From: Mark Brown <broonie@kernel.org>
To: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
Oliver Upton <oliver.upton@linux.dev>,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Dave Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: arm64: Constrain the host to the maximum shared SVE VL with pKVM
Date: Wed, 11 Sep 2024 14:33:09 +0100 [thread overview]
Message-ID: <c504578e-a00a-4f8b-a7bd-329fac45aa5f@sirena.org.uk> (raw)
In-Reply-To: <CA+EHjTzk6_hWFnrEiJVYZnY41qGORL7NQdV6S+cobDy+UcAR-Q@mail.gmail.com>
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On Wed, Sep 11, 2024 at 01:02:16PM +0100, Fuad Tabba wrote:
> On Tue, 10 Sept 2024 at 21:26, Mark Brown <broonie@kernel.org> wrote:
> The crash is triggered by arch/arm64/kernel/fpsimd.c:487
> (fpsimd_save_user_state(): if (WARN_ON(sve_get_vl() != vl)) ...) ,
> which ends up issuing a SIGKILL.
> The easiest way to consistently reproduce the crash is with a host and
> a guest both running the sve stress test (the one in the arm64
> selftests).
Hrm, I'm not able to reproduce that...
> I think the issue is that this patch doesn't cover all the cases that
> are setting or assuming ZCR_ELx_LEN_MASK as the vector length.
We can't ever assume that VL is ZCR_ELx_LEN_MASK since that might not be
physically supported, and hopefully for a symmetric system the number
read back from RDVL should end up being the same. Though trying to make
the change you suggested *is* triggering something which is fun.
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prev parent reply other threads:[~2024-09-11 13:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-10 20:21 Mark Brown
2024-09-11 11:14 ` Dave Martin
2024-09-11 12:02 ` Fuad Tabba
2024-09-11 13:33 ` Mark Brown [this message]
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