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Date: Wed, 12 Jun 2024 11:59:22 +0100
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Subject: Re: [PATCH v3 02/14] arm64: Detect if in a realm and set RIPAS RAM
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To: Jean-Philippe Brucker <jean-philippe@linaro.org>,
 Steven Price <steven.price@arm.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev,
 Catalin Marinas <catalin.marinas@arm.com>, Marc Zyngier <maz@kernel.org>,
 Will Deacon <will@kernel.org>, James Morse <james.morse@arm.com>,
 Oliver Upton <oliver.upton@linux.dev>, Zenghui Yu <yuzenghui@huawei.com>,
 linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
 Joey Gouly <joey.gouly@arm.com>, Alexandru Elisei
 <alexandru.elisei@arm.com>, Christoffer Dall <christoffer.dall@arm.com>,
 Fuad Tabba <tabba@google.com>, linux-coco@lists.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
References: <20240605093006.145492-1-steven.price@arm.com>
 <20240605093006.145492-3-steven.price@arm.com> <20240612104023.GB4602@myrica>
From: Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <20240612104023.GB4602@myrica>
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On 12/06/2024 11:40, Jean-Philippe Brucker wrote:
> On Wed, Jun 05, 2024 at 10:29:54AM +0100, Steven Price wrote:
>> From: Suzuki K Poulose <suzuki.poulose@arm.com>
>>
>> Detect that the VM is a realm guest by the presence of the RSI
>> interface.
>>
>> If in a realm then all memory needs to be marked as RIPAS RAM initially,
>> the loader may or may not have done this for us. To be sure iterate over
>> all RAM and mark it as such. Any failure is fatal as that implies the
>> RAM regions passed to Linux are incorrect - which would mean failing
>> later when attempting to access non-existent RAM.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Co-developed-by: Steven Price <steven.price@arm.com>
>> Signed-off-by: Steven Price <steven.price@arm.com>
> 
>> +static bool rsi_version_matches(void)
>> +{
>> +	unsigned long ver_lower, ver_higher;
>> +	unsigned long ret = rsi_request_version(RSI_ABI_VERSION,
>> +						&ver_lower,
>> +						&ver_higher);
> 
> There is a regression on QEMU TCG (in emulation mode, not running under KVM):
> 
>    qemu-system-aarch64 -M virt -cpu max -kernel Image -nographic
> 
> This doesn't implement EL3 or EL2, so SMC is UNDEFINED (DDI0487J.a R_HMXQS),
> and we end up with an undef instruction exception. So this patch would
> also break hardware that only implements EL1 (I don't know if it exists).

Thanks for the report,  Could we not check ID_AA64PFR0_EL1.EL3 >= 0 ? I
think we do this for kvm-unit-tests, we need the same here.


Suzuki

> 
> The easiest fix is to detect the SMC conduit through the PSCI node in DT.
> SMCCC helpers already do this, but we can't use them this early in the
> boot. I tested adding an early probe to the PSCI driver to check this, see
> attached patches.
> 
> Note that we do need to test the conduit after finding a PSCI node,
> because even though it doesn't implement EL2 in this configuration, QEMU
> still accepts PSCI HVCs in order to support SMP.
> 
> Thanks,
> Jean
>