On 11/6/22 11:50, Borislav Petkov wrote: > On Sun, Nov 06, 2022 at 09:02:27AM -0800, Dave Hansen wrote: >> It's fine for now, except that the naming on this: >> >> - tdx_parse_tdinfo(&cc_mask); >> + cc_mask = tdx_parse_tdinfo(); >> >> is a bit funky since tdx_parse_tdinfo() is doing a couple of things > Yeah, that was the next thing that was bothering me. > >> and will need to return a second item shortly. > Well, then rename this one back to get_cc_mask() and have a new function > return the second item? That's doable. It would look something like what I've attached for now. The only downside to this is making two tdx_module_call(TDX_GET_INFO...) calls. That seems a bit wasteful, but it's not the end of the world. It would look something like the attached patch. I kinda like the idea of making one tdx_module_call() and parsing it all in one place. The calls are kinda slow, but two of them versus one isn't going to hurt anybody. The other thing I considered was keeping a temporary 'struct tdx_guest_info' structure or something, filling it one, and parsing it in get_cc_mask() and attribute checking functions. But, that seemed like overkill.
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index b8998cf0508a..a4bf2b67d3d7 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -13,7 +13,7 @@
#include <asm/pgtable.h>
/* TDX module Call Leaf IDs */
-#define TDX_GET_INFO 1
+#define TDX_GET_INFO 1 /* TDG.VP.INFO */
#define TDX_GET_VEINFO 3
#define TDX_ACCEPT_PAGE 6
@@ -100,19 +100,10 @@ static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
}
-static void tdx_parse_tdinfo(u64 *cc_mask)
+static u64 get_cc_mask(void)
{
struct tdx_module_output out;
- unsigned int gpa_width;
- u64 td_attr;
- /*
- * TDINFO TDX module call is used to get the TD execution environment
- * information like GPA width, number of available vcpus, debug mode
- * information, etc. More details about the ABI can be found in TDX
- * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
- * [TDG.VP.INFO].
- */
tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out);
/*
@@ -123,7 +114,15 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
* can not meaningfully run without it.
*/
gpa_width = out.rcx & GENMASK(5, 0);
- *cc_mask = BIT_ULL(gpa_width - 1);
+ return BIT_ULL(gpa_width - 1);
+}
+
+static void tdx_check_tdinfo(void)
+{
+ struct tdx_module_output out;
+ u64 td_attr;
+
+ tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out);
/*
* The kernel can not handle #VE's when accessing normal kernel
@@ -769,7 +768,8 @@ void __init tdx_early_init(void)
setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
cc_set_vendor(CC_VENDOR_INTEL);
- tdx_parse_tdinfo(&cc_mask);
+ tdx_check_tdinfo();
+ cc_mask = get_cc_mask();
cc_set_mask(cc_mask);
/*
|