linux-kernel - Re: [PATCH v4 0/4] Add support for XMM fast hypercalls

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Date:   Tue, 6 Jul 2021 17:15:36 +0200
From:   Siddharth Chandrasekaran <sidcha@...zon.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Siddharth Chandrasekaran <sidcha.dev@...il.com>,
        Alexander Graf <graf@...zon.com>,
        Evgeny Iakovlev <eyakovl@...zon.de>,
        Liran Alon <liran@...zon.com>,
        Ioannis Aslanidis <iaslan@...zon.de>,
        <linux-hyperv@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>
Subject: Re: [PATCH v4 0/4] Add support for XMM fast hypercalls

On Tue, Jul 06, 2021 at 05:04:59PM +0200, Paolo Bonzini wrote:
> On 30/06/21 13:56, Siddharth Chandrasekaran wrote:
> > On Wed, May 26, 2021 at 10:56:07AM +0200, Siddharth Chandrasekaran wrote:
> > > Hyper-V supports the use of XMM registers to perform fast hypercalls.
> > > This allows guests to take advantage of the improved performance of the
> > > fast hypercall interface even though a hypercall may require more than
> > > (the current maximum of) two general purpose registers.
> > > 
> > > The XMM fast hypercall interface uses an additional six XMM registers
> > > (XMM0 to XMM5) to allow the caller to pass an input parameter block of
> > > up to 112 bytes. Hyper-V can also return data back to the guest in the
> > > remaining XMM registers that are not used by the current hypercall.
> > > 
> > > Although the Hyper-v TLFS mentions that a guest cannot use this feature
> > > unless the hypervisor advertises support for it, some hypercalls which
> > > we plan on upstreaming in future uses them anyway. This patchset adds
> > > necessary infrastructure for handling input/output via XMM registers and
> > > patches kvm_hv_flush_tlb() to use xmm input arguments.
> > 
> > Hi Paolo,
> > 
> > Are you expecting more reviews on these patches?
> 
> They are part of 5.14 already. :)

Ahh, I see them now. I was expecting them to show up in master - that was
the confusion.

Thanks! :)

~ Sid



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