linux-kernel - Re: [RFC PATCH 2/2] KVM: TDX: Kick off vCPUs when SEAMCALL is busy during TD page removal

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Message-ID: <Z0VtCHqdxwu4YcY+@yzhao56-desk.sh.intel.com>
Date: Tue, 26 Nov 2024 14:39:04 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, "x86@...nel.org"
	<x86@...nel.org>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "Hunter, Adrian"
	<adrian.hunter@...el.com>, "Lindgren, Tony" <tony.lindgren@...el.com>,
	"dmatlack@...gle.com" <dmatlack@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"Huang, Kai" <kai.huang@...el.com>, "nik.borisov@...e.com"
	<nik.borisov@...e.com>
Subject: Re: [RFC PATCH 2/2] KVM: TDX: Kick off vCPUs when SEAMCALL is busy
 during TD page removal

On Tue, Nov 26, 2024 at 08:47:42AM +0800, Edgecombe, Rick P wrote:
> On Thu, 2024-11-21 at 19:57 +0800, Yan Zhao wrote:
> >  
> > +static void tdx_no_vcpus_enter_start(struct kvm *kvm)
> > +{
> 
> I wonder if an mmu write lock assert here would be excessive.
Hmm, I didn't do it because all current callers already assert on that.

But asserting on that would be safer if the function itself doesn't take a lock
or a counter.


> > +	kvm_make_all_cpus_request(kvm, KVM_REQ_NO_VCPU_ENTER_INPROGRESS);
> > +}
> > +
> > +static void tdx_no_vcpus_enter_stop(struct kvm *kvm)
> > +{
> > +	struct kvm_vcpu *vcpu;
> > +	unsigned long i;
> > +
> > +	kvm_for_each_vcpu(i, vcpu, kvm)
> > +		kvm_clear_request(KVM_REQ_NO_VCPU_ENTER_INPROGRESS, vcpu);
> > +}
> > +
>