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From: Linu Cherian <linu.cherian@arm.com>
To: Mostafa Saleh <smostafa@google.com>
Cc: linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, maz@kernel.org,
	oupton@kernel.org, seiden@linux.ibm.com, joey.gouly@arm.com,
	suzuki.poulose@arm.com, yuzenghui@huawei.com,
	catalin.marinas@arm.com, will@kernel.org, vdonnefort@google.com,
	tabba@google.com, sebastianene@google.com, keirf@google.com
Subject: Re: [RFC PATCH v2 0/2] KVM: arm64: Add support for BBM level 3
Date: Thu, 30 Jul 2026 08:52:37 +0530	[thread overview]
Message-ID: <amrDfR-6q3xAAkTq@a079125.arm.com> (raw)
In-Reply-To: <20260723182140.4025575-1-smostafa@google.com>

Hi,

On Thu, Jul 23, 2026 at 06:21:38PM +0000, Mostafa Saleh wrote:
> This patch series adds support for BBM level 3 to KVM pgtable, it
> depends on [1]
> 
> Changes from v1:
> https://lore.kernel.org/all/20260717130901.2239134-1-smostafa@google.com/
> - Limit BBML3 to systems with FWB and DIC and remove race check.
> 
> Motivation
> ==========
> I have been looking into this for the context of:
> - Page table sharing between the host CPU stage-2 and the SMMUv3 for
>   protected KVM.
> - Use the pagtable code to populate SMMUv3 stage-2 shadowed
>   page table [2]
> 
> However, BBM level 3 is still useful for CPU only operations as it
> avoids intermediately breaking translation.
> 
> Design
> ======
> Some of the conditions that BBM level 3 will be useful in (RWHZWS):
> 1) A change to a PTE memory type, shareability, cacheability or OA

Could you please clarify how BBM level 3 is helping this particular scenario ?
This is supposed to be a case where break before make is required.

Thanks,
Linu Cherian.
 


  parent reply	other threads:[~2026-07-30  3:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-23 18:21 [RFC PATCH v2 0/2] KVM: arm64: Add support for BBM level 3 Mostafa Saleh
2026-07-23 18:21 ` [RFC PATCH v2 1/2] KVM: arm64: Add stage2_clean_old_pte() Mostafa Saleh
2026-07-23 18:21 ` [RFC PATCH v2 2/2] KVM: arm64: Support BBM level 3 Mostafa Saleh
2026-07-23 18:43   ` sashiko-bot
2026-07-24  8:17     ` Mostafa Saleh
2026-07-30  3:22 ` Linu Cherian [this message]
2026-07-30  9:30   ` [RFC PATCH v2 0/2] KVM: arm64: Add support for " Mostafa Saleh

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