Received-SPF: pass (google.com: domain of linux-kernel+bounces-82121-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Mon, 26 Feb 2024 10:07:12 -0800
From: Isaku Yamahata <isaku.yamahata@linux.intel.com>
To: David Matlack <dmatlack@google.com>
Cc: Sean Christopherson <seanjc@google.com>, 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>, isaku.yamahata@linux.intel.com
Subject: Re: [PATCH v18 064/121] KVM: TDX: Create initial guest memory
Message-ID: <20240226180712.GF177224@ls.amr.corp.intel.com>
References: <cover.1705965634.git.isaku.yamahata@intel.com>
 <97bb1f2996d8a7b828cd9e3309380d1a86ca681b.1705965635.git.isaku.yamahata@intel.com>
 <Zbrj5WKVgMsUFDtb@google.com>
 <CALzav=diVvCJnJpuKQc7-KeogZw3cTFkzuSWu6PLAHCONJBwhg@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CALzav=diVvCJnJpuKQc7-KeogZw3cTFkzuSWu6PLAHCONJBwhg@mail.gmail.com>

On Thu, Feb 01, 2024 at 03:06:46PM -0800,
David Matlack <dmatlack@google.com> wrote:

> +Vipin Sharma
> 
> On Wed, Jan 31, 2024 at 4:21 PM 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/wishing we
> > can turn this into a generic KVM ioctl() to allow userspace to pre-map guest
> > memory[*].
> >
> > If we're going to carry non-trivial code, we might as well squeeze as much use
> > out of it as we can.
> >
> > Beyond wanting to shove this into KVM_MEMORY_ENCRYPT_OP, is there any reason why
> > this is a VM ioctl() and not a vCPU ioctl()?  Very roughly, couldn't we use a
> > struct like this as input to a vCPU ioctl() that maps memory, and optionally
> > 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 that most
> > of the code in this function is generic.
> >
> > [*] https://lore.kernel.org/all/65262e67-7885-971a-896d-ad9c0a760907@polito.it
> 
> We would also be interested in such an API to reduce the guest
> performance impact of intra-host migration.

I introduce KVM_MEMORY_MAPPING and KVM_CAP_MEMORY_MAPPING with v19.
We can continue the discussion there.
-- 
Isaku Yamahata <isaku.yamahata@linux.intel.com>