4:
>>   * Make PROT_NS_SHARED check is_realm_world() to reduce impact on
>>     non-CCA systems.
>> Changes since v2:
>>   * Drop unneeded extra brackets from PROT_NS_SHARED.
>>   * Drop the explicit alignment from 'config' as struct realm_config now
>>     specifies the alignment.
>> ---
>>   arch/arm64/include/asm/pgtable-prot.h | 4 ++++
>>   arch/arm64/include/asm/rsi.h          | 2 +-
>>   arch/arm64/kernel/rsi.c               | 8 ++++++++
>>   3 files changed, 13 insertions(+), 1 deletion(-)
>>
> 
> [...]
> 
>> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
>> index 9bf757b4b00c..a6495a64d9bb 100644
>> --- a/arch/arm64/kernel/rsi.c
>> +++ b/arch/arm64/kernel/rsi.c
>> @@ -8,6 +8,11 @@
>>   #include <linux/psci.h>
>>   #include <asm/rsi.h>
>>   +struct realm_config config;
>> +
> 
> Nit: I think this variable is file-scoped since it has a generic name.
> In this case, 'static' is needed to match with the scope.

Good spot - it should definitely be static.

Thanks,
Steve

>> +unsigned long prot_ns_shared;
>> +EXPORT_SYMBOL(prot_ns_shared);
>> +
>>   DEFINE_STATIC_KEY_FALSE_RO(rsi_present);
>>   EXPORT_SYMBOL(rsi_present);
>>   @@ -67,6 +72,9 @@ void __init arm64_rsi_init(void)
>>           return;
>>       if (!rsi_version_matches())
>>           return;
>> +    if (WARN_ON(rsi_get_realm_config(&config)))
>> +        return;
>> +    prot_ns_shared = BIT(config.ipa_bits - 1);
>>         arm64_rsi_setup_memory();
>>   
> 
> Thanks,
> Gavin
>