linux-kernel - [PATCH 04/20] x86/tdx: Convert HLT handling to use new TDVMCALL

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Date: Fri, 17 May 2024 17:19:22 +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 04/20] x86/tdx: Convert HLT handling to use new TDVMCALL_0()

Use newly introduced TDVMCALL_0() instead of __tdx_hypercall() to handle
HLT instruction emulation.

It cuts code bloat substantially:

Function                                     old     new   delta
tdx_safe_halt                                 58      88     +30
tdx_handle_virt_exception                   2023    2052     +29
__pfx___halt                                  16       -     -16
__halt                                       171       -    -171
Total: Before=6350, After=6222, chg -2.02%

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 6e0e5648ebd1..dce7d6f9f895 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -350,18 +350,12 @@ static int ve_instr_len(struct ve_info *ve)
 	}
 }
 
-static u64 __cpuidle __halt(const bool irq_disabled)
+static int handle_halt(struct ve_info *ve)
 {
-	struct tdx_module_args args = {
-		.r10 = TDX_HYPERCALL_STANDARD,
-		.r11 = hcall_func(EXIT_REASON_HLT),
-		.r12 = irq_disabled,
-	};
-
 	/*
 	 * Emulate HLT operation via hypercall. More info about ABI
 	 * can be found in TDX Guest-Host-Communication Interface
-	 * (GHCI), section 3.8 TDG.VP.VMCALL<Instruction.HLT>.
+	 * (GHCI), section TDG.VP.VMCALL<Instruction.HLT>.
 	 *
 	 * The VMM uses the "IRQ disabled" param to understand IRQ
 	 * enabled status (RFLAGS.IF) of the TD guest and to determine
@@ -370,14 +364,7 @@ static u64 __cpuidle __halt(const bool irq_disabled)
 	 * can keep the vCPU in virtual HLT, even if an IRQ is
 	 * pending, without hanging/breaking the guest.
 	 */
-	return __tdx_hypercall(&args);
-}
-
-static int handle_halt(struct ve_info *ve)
-{
-	const bool irq_disabled = irqs_disabled();
-
-	if (__halt(irq_disabled))
+	if (TDVMCALL_0(hcall_func(EXIT_REASON_HLT), irqs_disabled(), 0, 0, 0))
 		return -EIO;
 
 	return ve_instr_len(ve);
@@ -385,13 +372,9 @@ static int handle_halt(struct ve_info *ve)
 
 void __cpuidle tdx_safe_halt(void)
 {
-	const bool irq_disabled = false;
-
-	/*
-	 * Use WARN_ONCE() to report the failure.
-	 */
-	if (__halt(irq_disabled))
-		WARN_ONCE(1, "HLT instruction emulation failed\n");
+	/* See comment in handle_halt() */
+	WARN_ONCE(TDVMCALL_0(hcall_func(EXIT_REASON_HLT), false, 0, 0, 0),
+		  "HLT instruction emulation failed");
 }
 
 static int read_msr(struct pt_regs *regs, struct ve_info *ve)
-- 
2.43.0