linux-kernel - Re: [PATCH 1/7] KVM: TDX: Return -EBUSY when tdh_mem_page_add() encounters TDX_OPERAND

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Message-ID: <Z4dAru7SlXKfckZx@yzhao56-desk.sh.intel.com>
Date: Wed, 15 Jan 2025 12:59:26 +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>, "Huang, Kai"
	<kai.huang@...el.com>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Lindgren,
 Tony" <tony.lindgren@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Chatre, Reinette"
	<reinette.chatre@...el.com>, "dmatlack@...gle.com" <dmatlack@...gle.com>,
	"Hunter, Adrian" <adrian.hunter@...el.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>
Subject: Re: [PATCH 1/7] KVM: TDX: Return -EBUSY when tdh_mem_page_add()
 encounters TDX_OPERAND_BUSY

On Wed, Jan 15, 2025 at 06:24:34AM +0800, Edgecombe, Rick P wrote:
> On Mon, 2025-01-13 at 10:10 +0800, Yan Zhao wrote:
> > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > index d0dc3200fa37..1cf3ef0faff7 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -3024,13 +3024,11 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
> >  	}
> >  
> >  	ret = 0;
> > -	do {
> > -		err = tdh_mem_page_add(kvm_tdx->tdr_pa, gpa, pfn_to_hpa(pfn),
> > -				       pfn_to_hpa(page_to_pfn(page)),
> > -				       &entry, &level_state);
> > -	} while (err == TDX_ERROR_SEPT_BUSY);
> > +	err = tdh_mem_page_add(kvm_tdx->tdr_pa, gpa, pfn_to_hpa(pfn),
> > +			       pfn_to_hpa(page_to_pfn(page)),
> > +			       &entry, &level_state);
> >  	if (err) {
> > -		ret = -EIO;
> > +		ret = unlikely(err & TDX_OPERAND_BUSY) ? -EBUSY : -EIO;
> >  		goto out;
> >  	}
> 
> Should we just squash this into "KVM: TDX: Add an ioctl to create initial guest
> memory"? I guess we get a little more specific log history on this corner as a
> separate patch, but seems strange to add and remove a loop before it even can
> get exercised.
No problem to me.