From: Marc Zyngier <maz@kernel.org>
To: Zenghui Yu <yuzenghui@huawei.com>
Cc: <kvmarm@lists.linux.dev>, <linux-arm-kernel@lists.infradead.org>,
<kvm@vger.kernel.org>, James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Joey Gouly <joey.gouly@arm.com>,
Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
Xu Zhao <zhaoxu.35@bytedance.com>,
Eric Auger <eric.auger@redhat.com>
Subject: Re: [PATCH v2 06/11] KVM: arm64: Use vcpu_idx for invalidation tracking
Date: Thu, 21 Sep 2023 13:58:49 +0100 [thread overview]
Message-ID: <86zg1fof7a.wl-maz@kernel.org> (raw)
In-Reply-To: <ce3a9022-0d4e-ad8d-8a32-a9759f718ab3@huawei.com>
On Thu, 21 Sep 2023 10:16:42 +0100,
Zenghui Yu <yuzenghui@huawei.com> wrote:
>
> On 2023/9/21 2:17, Marc Zyngier wrote:
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> > arch/arm64/kvm/arm.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> > index 872679a0cbd7..23c22dbd1969 100644
> > --- a/arch/arm64/kvm/arm.c
> > +++ b/arch/arm64/kvm/arm.c
> > @@ -438,9 +438,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> > * We might get preempted before the vCPU actually runs, but
> > * over-invalidation doesn't affect correctness.
> > */
> > - if (*last_ran != vcpu->vcpu_id) {
> > + if (*last_ran != vcpu->vcpu_idx) {
> > kvm_call_hyp(__kvm_flush_cpu_context, mmu);
> > - *last_ran = vcpu->vcpu_id;
> > + *last_ran = vcpu->vcpu_idx;
> > }
> > vcpu->cpu = cpu;
>
> Isn't the original code (using vcpu_id) enough to detect a different
> previously run VCPU? What am I missing?
It is in theory enough. However, I couldn't convince myself of the
*unicity* of the vcpu_id field. It really feels like something as
crucial as the TLB invalidation shouldn't rely on something that is
controlled by userspace.
And I really should write a commit message to capture this.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2023-09-21 12:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-20 18:17 [PATCH v2 00/11] KVM: arm64: Accelerate lookup of vcpus by MPIDR values (and other fixes) Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 01/11] KVM: arm64: vgic: Make kvm_vgic_inject_irq() take a vcpu pointer Marc Zyngier
2023-09-21 9:11 ` Zenghui Yu
2023-09-21 11:20 ` Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 02/11] KVM: arm64: vgic-its: Treat the collection target address as a vcpu_id Marc Zyngier
2023-09-21 9:14 ` Zenghui Yu
2023-09-21 11:46 ` Marc Zyngier
2023-09-21 13:12 ` Zenghui Yu
2023-09-20 18:17 ` [PATCH v2 03/11] KVM: arm64: vgic-v3: Refactor GICv3 SGI generation Marc Zyngier
2023-09-21 9:42 ` Joey Gouly
2023-09-21 11:13 ` Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 04/11] KVM: arm64: vgic-v2: Use cpuid from userspace as vcpu_id Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 05/11] KVM: arm64: vgic: Use vcpu_idx for the debug information Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 06/11] KVM: arm64: Use vcpu_idx for invalidation tracking Marc Zyngier
2023-09-21 9:16 ` Zenghui Yu
2023-09-21 12:58 ` Marc Zyngier [this message]
2023-09-20 18:17 ` [PATCH v2 07/11] KVM: arm64: Simplify kvm_vcpu_get_mpidr_aff() Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 08/11] KVM: arm64: Build MPIDR to vcpu index cache at runtime Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 09/11] KVM: arm64: Fast-track kvm_mpidr_to_vcpu() when mpidr_data is available Marc Zyngier
2023-09-20 18:17 ` [PATCH v2 10/11] KVM: arm64: vgic-v3: Optimize affinity-based SGI injection Marc Zyngier
2023-09-21 9:32 ` Zenghui Yu
2023-09-20 18:17 ` [PATCH v2 11/11] KVM: arm64: Clarify the ordering requirements for vcpu/RD creation Marc Zyngier
2023-09-21 2:11 ` [PATCH v2 00/11] KVM: arm64: Accelerate lookup of vcpus by MPIDR values (and other fixes) Oliver Upton
2023-09-21 9:39 ` Zenghui Yu
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