From: Roman Kagan <rkagan@virtuozzo.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
"Haiyang Zhang" <haiyangz@microsoft.com>,
"Stephen Hemminger" <sthemmin@microsoft.com>,
"Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
"Mohammed Gamal" <mmorsy@redhat.com>,
"Cathy Avery" <cavery@redhat.com>,
"Wanpeng Li" <wanpeng.li@hotmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/5] KVM: x86: hyperv: introduce vp_index_to_vcpu_idx mapping
Date: Fri, 29 Jun 2018 15:52:16 +0300 [thread overview]
Message-ID: <20180629125216.GC15656@rkaganb.sw.ru> (raw)
In-Reply-To: <87tvplddrr.fsf@vitty.brq.redhat.com>
On Fri, Jun 29, 2018 at 01:37:44PM +0200, Vitaly Kuznetsov wrote:
> The problem we're trying to solve here is: with PV TLB flush and IPI we
> need to walk through the supplied list of VP_INDEXes and get VCPU
> ids. Usually they match. But in case they don't [...]
Why wouldn't they *in practice*? Only if the userspace wanted to be
funny and assigned VP_INDEXes randomly? I'm not sure we need to
optimize for this case.
Note that the userspace can actually do nasty things with these
VP_INDEXes, like, say, have them non-unique. We need to be resilent to
it, but don't need to optimize for it.
I think I'd rather have a warning in kvm_hv_set_msr if the VP_INDEX
being assigned is not equal to the vcpu index, and start worrying about
optimization only if this warning starts being triggered by real
hypervisor applications.
Anyway I don't see an urgent need to bloat this patchset with optimizing
this translation; it can be done separately, if needed.
Roman.
next prev parent reply other threads:[~2018-06-29 12:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-28 13:53 [PATCH v2 0/5] KVM: x86: hyperv: PV IPI support for Windows guests Vitaly Kuznetsov
2018-06-28 13:53 ` [PATCH v2 1/5] KVM: x86: hyperv: optimize 'all cpus' case in kvm_hv_flush_tlb() Vitaly Kuznetsov
2018-06-28 13:53 ` [PATCH v2 2/5] KVM: x86: hyperv: introduce vp_index_to_vcpu_idx mapping Vitaly Kuznetsov
2018-06-28 18:49 ` kbuild test robot
2018-06-28 19:09 ` [PATCH] KVM: x86: hyperv: fix semicolon.cocci warnings kbuild test robot
2018-06-28 19:09 ` [PATCH v2 2/5] KVM: x86: hyperv: introduce vp_index_to_vcpu_idx mapping kbuild test robot
2018-06-29 10:11 ` Roman Kagan
2018-06-29 10:26 ` Vitaly Kuznetsov
2018-06-29 11:12 ` Roman Kagan
2018-06-29 11:37 ` Vitaly Kuznetsov
2018-06-29 12:52 ` Roman Kagan [this message]
2018-06-29 13:10 ` Vitaly Kuznetsov
2018-06-29 14:32 ` Roman Kagan
2018-06-29 15:25 ` Vitaly Kuznetsov
2018-06-29 15:55 ` Roman Kagan
2018-06-28 13:53 ` [PATCH v2 3/5] KVM: x86: hyperv: use vp_idx_to_vcpu_idx() in kvm_hv_flush_tlb() Vitaly Kuznetsov
2018-06-28 13:53 ` [PATCH v2 4/5] x86/hyper-v: rename ipi_arg_{ex,non_ex} structures Vitaly Kuznetsov
2018-06-28 13:53 ` [PATCH v2 5/5] KVM: x86: hyperv: implement PV IPI send hypercalls Vitaly Kuznetsov
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