linux-kernel - Re: [RFC PATCH 5/8] KVM: x86/mmu: Introduce kvm_mmu_map

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Message-ID: <20240319155349.GE1645738@ls.amr.corp.intel.com>
Date: Tue, 19 Mar 2024 08:53:49 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: David Matlack <dmatlack@...gle.com>
Cc: isaku.yamahata@...el.com, kvm@...r.kernel.org, isaku.yamahata@...il.com,
	linux-kernel@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Michael Roth <michael.roth@....com>,
	Federico Parola <federico.parola@...ito.it>,
	isaku.yamahata@...ux.intel.com
Subject: Re: [RFC PATCH 5/8] KVM: x86/mmu: Introduce kvm_mmu_map_page() for
 prepopulating guest memory

On Wed, Mar 06, 2024 at 04:38:53PM -0800,
David Matlack <dmatlack@...gle.com> wrote:

> On 2024-03-01 09:28 AM, isaku.yamahata@...el.com wrote:
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index e4cc7f764980..7d5e80d17977 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -4659,6 +4659,36 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> >  	return direct_page_fault(vcpu, fault);
> >  }
> >  
> > +int kvm_mmu_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> > +		     u8 max_level, u8 *goal_level)
> > +{
> > +	struct kvm_page_fault fault = KVM_PAGE_FAULT_INIT(vcpu, gpa, error_code,
> > +							  false, max_level);
> > +	int r;
> > +
> > +	r = __kvm_mmu_do_page_fault(vcpu, &fault);
> 
> If TDP is disabled __kvm_mmu_do_page_fault() will interpret @gpa as a
> GVA no? And if the vCPU is in guest-mode __kvm_mmu_do_page_fault() will
> interpret gpa as a nGPA right?

Just to close the discussion.
As we discussed at [1], I'd lie to restrict the API to TDP MMU only
(with the next version).  If vCPU is in guest-mode or legacy MMU mode, it will
get error.

[1] https://lore.kernel.org/kvm/ZekQFdPlU7RDVt-B@google.com/
-- 
Isaku Yamahata <isaku.yamahata@...el.com>