linux-kernel - [PATCH 1/4] x86/tdx: Introduce tdg_vm

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Date: Sat,  9 Mar 2024 23:02:27 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...el.com
Cc: sathyanarayanan.kuppuswamy@...ux.intel.com,
	hpa@...or.com,
	seanjc@...gle.com,
	ele.reshetova@...el.com,
	rick.p.edgecombe@...el.com,
	x86@...nel.org,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 1/4] x86/tdx: Introduce tdg_vm_wr()

Add a helper to write to a TD-scope metadata field and use it to set
NOTIFY_ENABLES.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index cc67f7380055..5ffe5ef99536 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -77,6 +77,20 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args)
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
+static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
+{
+	struct tdx_module_args args = {
+		.rdx = field,
+		.r8 = value,
+		.r9 = mask,
+	};
+
+	tdcall(TDG_VM_WR, &args);
+
+	/* Old value */
+	return args.r8;
+}
+
 /**
  * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
  *                           subtype 0) using TDG.MR.REPORT TDCALL.
@@ -902,10 +916,6 @@ static void tdx_kexec_unshare_mem(void)
 
 void __init tdx_early_init(void)
 {
-	struct tdx_module_args args = {
-		.rdx = TDCS_NOTIFY_ENABLES,
-		.r9 = -1ULL,
-	};
 	u64 cc_mask;
 	u32 eax, sig[3];
 
@@ -924,7 +934,7 @@ void __init tdx_early_init(void)
 	cc_set_mask(cc_mask);
 
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdcall(TDG_VM_WR, &args);
+	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
-- 
2.43.0