linux-kernel - Re: [PATCH v5 09/43] arm64: RME: ioctls to create and configure realms

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Message-ID: <a5967441-0ea7-4c17-a87b-3f95c0ef0642@arm.com>
Date: Fri, 1 Nov 2024 16:22:46 +0000
From: Steven Price <steven.price@....com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>, 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>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>
Subject: Re: [PATCH v5 09/43] arm64: RME: ioctls to create and configure
 realms

On 30/10/2024 07:55, Aneesh Kumar K.V wrote:
> Steven Price <steven.price@....com> writes:
> 
>> +
>> +out_undelegate_tables:
>> +	while (--i >= 0) {
>> +		phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i * PAGE_SIZE;
>> +
>> +		WARN_ON(rmi_granule_undelegate(pgd_phys));
>> +	}
>> +	WARN_ON(rmi_granule_undelegate(rd_phys));
>> +free_rd:
>> +	free_page((unsigned long)rd);
>> +	return r;
>> +}
>> +
> 
> we should avoid that free_page on an undelegate failure? rd_phys we can
> handle here. Not sure how to handle the pgd_phys.

Good point. I think for pgd_phys setting kvm->arch.mmu.pgt=NULL should
be sufficient to prevent the pages being freed.

Thanks,
Steve