From: Mark Brown <broonie@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: kernel-team@android.com, kvm@vger.kernel.org,
Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/5] KVM: arm64: Get rid of host SVE tracking/saving
Date: Tue, 23 Nov 2021 12:33:20 +0000 [thread overview]
Message-ID: <YZzfkO+HawhyZSjt@sirena.org.uk> (raw)
In-Reply-To: <87mtlvchbe.wl-maz@kernel.org>
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On Tue, Nov 23, 2021 at 10:11:33AM +0000, Marc Zyngier wrote:
> Mark Brown <broonie@kernel.org> wrote:
> > We don't need to change the ABI, the ABI just says we zero the registers
> > that aren't shared with FPSIMD. Instead of doing that on taking a SVE
> > access trap to reenable SVE after having disabled TIF_SVE we could do
> That's not the point I'm trying to make.
> Userspace expects to have lost SVE information over a syscall (even if
> the VL is 128, it expects to have lost P0..P15 and FFR). How do you
> plan to tell userspace that this behaviour has changed?
My point is that this doesn't need to change. Userspace can't tell if
we zeroed the non-shared state on syscall or on some later access trap.
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next prev parent reply other threads:[~2021-11-23 12:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 11:16 [PATCH v2 0/5] KVM: arm64: Rework FPSIMD/SVE tracking Marc Zyngier
2021-10-28 11:16 ` [PATCH v2 1/5] KVM: arm64: Reorder vcpu flag definitions Marc Zyngier
2021-10-28 11:16 ` [PATCH v2 2/5] KVM: arm64: Get rid of host SVE tracking/saving Marc Zyngier
2021-10-28 13:02 ` Mark Brown
2021-11-10 13:19 ` Zenghui Yu
2021-11-22 15:57 ` Marc Zyngier
2021-11-22 17:58 ` Mark Brown
2021-11-22 18:10 ` Marc Zyngier
2021-11-22 18:30 ` Mark Brown
2021-11-23 10:11 ` Marc Zyngier
2021-11-23 12:33 ` Mark Brown [this message]
2021-10-28 11:16 ` [PATCH v2 3/5] KVM: arm64: Introduce flag shadowing TIF_FOREIGN_FPSTATE Marc Zyngier
2021-10-28 11:16 ` [PATCH v2 4/5] KVM: arm64: Stop mapping current thread_info at EL2 Marc Zyngier
2021-10-28 11:16 ` [PATCH v2 5/5] arm64/fpsimd: Document the use of TIF_FOREIGN_FPSTATE by KVM Marc Zyngier
2021-10-28 13:14 ` Mark Brown
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