linux-kernel - [PATCH 1/2] x86/tdx: Extract GET_INFO call from get_cc

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Date:   Fri, 28 Oct 2022 17:12:19 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, ak@...ux.intel.com,
        dan.j.williams@...el.com, david@...hat.com, hpa@...or.com,
        seanjc@...gle.com, thomas.lendacky@....com,
        elena.reshetova@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 1/2] x86/tdx: Extract GET_INFO call from get_cc_mask()

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

TDCALL [TDG.VP.INFO] is used to get details like gpa_width,
TD attributes, etc.

So far only gpa_width was needed to enumerate the shared bit, but
upcoming changes will need TD attributes too.

Extract GET_INFO call out of get_cc_mask() into a separate helper and
save attributes.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 928dcf7a20d9..343d60853b71 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -34,6 +34,12 @@
 #define VE_GET_PORT_NUM(e)	((e) >> 16)
 #define VE_IS_IO_STRING(e)	((e) & BIT(4))
 
+/* Caches GPA width from TDG.VP.INFO TDCALL */
+static unsigned int gpa_width __ro_after_init;
+
+/* Caches TD Attributes from TDG.VP.INFO TDCALL */
+static u64 td_attr __ro_after_init;
+
 /*
  * Wrapper for standard use of __tdx_hypercall with no output aside from
  * return code.
@@ -98,17 +104,16 @@ 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 u64 get_cc_mask(void)
+static void tdx_parse_tdinfo(void)
 {
 	struct tdx_module_output out;
-	unsigned int gpa_width;
 
 	/*
 	 * 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].
+	 * information, TD attributes etc. More details about the ABI can be
+	 * found in TDX Guest-Host-Communication Interface (GHCI), section
+	 * 2.4.2 TDCALL [TDG.VP.INFO].
 	 *
 	 * The GPA width that comes out of this call is critical. TDX guests
 	 * can not meaningfully run without it.
@@ -116,7 +121,11 @@ static u64 get_cc_mask(void)
 	tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out);
 
 	gpa_width = out.rcx & GENMASK(5, 0);
+	td_attr = out.rdx;
+}
 
+static u64 get_cc_mask(void)
+{
 	/*
 	 * The highest bit of a guest physical address is the "sharing" bit.
 	 * Set it for shared pages and clear it for private pages.
@@ -755,6 +764,12 @@ void __init tdx_early_init(void)
 	if (memcmp(TDX_IDENT, sig, sizeof(sig)))
 		return;
 
+	/*
+	 * Initializes gpa_width and td_attr. Must be called before
+	 * get_cc_mask() or attribute checks.
+	 */
+	tdx_parse_tdinfo();
+
 	setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
 
 	cc_set_vendor(CC_VENDOR_INTEL);
-- 
2.38.0