From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: lantianyu1986@gmail.com
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, rkrcmar@redhat.com, corbet@lwn.net,
kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, sashal@kernel.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org,
michael.h.kelley@microsoft.com
Subject: Re: [PATCH V3 0/3] KVM/Hyper-V: Add Hyper-V direct tlb flush support
Date: Tue, 27 Aug 2019 08:41:43 +0200 [thread overview]
Message-ID: <87ftlnm7o8.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20190819131737.26942-1-Tianyu.Lan@microsoft.com>
lantianyu1986@gmail.com writes:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>
> This patchset is to add Hyper-V direct tlb support in KVM. Hyper-V
> in L0 can delegate L1 hypervisor to handle tlb flush request from
> L2 guest when direct tlb flush is enabled in L1.
>
> Patch 2 introduces new cap KVM_CAP_HYPERV_DIRECT_TLBFLUSH to enable
> feature from user space. User space should enable this feature only
> when Hyper-V hypervisor capability is exposed to guest and KVM profile
> is hided. There is a parameter conflict between KVM and Hyper-V hypercall.
> We hope L2 guest doesn't use KVM hypercall when the feature is
> enabled. Detail please see comment of new API
> "KVM_CAP_HYPERV_DIRECT_TLBFLUSH"
I was thinking about this for awhile and I think I have a better
proposal. Instead of adding this new capability let's enable direct TLB
flush when KVM guest enables Hyper-V Hypercall page (writes to
HV_X64_MSR_HYPERCALL) - this guarantees that the guest doesn't need KVM
hypercalls as we can't handle both KVM-style and Hyper-V-style
hypercalls simultaneously and kvm_emulate_hypercall() does:
if (kvm_hv_hypercall_enabled(vcpu->kvm))
return kvm_hv_hypercall(vcpu);
What do you think?
(and instead of adding the capability we can add kvm.ko module parameter
to enable direct tlb flush unconditionally, like
'hv_direct_tlbflush=-1/0/1' with '-1' being the default (autoselect
based on Hyper-V hypercall enablement, '0' - permanently disabled, '1' -
permanenetly enabled)).
--
Vitaly
next prev parent reply other threads:[~2019-08-27 6:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 13:17 [PATCH V3 0/3] KVM/Hyper-V: Add Hyper-V direct tlb flush support lantianyu1986
2019-08-19 13:17 ` [PATCH V3 1/3] x86/Hyper-V: Fix definition of struct hv_vp_assist_page lantianyu1986
2019-08-19 13:30 ` Thomas Gleixner
2019-08-19 13:17 ` [PATCH V3 2/3] KVM/Hyper-V: Add new KVM cap KVM_CAP_HYPERV_DIRECT_TLBFLUSH lantianyu1986
2019-08-19 13:27 ` Thomas Gleixner
2019-08-20 12:38 ` Tianyu Lan
2019-08-19 13:17 ` [PATCH V3 3/3] KVM/Hyper-V/VMX: Add direct tlb flush support lantianyu1986
2019-08-19 13:29 ` Thomas Gleixner
2019-08-27 6:41 ` Vitaly Kuznetsov [this message]
2019-08-27 12:17 ` [PATCH V3 0/3] KVM/Hyper-V: Add Hyper-V " Tianyu Lan
2019-08-27 12:33 ` Tianyu Lan
2019-08-27 12:38 ` Vitaly Kuznetsov
2019-08-27 13:07 ` Tianyu Lan
2019-08-27 13:29 ` Vitaly Kuznetsov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87ftlnm7o8.fsf@vitty.brq.redhat.com \
--to=vkuznets@redhat.com \
--cc=Tianyu.Lan@microsoft.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=haiyangz@microsoft.com \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=kys@microsoft.com \
--cc=lantianyu1986@gmail.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michael.h.kelley@microsoft.com \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=sashal@kernel.org \
--cc=sthemmin@microsoft.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).