From: Marc Zyngier <maz@kernel.org>
To: Gyujeong Jin <wlsrbwjd7232@gmail.com>
Cc: oliver.upton@linux.dev, joey.gouly@arm.com,
suzuki.poulose@arm.com, yuzenghui@huawei.com,
catalin.marinas@arm.com, will@kernel.org, kvmarm@lists.linux.dev,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, gyutrange <wlsrbwjd643@naver.com>,
stable@vger.kernel.org, DongHa Lee <gap-dev@example.com>,
Daehyeon Ko <4ncient@example.com>,
Geonha Lee <leegn4a@example.com>,
Hyungyu Oh <dqpc_lover@example.com>,
Jaewon Yang <r4mbb1@example.com>
Subject: Re: [PATCH] KVM: arm64: nested: Fix VA sign extension in VNCR/TLBI paths
Date: Mon, 01 Sep 2025 15:26:06 +0100 [thread overview]
Message-ID: <86wm6ickqp.wl-maz@kernel.org> (raw)
In-Reply-To: <20250901141551.57981-1-wlsrbwjd7232@gmail.com>
On Mon, 01 Sep 2025 15:15:51 +0100,
Gyujeong Jin <wlsrbwjd7232@gmail.com> wrote:
>
> From: gyutrange <wlsrbwjd643@naver.com>
>
> VNCR/TLBI VA reconstruction currently uses bit 48 as the sign bit,
> but for 48-bit virtual addresses the correct sign bit is bit 47.
No, that's not the case. Bit 55 is used at all times to determine
which half of the address space a VA gets resolved from.
> Using 48 can mis-canonicalize addresses in the negative half and may
> cause missed invalidations.
>
> Although VNCR_EL2 encodes other architectural fields (RESS, BADDR;
> see Arm ARM D24.2.206), sign_extend64() interprets its second argument
> as the index of the sign bit. Passing 48 prevents propagation of the
> canonical sign bit for 48-bit VAs.
>
> Impact:
> - Incorrect canonicalization of VAs with bit47=1
No. We are not trying to make the VA canonical.
> - Potential stale VNCR pseudo-TLB entries after TLBI or MMU notifier
No. The pseudo TLB is never created the first place.
> - Possible incorrect translation/permissions or DoS when combined
> with other issues
Please explain, as "other issues" is not a valid argument.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2025-09-01 14:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-01 14:15 [PATCH] KVM: arm64: nested: Fix VA sign extension in VNCR/TLBI paths Gyujeong Jin
2025-09-01 14:26 ` Marc Zyngier [this message]
2025-09-01 20:03 ` Greg KH
2025-09-01 20:04 ` Greg KH
-- strict thread matches above, loose matches on Subject: below --
2025-09-01 12:45 Gyujeong Jin
2025-09-01 13:28 ` Marc Zyngier
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