linux-kernel - Re: [PATCH v19 070/130] KVM: TDX: TDP MMU TDX support

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Date: Fri, 31 May 2024 22:16:58 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Chen, Yu C" <yu.c.chen@...el.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>
CC: "Gao, Chao" <chao.gao@...el.com>, "Zhang, Tina" <tina.zhang@...el.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>,
	"Yin, Fengwei" <fengwei.yin@...el.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "Chen, Bo2" <chen.bo@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Aktas, Erdem"
	<erdemaktas@...gle.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Yuan, Hang"
	<hang.yuan@...el.com>, "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"isaku.yamahata@...ux.intel.com" <isaku.yamahata@...ux.intel.com>
Subject: Re: [PATCH v19 070/130] KVM: TDX: TDP MMU TDX support

On Wed, 2024-05-29 at 15:56 +0800, Chen Yu wrote:
> > > You don't like IS_ENABLED(CONFIG_HYPERV) || IS_ENABLED(CONFIG_TDX_HOST) in
> > > many
> > > places?  Then, we can do something like the followings.  Although It would
> > > be
> > > a bit ugly than the commit of 0277022a77a5, it's better to keep the
> > > intention
> > > of it.
> > > 
> > 
> > Ah, we have already __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE. We can use it.
> 
> Yes, and there is also __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS so we can use
> ifdef __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE when needed.

In the current dev branch we already have:
#if IS_ENABLED(CONFIG_HYPERV) || IS_ENABLED(CONFIG_INTEL_TDX_HOST)
	int  (*flush_remote_tlbs)(struct kvm *kvm);
#endif

It was apparently reported by Vijay Dhanraj also.


0277022a77a5 has:
    Declare the kvm_x86_ops hooks used to wire up paravirt TLB flushes when
    running under Hyper-V if and only if CONFIG_HYPERV!=n.  Wrapping yet more
    code with IS_ENABLED(CONFIG_HYPERV) eliminates a handful of conditional
    branches, and makes it super obvious why the hooks *might* be valid.
    
So the bug should already be fixed, but if anyone has a strong style opinion
please send a fixup. None of the options jump out to me as obviously better.