From: Marc Zyngier <maz@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Oliver Upton <oupton@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: Clear VTCR_EL2 in __init_el2_stage2()
Date: Fri, 13 Mar 2026 07:25:55 +0000 [thread overview]
Message-ID: <87sea4chrw.wl-maz@kernel.org> (raw)
In-Reply-To: <20260313053857.1277828-1-anshuman.khandual@arm.com>
On Fri, 13 Mar 2026 05:38:57 +0000,
Anshuman Khandual <anshuman.khandual@arm.com> wrote:
>
> Clear VTCR_EL2 along with VTTBR_EL2 register in __init_el2_stage2(), which
> ensures that MMU stage-2 translation remain disabled. Although clearing out
> VTTBR_EL2 probably should have been sufficient but adding VTCR_EL2 improves
> overall safety.
This serves no purpose whatsoever. Even the write to VTTBR_EL2 is
pointless, and writing 0 is no better than writing *any* other value.
The only thing that matters at this stage is HCR_EL2.VM, which
actually controls stage-2 translation (contrary to your above
assertion). This of course is not captured by this macro.
So what are you *really* trying to achieve?
Thanks,
M.
--
Jazz isn't dead. It just smells funny.
next prev parent reply other threads:[~2026-03-13 7:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-13 5:38 [PATCH] arm64: Clear VTCR_EL2 in __init_el2_stage2() Anshuman Khandual
2026-03-13 7:25 ` Marc Zyngier [this message]
2026-03-13 7:54 ` Anshuman Khandual
2026-03-13 8:07 ` Marc Zyngier
2026-03-13 8:11 ` Marc Zyngier
2026-03-13 8:39 ` Anshuman Khandual
2026-03-13 9:06 ` Marc Zyngier
2026-03-13 9:59 ` Mark Rutland
2026-03-17 2:46 ` Anshuman Khandual
2026-03-17 9:15 ` Marc Zyngier
2026-03-17 10:16 ` Mark Rutland
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