Received-SPF: pass (google.com: domain of linux-kernel+bounces-48977-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Precedence: bulk
MIME-Version: 1.0
References: <cover.1705965634.git.isaku.yamahata@intel.com>
 <97bb1f2996d8a7b828cd9e3309380d1a86ca681b.1705965635.git.isaku.yamahata@intel.com>
 <Zbrj5WKVgMsUFDtb@google.com>
In-Reply-To: <Zbrj5WKVgMsUFDtb@google.com>
From: David Matlack <dmatlack@google.com>
Date: Thu, 1 Feb 2024 15:06:46 -0800
Message-ID: <CALzav=diVvCJnJpuKQc7-KeogZw3cTFkzuSWu6PLAHCONJBwhg@mail.gmail.com>
Subject: Re: [PATCH v18 064/121] KVM: TDX: Create initial guest memory
To: Sean Christopherson <seanjc@google.com>
Cc: isaku.yamahata@intel.com, kvm@vger.kernel.org, 
	linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, 
	Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com, Sagi Shahar <sagis@google.com>, 
	Kai Huang <kai.huang@intel.com>, chen.bo@intel.com, hang.yuan@intel.com, 
	tina.zhang@intel.com, gkirkpatrick@google.com, 
	Vipin Sharma <vipinsh@google.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

+Vipin Sharma

On Wed, Jan 31, 2024 at 4:21=E2=80=AFPM Sean Christopherson <seanjc@google.=
com> wrote:
> On Mon, Jan 22, 2024, isaku.yamahata@intel.com wrote:
>
> The real reason for this drive-by pseudo-review is that I am hoping/wishi=
ng we
> can turn this into a generic KVM ioctl() to allow userspace to pre-map gu=
est
> memory[*].
>
> If we're going to carry non-trivial code, we might as well squeeze as muc=
h use
> out of it as we can.
>
> Beyond wanting to shove this into KVM_MEMORY_ENCRYPT_OP, is there any rea=
son why
> this is a VM ioctl() and not a vCPU ioctl()?  Very roughly, couldn't we u=
se a
> struct like this as input to a vCPU ioctl() that maps memory, and optiona=
lly
> initializes memory from @source?
>
>         struct kvm_memory_mapping {
>                 __u64 base_gfn;
>                 __u64 nr_pages;
>                 __u64 flags;
>                 __u64 source;
>         }
>
> TDX would need to do special things for copying the source, but beyond th=
at most
> of the code in this function is generic.
>
> [*] https://lore.kernel.org/all/65262e67-7885-971a-896d-ad9c0a760907@poli=
to.it

We would also be interested in such an API to reduce the guest
performance impact of intra-host migration.