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From: Marc Zyngier <maz@kernel.org>
To: "Kristina Martšenko" <kristina.martsenko@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-efi@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	David Hildenbrand <david@kernel.org>,
	Lorenzo Stoakes <ljs@kernel.org>,
	Linu Cherian <linu.cherian@arm.com>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Hanjun Guo <guohanjun@huawei.com>,
	Sudeep Holla <sudeep.holla@kernel.org>,
	Oliver Upton <oupton@kernel.org>,
	Fuad Tabba <fuad.tabba@linux.dev>,
	Joey Gouly <joey.gouly@arm.com>,
	Steffen Eiden <seiden@linux.ibm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>
Subject: Re: [RFC 00/12] arm64: Add support for TLBI domains
Date: Sat, 03 Oct 2026 17:12:50 +0100	[thread overview]
Message-ID: <87mrsu3gql.wl-maz@kernel.org> (raw)
In-Reply-To: <20261001110655.461473-1-kristina.martsenko@arm.com>

Hi Kristina,

On Thu, 01 Oct 2026 12:06:43 +0100,
Kristina Martšenko <kristina.martsenko@arm.com> wrote:

[...]

>   * It's also possible to use TLBI domains to limit a KVM guest's TLB
>     invalidations to CPUs where the guest has run. I'll try to include that in
>     the next version. This series only disables domains for guests.

My take on this is that just like MPAM, it makes little sense to
expose this to guests. As long as the L0 hypervisor has the means that
to scope TLBIs to the relevant domains (subset of CPUs to start with,
but hopefully SMMUs eventually), we're good.

>   * With this series a long-running process may eventually run on all CPUs and
>     just issue broadcast TLBIs. It may be worth periodically reducing the set
>     of CPUs but it's not clear when.

I had a think about that some time ago, and thought that you were sure
to be sub-optimal when the number of CPUs you have run on is greater
than the number of threads in your process.

But I'm sure there are better heuristics! ;-)

Thanks,

	M.

-- 
Jazz isn't dead. It just smells funny.


  parent reply	other threads:[~2026-10-03 16:09 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-01 11:06 [RFC 00/12] arm64: Add support for TLBI domains Kristina Martšenko
2026-10-01 11:06 ` [RFC 01/12] arm64: sysreg: Add definitions for FEAT_TLBID Kristina Martšenko
2026-10-01 11:06 ` [RFC 02/12] arm64: Detect FEAT_TLBID Kristina Martšenko
2026-10-01 11:06 ` [RFC 03/12] KVM: arm64: Hide TLBID from guest sysregs Kristina Martšenko
2026-10-01 11:06 ` [RFC 04/12] KVM: arm64: Hide TLBID from guest instructions Kristina Martšenko
2026-10-01 11:06 ` [RFC 05/12] ACPICA: Add TLBI table definition Kristina Martšenko
2026-10-01 11:06 ` [RFC 06/12] ACPI: TLBI: Parse domains from table Kristina Martšenko
2026-10-01 11:06 ` [RFC 07/12] arm64: tlbid: Set up CPU domain bitmaps Kristina Martšenko
2026-10-01 11:06 ` [RFC 08/12] efi/arm: Check return value of init_new_context() Kristina Martšenko
2026-10-04  8:00   ` Ard Biesheuvel
2026-10-01 11:06 ` [RFC 09/12] arm64: tlbid: Track the TLBI domain of a task Kristina Martšenko
2026-10-01 11:06 ` [RFC 10/12] arm64: Support TLBIP instructions Kristina Martšenko
2026-10-01 11:06 ` [RFC 11/12] arm64: tlbid: Pass domain to TLBI instructions Kristina Martšenko
2026-10-01 11:06 ` [RFC 12/12] arm64: tlbid: Add documentation Kristina Martšenko
2026-10-03 16:12 ` Marc Zyngier [this message]
2026-10-05  8:40   ` [RFC 00/12] arm64: Add support for TLBI domains Oliver Upton
2026-10-04 18:06 ` Zi Yan
2026-10-05  6:29   ` Will Deacon
2026-10-05 18:13     ` Zi Yan
2026-10-05 11:07   ` Catalin Marinas

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