From: Christopher Lameter <cl@linux.com>
To: David Brazdil <dbrazdil@google.com>
Cc: kvmarm@lists.cs.columbia.edu,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH v4 00/10] Independent per-CPU data section for nVHE
Date: Thu, 24 Sep 2020 10:10:52 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.22.394.2009241003100.1613@www.lameter.com> (raw)
In-Reply-To: <20200922204910.7265-1-dbrazdil@google.com>
On Tue, 22 Sep 2020, David Brazdil wrote:
> Introduce '.hyp.data..percpu' as part of ongoing effort to make nVHE
> hyp code self-contained and independent of the rest of the kernel.
The percpu subsystems point is to enable the use of special hardware
instructions that can perform address calculation and a memory operation
in one interruptible instruction. This is in particular useful to avoid
higher overhead for memory management related counters because preempt
disable/enable etc can be avoided.
ARM cannot do that and thus has a LC/SC loop.
This is a patchset for ARM64 so its not clear to me what kind of advantage
there would be against a simple implementation that does a regular fetch
from a base address with an offset.
> Main benefits:
> * independent nVHE per-CPU data section that can be unmapped from host,
> * more robust linking of nVHE hyp code,
> * no need for hyp-specific macros to access per-CPU variables.
Maybe simply don't use percpu variables for your arm code? Those pointers
to data will be much more indepedent of the rest of the kernel and allow a
much higher degree of being self-contained.
next prev parent reply other threads:[~2020-09-24 10:10 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 20:49 David Brazdil
2020-09-22 20:49 ` [PATCH v4 01/10] kvm: arm64: Partially link nVHE hyp code, simplify HYPCOPY David Brazdil
2020-09-22 20:49 ` [PATCH v4 02/10] kvm: arm64: Move nVHE hyp namespace macros to hyp_image.h David Brazdil
2020-09-22 20:49 ` [PATCH v4 03/10] kvm: arm64: Only define __kvm_ex_table for CONFIG_KVM David Brazdil
2020-09-22 20:49 ` [PATCH v4 04/10] kvm: arm64: Remove __hyp_this_cpu_read David Brazdil
2020-09-29 17:30 ` Will Deacon
2020-09-22 20:49 ` [PATCH v4 05/10] kvm: arm64: Remove hyp_adr/ldr_this_cpu David Brazdil
2020-09-29 17:34 ` Will Deacon
2020-09-29 17:46 ` Marc Zyngier
2020-09-22 20:49 ` [PATCH v4 06/10] kvm: arm64: Add helpers for accessing nVHE hyp per-cpu vars David Brazdil
2020-09-22 20:49 ` [PATCH v4 07/10] kvm: arm64: Duplicate arm64_ssbd_callback_required for nVHE hyp David Brazdil
2020-09-29 17:37 ` Will Deacon
2020-09-22 20:49 ` [PATCH v4 08/10] kvm: arm64: Create separate instances of kvm_host_data for VHE/nVHE David Brazdil
2020-09-22 20:49 ` [PATCH v4 09/10] kvm: arm64: Set up hyp percpu data for nVHE David Brazdil
2020-09-29 17:50 ` Will Deacon
2020-09-22 20:49 ` [PATCH v4 10/10] kvm: arm64: Remove unnecessary hyp mappings David Brazdil
2020-09-29 17:49 ` Will Deacon
2020-09-24 10:10 ` Christopher Lameter [this message]
2020-10-02 8:19 ` [PATCH v4 00/10] Independent per-CPU data section for nVHE Marc Zyngier
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