linux-kernel - [PATCH 05/20] x86/tdx: Convert MSR read handling to use new TDVMCALL

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Date: Fri, 17 May 2024 17:19:23 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc: linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 05/20] x86/tdx: Convert MSR read handling to use new TDVMCALL_1()

Use newly introduced TDVMCALL_1() instead of __tdx_hypercall() to handle
MSR read emulation.

It cuts code bloat substantially:

Function                                     old     new   delta
tdx_handle_virt_exception                   2052    1947    -105

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 15 +++++++--------
 arch/x86/hyperv/ivm.c   | 10 ++--------
 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index dce7d6f9f895..32c519d096de 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -379,22 +379,21 @@ void __cpuidle tdx_safe_halt(void)
 
 static int read_msr(struct pt_regs *regs, struct ve_info *ve)
 {
-	struct tdx_module_args args = {
-		.r10 = TDX_HYPERCALL_STANDARD,
-		.r11 = hcall_func(EXIT_REASON_MSR_READ),
-		.r12 = regs->cx,
-	};
+	u64 val;
 
 	/*
 	 * Emulate the MSR read via hypercall. More info about ABI
 	 * can be found in TDX Guest-Host-Communication Interface
 	 * (GHCI), section titled "TDG.VP.VMCALL<Instruction.RDMSR>".
 	 */
-	if (__tdx_hypercall(&args))
+	if (TDVMCALL_1(hcall_func(EXIT_REASON_MSR_READ),
+		       regs->cx, 0, 0, 0, val)) {
 		return -EIO;
+	}
+
+	regs->ax = lower_32_bits(val);
+	regs->dx = upper_32_bits(val);
 
-	regs->ax = lower_32_bits(args.r11);
-	regs->dx = upper_32_bits(args.r11);
 	return ve_instr_len(ve);
 }
 
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index b4a851d27c7c..3e2cbfb2203d 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -399,18 +399,12 @@ static void hv_tdx_msr_write(u64 msr, u64 val)
 
 static void hv_tdx_msr_read(u64 msr, u64 *val)
 {
-	struct tdx_module_args args = {
-		.r10 = TDX_HYPERCALL_STANDARD,
-		.r11 = EXIT_REASON_MSR_READ,
-		.r12 = msr,
-	};
+	u64 ret;
 
-	u64 ret = __tdx_hypercall(&args);
+	ret = TDVMCALL_1(hcall_func(EXIT_REASON_MSR_READ), msr, 0, 0, 0, *val);
 
 	if (WARN_ONCE(ret, "Failed to emulate MSR read: %lld\n", ret))
 		*val = 0;
-	else
-		*val = args.r11;
 }
 
 u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
-- 
2.43.0