From: Dan Williams <dan.j.williams@intel.com>
To: Kai Huang <kai.huang@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Brown, Len" <len.brown@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
Rafael J Wysocki <rafael.j.wysocki@intel.com>,
Reinette Chatre <reinette.chatre@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <ak@linux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Isaku Yamahata <isaku.yamahata@intel.com>
Subject: Re: [PATCH v3 00/21] TDX host kernel support
Date: Thu, 28 Apr 2022 20:04:19 -0700 [thread overview]
Message-ID: <CAPcyv4gEwjnNE9cWb_KLZ6C7-UxKdUMZKFPF+LAJ4L1SjByisw@mail.gmail.com> (raw)
In-Reply-To: <fc1ca04d94ad45e79c0297719d5ef50a7c33c352.camel@intel.com>
On Thu, Apr 28, 2022 at 6:40 PM Kai Huang <kai.huang@intel.com> wrote:
>
> On Thu, 2022-04-28 at 12:58 +1200, Kai Huang wrote:
> > On Wed, 2022-04-27 at 17:50 -0700, Dave Hansen wrote:
> > > On 4/27/22 17:37, Kai Huang wrote:
> > > > On Wed, 2022-04-27 at 14:59 -0700, Dave Hansen wrote:
> > > > > In 5 years, if someone takes this code and runs it on Intel hardware
> > > > > with memory hotplug, CPU hotplug, NVDIMMs *AND* TDX support, what happens?
> > > >
> > > > I thought we could document this in the documentation saying that this code can
> > > > only work on TDX machines that don't have above capabilities (SPR for now). We
> > > > can change the code and the documentation when we add the support of those
> > > > features in the future, and update the documentation.
> > > >
> > > > If 5 years later someone takes this code, he/she should take a look at the
> > > > documentation and figure out that he/she should choose a newer kernel if the
> > > > machine support those features.
> > > >
> > > > I'll think about design solutions if above doesn't look good for you.
> > >
> > > No, it doesn't look good to me.
> > >
> > > You can't just say:
> > >
> > > /*
> > > * This code will eat puppies if used on systems with hotplug.
> > > */
> > >
> > > and merrily await the puppy bloodbath.
> > >
> > > If it's not compatible, then you have to *MAKE* it not compatible in a
> > > safe, controlled way.
> > >
> > > > > You can't just ignore the problems because they're not present on one
> > > > > version of the hardware.
> > >
> > > Please, please read this again ^^
> >
> > OK. I'll think about solutions and come back later.
> > >
>
> Hi Dave,
>
> I think we have two approaches to handle memory hotplug interaction with the TDX
> module initialization.
>
> The first approach is simple. We just block memory from being added as system
> RAM managed by page allocator when the platform supports TDX [1]. It seems we
> can add some arch-specific-check to __add_memory_resource() and reject the new
> memory resource if platform supports TDX. __add_memory_resource() is called by
> both __add_memory() and add_memory_driver_managed() so it prevents from adding
> NVDIMM as system RAM and normal ACPI memory hotplug [2].
What if the memory being added *is* TDX capable? What if someone
wanted to manage a memory range as soft-reserved and move it back and
forth from the core-mm to device access. That should be perfectly
acceptable as long as the memory is TDX capable.
> The second approach is relatively more complicated. Instead of directly
> rejecting the new memory resource in __add_memory_resource(), we check whether
> the memory resource can be added based on CMR and the TDX module initialization
> status. This is feasible as with the latest public P-SEAMLDR spec, we can get
> CMR from P-SEAMLDR SEAMCALL[3]. So we can detect P-SEAMLDR and get CMR info
> during kernel boots. And in __add_memory_resource() we do below check:
>
> tdx_init_disable(); /*similar to cpu_hotplug_disable() */
> if (tdx_module_initialized())
> // reject memory hotplug
> else if (new_memory_resource NOT in CMRs)
> // reject memory hotplug
> else
> allow memory hotplug
> tdx_init_enable(); /*similar to cpu_hotplug_enable() */
>
> tdx_init_disable() temporarily disables TDX module initialization by trying to
> grab the mutex. If the TDX module initialization is already on going, then it
> waits until it completes.
>
> This should work better for future platforms, but would requires non-trivial
> more code as we need to add VMXON/VMXOFF support to the core-kernel to detect
> CMR using SEAMCALL. A side advantage is with VMXON in core-kernel we can
> shutdown the TDX module in kexec().
>
> But for this series I think the second approach is overkill and we can choose to
> use the first simple approach?
This still sounds like it is trying to solve symptoms and not the root
problem. Why must the core-mm never have non-TDX memory when VMs are
fine to operate with either core-mm pages or memory from other sources
like hugetlbfs and device-dax?
next prev parent reply other threads:[~2022-04-29 3:04 UTC|newest]
Thread overview: 156+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-06 4:49 [PATCH v3 00/21] TDX host kernel support Kai Huang
2022-04-06 4:49 ` [PATCH v3 01/21] x86/virt/tdx: Detect SEAM Kai Huang
2022-04-18 22:29 ` Sathyanarayanan Kuppuswamy
2022-04-18 22:50 ` Sean Christopherson
2022-04-19 3:38 ` Kai Huang
2022-04-26 20:21 ` Dave Hansen
2022-04-26 23:12 ` Kai Huang
2022-04-26 23:28 ` Dave Hansen
2022-04-26 23:49 ` Kai Huang
2022-04-27 0:22 ` Sean Christopherson
2022-04-27 0:44 ` Kai Huang
2022-04-27 14:22 ` Dave Hansen
2022-04-27 22:39 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 02/21] x86/virt/tdx: Detect TDX private KeyIDs Kai Huang
2022-04-19 5:39 ` Sathyanarayanan Kuppuswamy
2022-04-19 9:41 ` Kai Huang
2022-04-19 5:42 ` Sathyanarayanan Kuppuswamy
2022-04-19 10:07 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 03/21] x86/virt/tdx: Implement the SEAMCALL base function Kai Huang
2022-04-19 14:07 ` Sathyanarayanan Kuppuswamy
2022-04-20 4:16 ` Kai Huang
2022-04-20 7:29 ` Sathyanarayanan Kuppuswamy
2022-04-20 10:39 ` Kai Huang
2022-04-26 20:37 ` Dave Hansen
2022-04-26 23:29 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 04/21] x86/virt/tdx: Add skeleton for detecting and initializing TDX on demand Kai Huang
2022-04-19 14:53 ` Sathyanarayanan Kuppuswamy
2022-04-20 4:37 ` Kai Huang
2022-04-20 5:21 ` Dave Hansen
2022-04-20 14:30 ` Sathyanarayanan Kuppuswamy
2022-04-20 22:35 ` Kai Huang
2022-04-26 20:53 ` Dave Hansen
2022-04-27 0:43 ` Kai Huang
2022-04-27 14:49 ` Dave Hansen
2022-04-28 0:00 ` Kai Huang
2022-04-28 14:27 ` Dave Hansen
2022-04-28 23:44 ` Kai Huang
2022-04-28 23:53 ` Dave Hansen
2022-04-29 0:11 ` Kai Huang
2022-04-29 0:26 ` Dave Hansen
2022-04-29 0:59 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 05/21] x86/virt/tdx: Detect P-SEAMLDR and TDX module Kai Huang
2022-04-26 20:56 ` Dave Hansen
2022-04-27 0:01 ` Kai Huang
2022-04-27 14:24 ` Dave Hansen
2022-04-27 21:30 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 06/21] x86/virt/tdx: Shut down TDX module in case of error Kai Huang
2022-04-23 15:39 ` Sathyanarayanan Kuppuswamy
2022-04-25 23:41 ` Kai Huang
2022-04-26 1:48 ` Sathyanarayanan Kuppuswamy
2022-04-26 2:12 ` Kai Huang
2022-04-26 20:59 ` Dave Hansen
2022-04-27 0:06 ` Kai Huang
2022-05-18 16:19 ` Sagi Shahar
2022-05-18 23:51 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 07/21] x86/virt/tdx: Do TDX module global initialization Kai Huang
2022-04-20 22:27 ` Sathyanarayanan Kuppuswamy
2022-04-20 22:37 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 08/21] x86/virt/tdx: Do logical-cpu scope TDX module initialization Kai Huang
2022-04-24 1:27 ` Sathyanarayanan Kuppuswamy
2022-04-25 23:55 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 09/21] x86/virt/tdx: Get information about TDX module and convertible memory Kai Huang
2022-04-25 2:58 ` Sathyanarayanan Kuppuswamy
2022-04-26 0:05 ` Kai Huang
2022-04-27 22:15 ` Dave Hansen
2022-04-28 0:15 ` Kai Huang
2022-04-28 14:06 ` Dave Hansen
2022-04-28 23:14 ` Kai Huang
2022-04-29 17:47 ` Dave Hansen
2022-05-02 5:04 ` Kai Huang
2022-05-25 4:47 ` Kai Huang
2022-05-25 4:57 ` Kai Huang
2022-05-25 16:00 ` Kai Huang
2022-05-18 22:30 ` Sagi Shahar
2022-05-18 23:56 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 10/21] x86/virt/tdx: Add placeholder to coveret all system RAM as TDX memory Kai Huang
2022-04-20 20:48 ` Isaku Yamahata
2022-04-20 22:38 ` Kai Huang
2022-04-27 22:24 ` Dave Hansen
2022-04-28 0:53 ` Kai Huang
2022-04-28 1:07 ` Dave Hansen
2022-04-28 1:35 ` Kai Huang
2022-04-28 3:40 ` Dave Hansen
2022-04-28 3:55 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 11/21] x86/virt/tdx: Choose to use " Kai Huang
2022-04-20 20:55 ` Isaku Yamahata
2022-04-20 22:39 ` Kai Huang
2022-04-28 15:54 ` Dave Hansen
2022-04-29 7:32 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 12/21] x86/virt/tdx: Create TDMRs to cover all system RAM Kai Huang
2022-04-28 16:22 ` Dave Hansen
2022-04-29 7:24 ` Kai Huang
2022-04-29 13:52 ` Dave Hansen
2022-04-06 4:49 ` [PATCH v3 13/21] x86/virt/tdx: Allocate and set up PAMTs for TDMRs Kai Huang
2022-04-28 17:12 ` Dave Hansen
2022-04-29 7:46 ` Kai Huang
2022-04-29 14:20 ` Dave Hansen
2022-04-29 14:30 ` Sean Christopherson
2022-04-29 17:46 ` Dave Hansen
2022-04-29 18:19 ` Sean Christopherson
2022-04-29 18:32 ` Dave Hansen
2022-05-02 5:59 ` Kai Huang
2022-05-02 14:17 ` Dave Hansen
2022-05-02 21:55 ` Kai Huang
2022-04-06 4:49 ` [PATCH v3 14/21] x86/virt/tdx: Set up reserved areas for all TDMRs Kai Huang
2022-04-06 4:49 ` [PATCH v3 15/21] x86/virt/tdx: Reserve TDX module global KeyID Kai Huang
2022-04-06 4:49 ` [PATCH v3 16/21] x86/virt/tdx: Configure TDX module with TDMRs and " Kai Huang
2022-04-06 4:49 ` [PATCH v3 17/21] x86/virt/tdx: Configure global KeyID on all packages Kai Huang
2022-04-06 4:49 ` [PATCH v3 18/21] x86/virt/tdx: Initialize all TDMRs Kai Huang
2022-04-06 4:49 ` [PATCH v3 19/21] x86: Flush cache of TDX private memory during kexec() Kai Huang
2022-04-06 4:49 ` [PATCH v3 20/21] x86/virt/tdx: Add kernel command line to opt-in TDX host support Kai Huang
2022-04-28 17:25 ` Dave Hansen
2022-04-06 4:49 ` [PATCH v3 21/21] Documentation/x86: Add documentation for " Kai Huang
2022-04-14 10:19 ` [PATCH v3 00/21] TDX host kernel support Kai Huang
2022-04-26 20:13 ` Dave Hansen
2022-04-27 1:15 ` Kai Huang
2022-04-27 21:59 ` Dave Hansen
2022-04-28 0:37 ` Kai Huang
2022-04-28 0:50 ` Dave Hansen
2022-04-28 0:58 ` Kai Huang
2022-04-29 1:40 ` Kai Huang
2022-04-29 3:04 ` Dan Williams [this message]
2022-04-29 5:35 ` Kai Huang
2022-05-03 23:59 ` Kai Huang
2022-05-04 0:25 ` Dave Hansen
2022-05-04 1:15 ` Kai Huang
2022-05-05 9:54 ` Kai Huang
2022-05-05 13:51 ` Dan Williams
2022-05-05 22:14 ` Kai Huang
2022-05-06 0:22 ` Dan Williams
2022-05-06 0:45 ` Kai Huang
2022-05-06 1:15 ` Dan Williams
2022-05-06 1:46 ` Kai Huang
2022-05-06 15:57 ` Dan Williams
2022-05-09 2:46 ` Kai Huang
2022-05-10 10:25 ` Kai Huang
2022-05-07 0:09 ` Mike Rapoport
2022-05-08 10:00 ` Kai Huang
2022-05-09 10:33 ` Mike Rapoport
2022-05-09 23:27 ` Kai Huang
2022-05-04 14:31 ` Dan Williams
2022-05-04 22:50 ` Kai Huang
2022-04-28 1:01 ` Dan Williams
2022-04-28 1:21 ` Kai Huang
2022-04-29 2:58 ` Dan Williams
2022-04-29 5:43 ` Kai Huang
2022-04-29 14:39 ` Dave Hansen
2022-04-29 15:18 ` Dan Williams
2022-04-29 17:18 ` Dave Hansen
2022-04-29 17:48 ` Dan Williams
2022-04-29 18:34 ` Dave Hansen
2022-04-29 18:47 ` Dan Williams
2022-04-29 19:20 ` Dave Hansen
2022-04-29 21:20 ` Dan Williams
2022-04-29 21:27 ` Dave Hansen
2022-05-02 10:18 ` Kai Huang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAPcyv4gEwjnNE9cWb_KLZ6C7-UxKdUMZKFPF+LAJ4L1SjByisw@mail.gmail.com \
--to=dan.j.williams@intel.com \
--cc=ak@linux.intel.com \
--cc=dave.hansen@intel.com \
--cc=isaku.yamahata@intel.com \
--cc=kai.huang@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kvm@vger.kernel.org \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=reinette.chatre@intel.com \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=seanjc@google.com \
--cc=tony.luck@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).