linux-kernel - Re: [PATCH v4 21/43] arm64: RME: Runtime faulting of memory

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Message-ID: <20240904144821.GA223966@myrica>
Date: Wed, 4 Sep 2024 15:48:21 +0100
From: Jean-Philippe Brucker <jean-philippe@...aro.org>
To: Steven Price <steven.price@....com>
Cc: kvm@...r.kernel.org, kvmarm@...ts.linux.dev,
	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 v4 21/43] arm64: RME: Runtime faulting of memory

On Wed, Aug 21, 2024 at 04:38:22PM +0100, Steven Price wrote:
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index 2c4e28b457be..337b3dd1e00c 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -627,6 +627,181 @@ static int fold_rtt(struct realm *realm, unsigned long addr, int level)
>  	return 0;
>  }
>  
> +static phys_addr_t rtt_get_phys(struct realm *realm, struct rtt_entry *rtt)
> +{
> +	bool lpa2 = realm->params->flags & RMI_REALM_PARAM_FLAG_LPA2;

At this point realm->params is NULL, cleared by kvm_create_realm()

Thanks,
Jean

> +
> +	if (lpa2)
> +		return rtt->desc & GENMASK(49, 12);
> +	return rtt->desc & GENMASK(47, 12);
> +}
> +
> +int realm_map_protected(struct realm *realm,
> +			unsigned long base_ipa,
> +			struct page *dst_page,
> +			unsigned long map_size,
> +			struct kvm_mmu_memory_cache *memcache)
> +{
> +	phys_addr_t dst_phys = page_to_phys(dst_page);
> +	phys_addr_t rd = virt_to_phys(realm->rd);
> +	unsigned long phys = dst_phys;
> +	unsigned long ipa = base_ipa;
> +	unsigned long size;
> +	int map_level;
> +	int ret = 0;
> +
> +	if (WARN_ON(!IS_ALIGNED(ipa, map_size)))
> +		return -EINVAL;
> +
> +	switch (map_size) {
> +	case PAGE_SIZE:
> +		map_level = 3;
> +		break;
> +	case RME_L2_BLOCK_SIZE:
> +		map_level = 2;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	if (map_level < RME_RTT_MAX_LEVEL) {
> +		/*
> +		 * A temporary RTT is needed during the map, precreate it,
> +		 * however if there is an error (e.g. missing parent tables)
> +		 * this will be handled below.
> +		 */
> +		realm_create_rtt_levels(realm, ipa, map_level,
> +					RME_RTT_MAX_LEVEL, memcache);
> +	}
> +
> +	for (size = 0; size < map_size; size += PAGE_SIZE) {
> +		if (rmi_granule_delegate(phys)) {
> +			struct rtt_entry rtt;
> +
> +			/*
> +			 * It's possible we raced with another VCPU on the same
> +			 * fault. If the entry exists and matches then exit
> +			 * early and assume the other VCPU will handle the
> +			 * mapping.
> +			 */
> +			if (rmi_rtt_read_entry(rd, ipa, RME_RTT_MAX_LEVEL, &rtt))
> +				goto err;
> +
> +			/*
> +			 * FIXME: For a block mapping this could race at level
> +			 * 2 or 3... currently we don't support block mappings
> +			 */
> +			if (WARN_ON((rtt.walk_level != RME_RTT_MAX_LEVEL ||
> +				     rtt.state != RMI_ASSIGNED ||
> +				     rtt_get_phys(realm, &rtt) != phys))) {