linux-kernel - Re: [PATCH v13 098/113] KVM: TDX: Handle TDX PV map

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Message-ID: <20230419133841.00001ee8.zhi.wang.linux@gmail.com>
Date:   Wed, 19 Apr 2023 13:38:41 +0300
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Vishal Annapurve <vannapurve@...gle.com>
Cc:     isaku.yamahata@...el.com, dmatlack@...gle.com,
        erdemaktas@...gle.com, isaku.yamahata@...il.com,
        kai.huang@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, pbonzini@...hat.com,
        sagis@...gle.com, seanjc@...gle.com
Subject: Re: [PATCH v13 098/113] KVM: TDX: Handle TDX PV map_gpa hypercall

On Tue, 18 Apr 2023 19:09:04 +0000
Vishal Annapurve <vannapurve@...gle.com> wrote:

> > +static int tdx_map_gpa(struct kvm_vcpu *vcpu)
> > +{
> > +	struct kvm *kvm = vcpu->kvm;
> > +	gpa_t gpa = tdvmcall_a0_read(vcpu);
> > +	gpa_t size = tdvmcall_a1_read(vcpu);
> > +	gpa_t end = gpa + size;
> > +
> > +	if (!IS_ALIGNED(gpa, PAGE_SIZE) || !IS_ALIGNED(size, PAGE_SIZE) ||
> > +	    end < gpa ||
> > +	    end > kvm_gfn_shared_mask(kvm) << (PAGE_SHIFT + 1) ||
> > +	    kvm_is_private_gpa(kvm, gpa) != kvm_is_private_gpa(kvm, end)) {
> > +		tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_INVALID_OPERAND);
> > +		return 1;
> > +	}
> > +
> > +	return tdx_vp_vmcall_to_user(vcpu);
> 
> This will result into exits to userspace for MMIO regions as well. Does it make
> sense to only exit to userspace for guest physical memory regions backed by
> memslots?
> 
I think this is necessary as when passing a PCI device to a TD, the guest needs to convert a MMIO region from private to shared, which is not backed by memslots.
> > +}
> > +