linux-kernel - Re: [PATCH v6 11/43] arm64: RME: RTT tear down

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Message-ID: <dcb08082-4048-4573-9dd4-bf3b81a06bb9@redhat.com>
Date: Thu, 30 Jan 2025 09:06:47 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....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 11/43] arm64: RME: RTT tear down

On 12/13/24 1:55 AM, Steven Price wrote:
> The RMM owns the stage 2 page tables for a realm, and KVM must request
> that the RMM creates/destroys entries as necessary. The physical pages
> to store the page tables are delegated to the realm as required, and can
> be undelegated when no longer used.
> 
> Creating new RTTs is the easy part, tearing down is a little more
> tricky. The result of realm_rtt_destroy() can be used to effectively
> walk the tree and destroy the entries (undelegating pages that were
> given to the realm).
> 
> Signed-off-by: Steven Price <steven.price@....com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes since v5:
>   * Rename some RME_xxx defines to do with page sizes as RMM_xxx - they are
>     a property of the RMM specification not the RME architecture.
> Changes since v2:
>   * Moved {alloc,free}_delegated_page() and ensure_spare_page() to a
>     later patch when they are actually used.
>   * Some simplifications now rmi_xxx() functions allow NULL as an output
>     parameter.
>   * Improved comments and code layout.
> ---
>   arch/arm64/include/asm/kvm_rme.h |  19 ++++++
>   arch/arm64/kvm/mmu.c             |   6 +-
>   arch/arm64/kvm/rme.c             | 112 +++++++++++++++++++++++++++++++
>   3 files changed, 134 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
> index 209cd99f03dd..32bdedf1d866 100644
> --- a/arch/arm64/include/asm/kvm_rme.h
> +++ b/arch/arm64/include/asm/kvm_rme.h
> @@ -71,5 +71,24 @@ u32 kvm_realm_ipa_limit(void);
>   int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
>   int kvm_init_realm_vm(struct kvm *kvm);
>   void kvm_destroy_realm(struct kvm *kvm);
> +void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits);
> +
> +#define RMM_RTT_BLOCK_LEVEL	2
> +#define RMM_RTT_MAX_LEVEL	3
> +
> +#define RMM_PAGE_SHIFT		12
> +#define RMM_PAGE_SIZE		BIT(RMM_PAGE_SHIFT)
> +/* See ARM64_HW_PGTABLE_LEVEL_SHIFT() */
> +#define RMM_RTT_LEVEL_SHIFT(l)	\
> +	((RMM_PAGE_SHIFT - 3) * (4 - (l)) + 3)
> +#define RMM_L2_BLOCK_SIZE	BIT(RMM_RTT_LEVEL_SHIFT(2))
> +
> +static inline unsigned long rme_rtt_level_mapsize(int level)
> +{
> +	if (WARN_ON(level > RMM_RTT_MAX_LEVEL))
> +		return RMM_PAGE_SIZE;
> +
> +	return (1UL << RMM_RTT_LEVEL_SHIFT(level));
> +}
>   
>   #endif

All those definitions can be moved to rme.c since they're only used in rme.c

Thanks,
Gavin