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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@infradead.org>
AuthorDate: Thu, 12 Jan 2023 20:43:43 +01:00
Committer: Ingo Molnar <mingo@kernel.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@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.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;
}
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