From: Steffen Eiden <seiden@linux.ibm.com>
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>,
Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>,
Fuad Tabba <fuad.tabba@linux.dev>,
Joey Gouly <joey.gouly@arm.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 03/12] KVM: arm64: Hide TLBID from guest sysregs
Date: Mon, 12 Oct 2026 10:12:54 +0200 [thread overview]
Message-ID: <20261012081254.483793-A-seiden@linux.ibm.com> (raw)
In-Reply-To: <20261001110655.461473-4-kristina.martsenko@arm.com>
On Thu, Oct 01, 2026 at 12:06:46PM +0100, Kristina Martšenko wrote:
> Don't expose FEAT_TLBID to guests. It wouldn't be useful in the general
> case since a guest doesn't know which domains exist and its vCPUs can be
> moved between any physical CPUs.
>
> Try to hide TLBID sysregs and sysreg fields from the guest:
>
> * Report the feature as not supported in the ID register
> ID_AA64MMFR4_EL1.TLBID.
>
> * Configure the TLBIDIDR_EL1 sysreg to UNDEF via the FGU mechanism.
> Sanitize a nested hypervisor's HFGRTR2.nTLBIDIDR.
>
> * Sanitize a nested hypervisor's HCRX.{VTLBIDEn,VTLBIDOSEn,FNB}.
>
> * VTLBID{OS}<n>_EL2 registers are VNCR-backed and not exposed to
> guests (apart from being able to read/write into the VNCR page) so
> no need to handle them in sys_reg_descs or elsewhere.
>
> * The guest is free to set SCTLR2_EL{1,2}.TLBOSNIS, which shouldn't
> matter to KVM.
>
What confuse me where a bit that you wrote 'try to hide'.
For me this indicates that the hiding process may not be successful.
For me the code looks like it will always succeddin hiding the feature
from the guest, no? Did I miss anything?
Same for the next patch.
Steffen
next prev parent reply other threads:[~2026-10-12 8:13 UTC|newest]
Thread overview: 21+ 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
2026-10-12 8:12 ` Steffen Eiden [this message]
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 ` [RFC 00/12] arm64: Add support for TLBI domains Marc Zyngier
2026-10-05 8:40 ` 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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