From: Kai Huang <kai.huang@intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: seanjc@google.com, pbonzini@redhat.com, len.brown@intel.com,
tony.luck@intel.com, rafael.j.wysocki@intel.com,
reinette.chatre@intel.com, dan.j.williams@intel.com,
peterz@infradead.org, ak@linux.intel.com,
kirill.shutemov@linux.intel.com,
sathyanarayanan.kuppuswamy@linux.intel.com,
isaku.yamahata@intel.com
Subject: Re: [PATCH v3 03/21] x86/virt/tdx: Implement the SEAMCALL base function
Date: Wed, 27 Apr 2022 11:29:39 +1200 [thread overview]
Message-ID: <de53b1ddea591e2a6fc8ac0510e3ab59f5f58512.camel@intel.com> (raw)
In-Reply-To: <56f368c6-4a60-ea78-2cc7-cd2d57823e3a@intel.com>
On Tue, 2022-04-26 at 13:37 -0700, Dave Hansen wrote:
> On 4/5/22 21:49, Kai Huang wrote:
> > Secure Arbitration Mode (SEAM) is an extension of VMX architecture. It
> > defines a new VMX root operation (SEAM VMX root) and a new VMX non-root
> > operation (SEAM VMX non-root) which are isolated from legacy VMX root
> > and VMX non-root mode.
>
> I feel like this is too much detail for an opening paragraph.
>
> > A CPU-attested software module (called the 'TDX module') runs in SEAM
> > VMX root to manage the crypto-protected VMs running in SEAM VMX non-root.
> > SEAM VMX root is also used to host another CPU-attested software module
> > (called the 'P-SEAMLDR') to load and update the TDX module.
> > > Host kernel transits to either the P-SEAMLDR or the TDX module via the
> > new SEAMCALL instruction. SEAMCALL leaf functions are host-side
> > interface functions defined by the P-SEAMLDR and the TDX module around
> > the new SEAMCALL instruction. They are similar to a hypercall, except
> > they are made by host kernel to the SEAM software.
>
> I think you can get rid of about half of this changelog so farand make
> it more clear in the process with this:
>
> TDX introduces a new CPU mode: Secure Arbitration Mode (SEAM).
> This mode runs only the TDX module itself or other code needed
> to load the TDX module.
>
> The host kernel communicates with SEAM software via a new
> SEAMCALL instruction. This is conceptually similar to
> a guest->host hypercall, except it is made from the host to SEAM
> software instead.
Thank you!
>
> This is a technical document, but you're writing too technically for my
> taste and focusing on the low-level details rather than the high-level
> concepts. What do I care that SEAM is two modes and what their names
> are at this juncture? Are those details necesarry to get me to
> understand what a SEAMCALL is or what this patch implements?
Thanks for the point. I'll revisit this series based on this in next version.
>
> > SEAMCALL leaf functions use an ABI different from the x86-64 system-v
> > ABI. Instead, they share the same ABI with the TDCALL leaf functions.
> > %rax is used to carry both the SEAMCALL leaf function number (input) and
> > the completion status code (output). Additional GPRs (%rcx, %rdx,
> > %r8->%r11) may be further used as both input and output operands in
> > individual leaf functions.
> >
> > Implement a C function __seamcall()
>
> Your "C function" looks a bit like assembly to me.
Will change to (I saw TDX guest patch used similar way):
Add a generic interface to do SEAMCALL leaf functions, using the
assembly macro used by __tdx_module_call().
>
> > to do SEAMCALL leaf functions using
> > the assembly macro used by __tdx_module_call() (the implementation of
> > TDCALL leaf functions). The only exception not covered here is TDENTER
> > leaf function which takes all GPRs and XMM0-XMM15 as both input and
> > output. The caller of TDENTER should implement its own logic to call
> > TDENTER directly instead of using this function.
>
> I have no idea why this paragraph is here or what it is trying to tell me.
Will get rid of the rest staff.
>
> > SEAMCALL instruction is essentially a VMExit from VMX root to SEAM VMX
> > root, and it can fail with VMfailInvalid, for instance, when the SEAM
> > software module is not loaded. The C function __seamcall() returns
> > TDX_SEAMCALL_VMFAILINVALID, which doesn't conflict with any actual error
> > code of SEAMCALLs, to uniquely represent this case.
>
> Again, I'm lost. Why is this detail here? I don't even see
> TDX_SEAMCALL_VMFAILINVALID in the patch.
Will remove.
>
> > diff --git a/arch/x86/virt/vmx/tdx/Makefile b/arch/x86/virt/vmx/tdx/Makefile
> > index 1bd688684716..fd577619620e 100644
> > --- a/arch/x86/virt/vmx/tdx/Makefile
> > +++ b/arch/x86/virt/vmx/tdx/Makefile
> > @@ -1,2 +1,2 @@
> > # SPDX-License-Identifier: GPL-2.0-only
> > -obj-$(CONFIG_INTEL_TDX_HOST) += tdx.o
> > +obj-$(CONFIG_INTEL_TDX_HOST) += tdx.o seamcall.o
> > diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
> > new file mode 100644
> > index 000000000000..327961b2dd5a
> > --- /dev/null
> > +++ b/arch/x86/virt/vmx/tdx/seamcall.S
> > @@ -0,0 +1,52 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#include <linux/linkage.h>
> > +#include <asm/frame.h>
> > +
> > +#include "tdxcall.S"
> > +
> > +/*
> > + * __seamcall() - Host-side interface functions to SEAM software module
> > + * (the P-SEAMLDR or the TDX module)
> > + *
> > + * Transform function call register arguments into the SEAMCALL register
> > + * ABI. Return TDX_SEAMCALL_VMFAILINVALID, or the completion status of
> > + * the SEAMCALL. Additional output operands are saved in @out (if it is
> > + * provided by caller).
>
> This needs to say:
>
> Returns TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself fails.
OK.
--
Thanks,
-Kai
next prev parent reply other threads:[~2022-04-26 23:29 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 [this message]
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
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
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