Re: [PATCH] x86/kvm/tdx: Save %rbp in TDX_MODULE_CALL

["Huang, Kai" <kai.huang@intel.com>]

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On Thu, 2024-05-23 at 10:30 +0000, Huang, Kai wrote:
> On Thu, 2024-05-23 at 07:56 +0200, Jürgen Groß wrote:
> > On 20.05.24 13:54, Huang, Kai wrote:
> > > On Fri, 2024-05-17 at 09:48 -0700, Dave Hansen wrote:
> > > > On 5/17/24 08:58, Juergen Gross wrote:
> > > > > On 17.05.24 17:52, Dave Hansen wrote:
> > > > ..
> > > > > > Once we have the specific TDX module version, we can go ask the folks
> > > > > > who write it if there were any RBP clobbering bugs.
> > > > > 
> > > > > Okay, how to get the TDX module version?
> > > > 
> > > > You need something like this:
> > > > 
> > > > > https://lore.kernel.org/all/20231012134136.1310650-1-yi.sun@intel.com/
> > > 
> > > This one prints TDX version info in the TDX guest, but not host.
> > > 
> > > The attached diff prints the TDX version (something like below) during
> > > module initialization, and should meet Juergen's needs for temporary use:
> > > 
> > > [  113.543538] virt/tdx: module verson: major 1, minor 5, internal 0
> > > 
> > > > 
> > > > .. and yeah, this needs to be upstream.
> > > > 
> > > 
> > >  From this thread I think it makes sense to add code to the TDX host code
> > > to print the TDX version during module initialization.  I'll start to work
> > > on this.
> > > 
> > > One thing is from the spec TDX has "4 versions": major, minor, update,
> > > internal.  They are all 16-bit, and the overall version can be written in:
> > > 
> > > 	<Major>.<Minor>.<Update>.<Internal>, e.g., 1.5.05.01
> > > 
> > > (see TDX module 1.5 API spec, section 3.3.2 "TDX Module Version".)
> > > 
> > > The attached diff only prints major, minor and internal, but leaves the
> > > update out because I believe it is for module runtime update (yet to
> > > confirm).
> > > 
> > > Given there are 4 versions, I think it makes sense to implement reading
> > > them based on this patchset ...
> > > 
> > > https://lore.kernel.org/kvm/6940c326-bfca-4c67-badf-ab5c086bf492@intel.com/T/
> > > 
> > > ... which extends the global metadata reading code to support any
> > > arbitrary struct and all element sizes (although all 4 versions are 16-
> > > bit)?
> > 
> > With that I got:
> > 
> > [   29.328484] virt/tdx: module verson: major 1, minor 5, internal 0
> > 
> > 
> 
> Let me check TDX module guys on this and get back to you.

Hi Jurgen,

I was told the module starting with "1.5.06." has NO_RBP_MOD support.

And I think I was wrong about the <update> part of the version, and we
need that to determine the third part of the module version.

I was also told the 1.5.06 module hasn't been released to public yet, so I
guess your module doesn't support it.

I did another patch (attached) to check NO_RBP_MOD and reject module
initialization if it is not supported, and print out module version:

[  146.566641] virt/tdx: NO_RBP_MOD feature is not supported
[  146.572797] virt/tdx: module verson: 1.5.0.0
[  146.577731] virt/tdx: module initialization failed (-22)

You can have another try to verify at your side, if that helps.


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commit e3907269b34e4f488284f35716f231da7bc3e6b3
Author: Kai Huang <kai.huang@intel.com>
Date:   Thu May 23 23:17:28 2024 +1200

    x86/virt/tdx: check NO_RBP_MOD and print module version
    
    Signed-off-by: Kai Huang <kai.huang@intel.com>

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 4d6826a76f78..ffc1c27b9134 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1097,11 +1097,60 @@ static int init_tdmrs(struct tdmr_info_list *tdmr_list)
 	return 0;
 }
 
+static int check_module_compatibility(void)
+{
+	u64 tdx_features0;
+	int ret;
+
+	ret = read_sys_metadata_field(MD_FIELD_ID_TDX_FEATURES0,
+			&tdx_features0);
+
+	if (ret)
+		return ret;
+
+	if (!(tdx_features0 & TDX_FEATURES0_NO_RBP_MOD)) {
+		pr_err("NO_RBP_MOD feature is not supported\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void print_tdx_version(void)
+{
+	u64 major, minor, update, internal;
+	int ret;
+
+	ret = read_sys_metadata_field(MD_FIELD_ID_MAJOR_VERSION, &major);
+	if (ret)
+		return;
+
+	ret = read_sys_metadata_field(MD_FIELD_ID_MINOR_VERSION, &minor);
+	if (ret)
+		return;
+
+	ret = read_sys_metadata_field(MD_FIELD_ID_UPDATE_VERSION, &update);
+	if (ret)
+		return;
+
+	ret = read_sys_metadata_field(MD_FIELD_ID_INTERNAL_VERSION, &internal);
+	if (ret)
+		return;
+
+	pr_info("module verson: %u.%u.%u.%u\n",
+			(u16)major, (u16)minor, (u16)update, (u16)internal);
+}
+
 static int init_tdx_module(void)
 {
 	struct tdx_tdmr_sysinfo tdmr_sysinfo;
 	int ret;
 
+	/* Make sure TDX module meets kernel's expectation */
+	ret = check_module_compatibility();
+	if (ret)
+		goto out;
+
 	/*
 	 * To keep things simple, assume that all TDX-protected memory
 	 * will come from the page allocator.  Make sure all pages in the
@@ -1155,6 +1204,10 @@ static int init_tdx_module(void)
 	 * Lock out memory hotplug code while building it.
 	 */
 	put_online_mems();
+
+out:
+	print_tdx_version();
+
 	return ret;
 
 err_reset_pamts:
diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
index b701f69485d3..13ad52352e35 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -37,6 +37,14 @@
 #define MD_FIELD_ID_PAMT_2M_ENTRY_SIZE		0x9100000100000011ULL
 #define MD_FIELD_ID_PAMT_1G_ENTRY_SIZE		0x9100000100000012ULL
 
+#define MD_FIELD_ID_TDX_FEATURES0		0x0A00000300000008ULL
+#define TDX_FEATURES0_NO_RBP_MOD		BIT_ULL(18)
+
+#define MD_FIELD_ID_MINOR_VERSION		0x0800000100000003ULL
+#define MD_FIELD_ID_MAJOR_VERSION		0x0800000100000004ULL
+#define MD_FIELD_ID_UPDATE_VERSION		0x0800000100000005ULL
+#define MD_FIELD_ID_INTERNAL_VERSION		0x0800000100000006ULL
+
 /*
  * Sub-field definition of metadata field ID.
  *