Re: [PATCH v2 3/7] KVM: x86: hyper-v: Move the remote TLB flush logic out of vmx

From: Vineeth Pillai <viremana@linux.microsoft.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
	Lan Tianyu <Tianyu.Lan@microsoft.com>,
	Michael Kelley <mikelley@microsoft.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Wei Liu <wei.liu@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	viremana@linux.microsoft.com
Subject: Re: [PATCH v2 3/7] KVM: x86: hyper-v: Move the remote TLB flush logic out of vmx
Date: Fri, 16 Apr 2021 12:39:00 -0400	[thread overview]
Message-ID: <a01a13e4-4c11-962b-83ad-e7fc64cc3be8@linux.microsoft.com> (raw)
In-Reply-To: <87y2di7hiz.fsf@vitty.brq.redhat.com>


On 4/16/2021 4:36 AM, Vitaly Kuznetsov wrote:
>
>>   struct kvm_vm_stat {
>> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>> index 58fa8c029867..614b4448a028 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
> I still think that using arch/x86/kvm/hyperv.[ch] for KVM-on-Hyper-V is
> misleading. Currently, these are dedicated to emulating Hyper-V
> interface to KVM guests and this is orthogonal to nesting KVM on
> Hyper-V. As a solution, I'd suggest you either:
> - Put the stuff in x86.c
> - Create a dedicated set of files, e.g. 'kvmonhyperv.[ch]' (I also
> thought about 'hyperv_host.[ch]' but then I realized it's equally
> misleading as one can read this as 'KVM is acting as Hyper-V host').
>
> Personally, I'd vote for the later. Besides eliminating confusion, the
> benefit of having dedicated files is that we can avoid compiling them
> completely when !IS_ENABLED(CONFIG_HYPERV) (#ifdefs in C are ugly).
Makes sense, creating new set of files looks good to me. The default 
hyperv.c
for hyperv emulation also seems misleading - probably we should rename it
to hyperv_host_emul.[ch] or similar. That way, probably I can use 
hyperv.[ch]
for kvm on hyperv code. If you feel, thats too big of a churn, I shall use
kvm_on_hyperv.[ch] (to avoid reading the file differently). What do you 
think?


>> @@ -10470,7 +10474,6 @@ void kvm_arch_free_vm(struct kvm *kvm)
>>   	vfree(kvm);
>>   }
>>   
>> -
> Stray change?
It was kinda leftover, but I thought I'd keep it as it removes and 
unnecessary line.

Thanks,
Vineeth