linux-kernel - Re: [PATCH v3 1/3] arm: perf: Include threshold control fields valid in PMEVTYPER mask

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZSZb2H8O5fuU3UrA@linux.dev>
Date:   Wed, 11 Oct 2023 08:24:56 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     James Clark <james.clark@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, suzuki.poulose@....com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Russell King <linux@...linux.org.uk>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Zaid Al-Bassam <zalbassam@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.linux.dev
Subject: Re: [PATCH v3 1/3] arm: perf: Include threshold control fields valid
 in PMEVTYPER mask

Hi James,

On Tue, Oct 10, 2023 at 03:15:41PM +0100, James Clark wrote:
> FEAT_PMUv3_TH (Armv8.8) adds two new fields to PMEVTYPER, so include
> them in the mask. These aren't writable on 32 bit kernels as they are in
> the high part of the register, so split the mask definition to the asm
> files for each platform.
> 
> Now where the value is used in some parts of KVM, include the asm file.
> There is no impact on guest PMUs emulated with KVM because the new
> fields are ignored when constructing the attributes for opening the
> event. But if threshold support is added to KVM at a later time no
> change to the mask will be needed.

KVM should treat TH and TC as RES0 if the feature isn't virtualized. I'd
rather move KVM away from using ARMV8_PMU_EVTYPE_MASK in the first
place. Looks like we already have an issue with the NSH bit, so I've
sent the below patch to fix it.

https://lore.kernel.org/kvmarm/20231011081649.3226792-3-oliver.upton@linux.dev/

-- 
Thanks,
Oliver