linux-kernel - [tip: sched/core] cpuidle, tdx: Make TDX code noinstr clean

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Date:   Fri, 13 Jan 2023 12:31:09 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Frederic Weisbecker <frederic@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] cpuidle, tdx: Make TDX code noinstr clean

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     c3982c1a36f70bd4521a9852246ea50105912084
Gitweb:        https://git.kernel.org/tip/c3982c1a36f70bd4521a9852246ea50105912084
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 12 Jan 2023 20:43:43 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 13 Jan 2023 11:48:16 +01:00

cpuidle, tdx: Make TDX code noinstr clean

objtool found a few cases where this code called out into instrumented
code:

  vmlinux.o: warning: objtool: __halt+0x2c: call to hcall_func.constprop.0() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __halt+0x3f: call to __tdx_hypercall() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __tdx_hypercall+0x66: call to __tdx_hypercall_failed() leaves .noinstr.text section

Fix it by:

  - moving TDX tdcall assembly methods into .noinstr.text (they are already noistr-clean)
  - marking __tdx_hypercall_failed() as 'noinstr'
  - annotating hcall_func() as __always_inline

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Tony Lindgren <tony@...mide.com>
Tested-by: Ulf Hansson <ulf.hansson@...aro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Acked-by: Frederic Weisbecker <frederic@...nel.org>
Link: https://lore.kernel.org/r/20230112195541.111485720@infradead.org
---
 arch/x86/boot/compressed/vmlinux.lds.S | 1 +
 arch/x86/coco/tdx/tdcall.S             | 2 ++
 arch/x86/coco/tdx/tdx.c                | 5 +++--
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 112b237..b22f34b 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -34,6 +34,7 @@ SECTIONS
 		_text = .; 	/* Text */
 		*(.text)
 		*(.text.*)
+		*(.noinstr.text)
 		_etext = . ;
 	}
 	.rodata : {
diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 508c173..ad0d51f 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -31,6 +31,8 @@
 					  TDX_R12 | TDX_R13 | \
 					  TDX_R14 | TDX_R15 )
 
+.section .noinstr.text, "ax"
+
 /*
  * __tdx_module_call()  - Used by TDX guests to request services from
  * the TDX module (does not include VMM services) using TDCALL instruction.
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 8804174..70e8015 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -64,8 +64,9 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
 }
 
 /* Called from __tdx_hypercall() for unrecoverable failure */
-void __tdx_hypercall_failed(void)
+noinstr void __tdx_hypercall_failed(void)
 {
+	instrumentation_begin();
 	panic("TDVMCALL failed. TDX module bug?");
 }
 
@@ -75,7 +76,7 @@ void __tdx_hypercall_failed(void)
  * Reusing the KVM EXIT_REASON macros makes it easier to connect the host and
  * guest sides of these calls.
  */
-static u64 hcall_func(u64 exit_reason)
+static __always_inline u64 hcall_func(u64 exit_reason)
 {
 	return exit_reason;
 }