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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	kvm@vger.kernel.org, x86@kernel.org,
	"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>, Bandan Das <bsd@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 7/7] x86/kvm: use Enlightened VMCS when running on Hyper-V
Date: Thu, 15 Mar 2018 19:04:35 +0100	[thread overview]
Message-ID: <87sh919pvw.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20180315172852.GA21667@flask> ("Radim \=\?utf-8\?B\?S3LEjW3DocWZ\?\= \=\?utf-8\?B\?Iidz\?\= message of "Thu, 15 Mar 2018 18:28:52 +0100")

Radim Krčmář <rkrcmar@redhat.com> writes:

> 2018-03-15 18:02+0100, Radim Krčmář:
>> We actually already have mov in the assembly:
>> 
>>   "cmp %%" _ASM_SP ", %c[host_rsp](%0) \n\t"
>
> Oh hell, I didn't pay attention to this line before.
>

This is still going to work if we conditionally replace it with pointer
to evmcs as you suggested before but ...


>>   "je 1f \n\t"
>>   "mov %%" _ASM_SP ", %c[host_rsp](%0) \n\t" // here
>>   __ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
>
> I bet this path is executed only once in VM's lifetime and what we're
> doing is wasting more resources than we're ever going to save ...
>

yes, we're not gonna save anything...

-- 
  Vitaly

  reply	other threads:[~2018-03-15 18:04 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-09 14:02 [PATCH v3 0/7] Enlightened VMCS support for KVM on Hyper-V Vitaly Kuznetsov
2018-03-09 14:02 ` [PATCH v3 1/7] x86/hyper-v: move hyperv.h out of uapi Vitaly Kuznetsov
2018-03-13 22:46   ` Michael Kelley (EOSG)
2018-03-14  9:35     ` Vitaly Kuznetsov
2018-03-14 16:13   ` Christoph Hellwig
2018-03-14 16:42     ` Joshua R. Poulson
2018-03-15  7:31       ` Christoph Hellwig
2018-03-09 14:02 ` [PATCH v3 2/7] x86/hyper-v: move definitions from TLFS to hyperv-tlfs.h Vitaly Kuznetsov
2018-03-13 22:51   ` Michael Kelley (EOSG)
2018-03-09 14:02 ` [PATCH v3 3/7] x86/kvm: rename HV_X64_MSR_APIC_ASSIST_PAGE to HV_X64_MSR_VP_ASSIST_PAGE Vitaly Kuznetsov
2018-03-09 14:02 ` [PATCH v3 4/7] x86/hyper-v: allocate and use Virtual Processor Assist Pages Vitaly Kuznetsov
2018-03-13 23:08   ` Michael Kelley (EOSG)
2018-03-14 15:15   ` Thomas Gleixner
2018-03-15 10:10     ` Vitaly Kuznetsov
2018-03-15 11:45       ` Thomas Gleixner
2018-03-15 13:48         ` Peter Zijlstra
2018-03-15 13:57           ` Thomas Gleixner
2018-03-09 14:02 ` [PATCH v3 5/7] x86/hyper-v: define struct hv_enlightened_vmcs and clean field bits Vitaly Kuznetsov
2018-03-13 23:09   ` Michael Kelley (EOSG)
2018-03-09 14:02 ` [PATCH v3 6/7] x86/hyper-v: detect nested features Vitaly Kuznetsov
2018-03-13 23:11   ` Michael Kelley (EOSG)
2018-03-09 14:02 ` [PATCH v3 7/7] x86/kvm: use Enlightened VMCS when running on Hyper-V Vitaly Kuznetsov
2018-03-09 14:08   ` Thomas Gleixner
2018-03-12 14:19     ` Vitaly Kuznetsov
2018-03-13 19:12       ` Radim Krčmář
2018-03-14 17:20         ` Vitaly Kuznetsov
2018-03-14 14:54       ` Paolo Bonzini
2018-03-14 15:19       ` Thomas Gleixner
2018-03-14 17:22         ` Vitaly Kuznetsov
2018-03-14 19:59           ` Thomas Gleixner
2018-03-14 20:06             ` Peter Zijlstra
2018-03-14 14:53   ` Paolo Bonzini
2018-03-15  9:56     ` Vitaly Kuznetsov
2018-03-15 11:01       ` Paolo Bonzini
2018-03-15 15:19     ` Vitaly Kuznetsov
2018-03-15 17:02       ` Radim Krčmář
2018-03-15 17:28         ` Radim Krčmář
2018-03-15 18:04           ` Vitaly Kuznetsov [this message]
2018-03-15 19:28         ` Thomas Gleixner
2018-03-15 19:43           ` Radim Krčmář

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