2022-04-06 13:57:41

by Huang, Kai

Subject: [PATCH v3 20/21] x86/virt/tdx: Add kernel command line to opt-in TDX host support

Enabling TDX consumes additional memory (used by TDX as metadata) and
additional initialization time. Introduce a kernel command line to
allow to opt-in TDX host kernel support when user truly wants to use
TDX.

Signed-off-by: Kai Huang <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
arch/x86/virt/vmx/tdx/tdx.c | 14 ++++++++++++++
2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3f1cc5e317ed..cfa5b36890ea 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5790,6 +5790,12 @@

tdfx= [HW,DRM]

+ tdx_host= [X86-64, TDX]
+ Format: {on|off}
+ on: Enable TDX host kernel support
+ off: Disable TDX host kernel support
+ Default is off.
+
test_suspend= [SUSPEND][,N]
Specify "mem" (for Suspend-to-RAM) or "standby" (for
standby suspend) or "freeze" (for suspend type freeze)
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 031af7b83cea..fee243cd454f 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -116,6 +116,16 @@ static struct tdsysinfo_struct tdx_sysinfo;
/* TDX global KeyID to protect TDX metadata */
static u32 tdx_global_keyid;

+static bool enable_tdx_host;
+
+static int __init tdx_host_setup(char *s)
+{
+ if (!strcmp(s, "on"))
+ enable_tdx_host = true;
+ return 1;
+}
+__setup("tdx_host=", tdx_host_setup);
+
static bool __seamrr_enabled(void)
{
return (seamrr_mask & SEAMRR_ENABLED_BITS) == SEAMRR_ENABLED_BITS;
@@ -500,6 +510,10 @@ static int detect_p_seamldr(void)

static int __tdx_detect(void)
{
+ /* Disabled by kernel command line */
+ if (!enable_tdx_host)
+ goto no_tdx_module;
+
/* The TDX module is not loaded if SEAMRR is disabled */
if (!seamrr_enabled()) {
pr_info("SEAMRR not enabled.\n");
--
2.35.1

2022-05-01 08:21:26

by Dave Hansen

Subject: Re: [PATCH v3 20/21] x86/virt/tdx: Add kernel command line to opt-in TDX host support

On 4/5/22 21:49, Kai Huang wrote:
> Enabling TDX consumes additional memory (used by TDX as metadata) and
> additional initialization time. Introduce a kernel command line to
> allow to opt-in TDX host kernel support when user truly wants to use
> TDX.

From the cover letter:

"This series doesn't initialize TDX at boot time"

Could you please square that circle for me? How does a feature that
doesn't get initialized a boot time need a boot-time command line opt-in?