Re: [PATCH v2 3/5] x86/virt/tdx: Detect if the extensions initialization is required

[Xu Yilun]

On Mon, Sep 28, 2026 at 09:06:15PM +0000, Edgecombe, Rick P wrote:
> On Tue, 2026-09-15 at 14:14 -0700, Rick Edgecombe wrote:
> > now that we don't need to do this on update
> 
> Per an off-list discussion, we agreed to not have TDH.SYS.UPDATE do the
> TDH.EXT.INIT work internally so  that another VMM can have more flexibility. So
> we now need to go back to something like we had in v1 where it is called after
> update. But given the change in error codes for TDH.EXT.INIT, I think we still
> don't need to save the ext_required metadata field? We can just call it
> unconditionally, right?

right.

> So it should still be a bit simpler than v1.

Another thing is about the addon_features0 argument for TDH.SYS.UPDATE.
In v1 -> v2, in order to meet the goal of "just restore everything that
was configured during boot", this bitmap argument is removed. I think
this argument removal is orthogonal to the TDH.EXT.INIT discussion and
still has merit.

  TDH.SYS.UPDATE(v0): TDX module reconfigures same features as specified by
		      TDH.SYS.CONFIG, Linux would use this SEAMCALL version.

  TDH.SYS.UPDATE(v1, addon_featues0): VMM can configure new features specified
				      by addon_features0 argument. For other VMM.

Then we can just add one patch based on v2 series:

----8<----

    x86/virt/tdx: Re-initialize the extensions on runtime TDX module update

    xxxxx

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index c28e65f56532..8d737b86a1d6 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1309,7 +1309,7 @@ static __init int tdx_ext_mem_setup(void)
        return ret;
 }

-static __init int tdx_ext_init(void)
+static int tdx_ext_init(void)
 {
        struct tdx_module_args args = {};
        u64 ret;
@@ -1340,6 +1340,19 @@ static __init int init_tdx_module_extensions(void)
        return tdx_ext_init();
 }

+/*
+ * Don't update the memory requirement or try memory allocation in
+ * stop_machine(). If an incompatible update requires more memory, let the
+ * extensions re-initialization fail.
+ */
+static int reinit_tdx_module_extensions(void)
+{
+       if (!(tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_EXT))
+               return 0;
+
+       return tdx_ext_init();
+}
+
 static __init int init_tdx_module(void)
 {
        int ret;
@@ -1517,6 +1530,10 @@ int tdx_module_run_update(void)
        if (ret)
                return ret;

+       ret = reinit_tdx_module_extensions();
+       if (ret)
+               return ret;
+
        ret = get_tdx_sys_info_version(&tdx_sysinfo.version);
        /*
         * Only fails if there is something unexpected