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Date: Thu, 19 Jun 2025 20:47:18 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: =?utf-8?Q?Miko=C5=82aj?= Lenczewski <miko.lenczewski@arm.com>
Cc: ryan.roberts@arm.com, yang@os.amperecomputing.com, will@kernel.org,
	jean-philippe@linaro.org, robin.murphy@arm.com, joro@8bytes.org,
	maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com,
	james.morse@arm.com, broonie@kernel.org, ardb@kernel.org,
	baohua@kernel.org, suzuki.poulose@arm.com, david@redhat.com,
	jgg@ziepe.ca, nicolinc@nvidia.com, jsnitsel@redhat.com,
	mshavit@google.com, kevin.tian@intel.com,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux.dev
Subject: Re: [PATCH v7 4/4] arm64/mm: Elide tlbi in contpte_convert() under
 BBML2
Message-ID: <aFRpRnXi3tP_iHEJ@arm.com>
References: <20250617095104.6772-1-miko.lenczewski@arm.com>
 <20250617095104.6772-5-miko.lenczewski@arm.com>
 <aFRlDSZ2PPnHixjc@arm.com>
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In-Reply-To: <aFRlDSZ2PPnHixjc@arm.com>

On Thu, Jun 19, 2025 at 08:29:24PM +0100, Catalin Marinas wrote:
> On Tue, Jun 17, 2025 at 09:51:04AM +0000, Mikołaj Lenczewski wrote:
> > +	if (!system_supports_bbml2_noabort())
> > +		__flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3);
> >  
> >  	__set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES);
> 
> Eliding the TLBI here is all good but looking at the overall set_ptes(),
> why do we bother with unfold+fold for BBML2? Can we not just change
> them in place without going through __ptep_get_and_clear()?

Ah, it's unlikely that we'd be able to fold them back if only one pte in
the range was modified, so this optimisation would very rarely/never
trigger. So, for this patch:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>