linux-kernel - [PATCH V4 48/50] x86/entry: Remove the unused ASM macros

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Date:   Tue, 26 Oct 2021 22:38:46 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Lai Jiangshan <laijs@...ux.alibaba.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH V4 48/50] x86/entry: Remove the unused ASM macros

From: Lai Jiangshan <laijs@...ux.alibaba.com>

They are implemented and used in C code.  The ASM version is not needed
any more.

FENCE_SWAPGS_USER_ENTRY is not removed because it is still being used
in the nmi userspace path.  It could be possible to be removed in
future entry code enhancement.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 arch/x86/entry/calling.h | 99 ----------------------------------------
 1 file changed, 99 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 9065c31d2875..d42012fc694d 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -210,53 +210,6 @@ For 32-bit we have the following conventions - kernel is built with
 	popq	%rax
 .endm
 
-.macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
-	ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI
-	movq	%cr3, \scratch_reg
-	movq	\scratch_reg, \save_reg
-	/*
-	 * Test the user pagetable bit. If set, then the user page tables
-	 * are active. If clear CR3 already has the kernel page table
-	 * active.
-	 */
-	bt	$PTI_USER_PGTABLE_BIT, \scratch_reg
-	jnc	.Ldone_\@
-
-	ADJUST_KERNEL_CR3 \scratch_reg
-	movq	\scratch_reg, %cr3
-
-.Ldone_\@:
-.endm
-
-.macro RESTORE_CR3 scratch_reg:req save_reg:req
-	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
-
-	/* No need to restore when the saved CR3 is kernel CR3. */
-	bt	$PTI_USER_PGTABLE_BIT, \save_reg
-	jnc	.Lend_\@
-
-	ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID
-
-	/*
-	 * Check if there's a pending flush for the user ASID we're
-	 * about to set.
-	 */
-	movq	\save_reg, \scratch_reg
-	andq	$(0x7FF), \scratch_reg
-	bt	\scratch_reg, THIS_CPU_user_pcid_flush_mask
-	jnc	.Lnoflush_\@
-
-	btr	\scratch_reg, THIS_CPU_user_pcid_flush_mask
-	jmp	.Lwrcr3_\@
-
-.Lnoflush_\@:
-	SET_NOFLUSH_BIT \save_reg
-
-.Lwrcr3_\@:
-	movq	\save_reg, %cr3
-.Lend_\@:
-.endm
-
 #else /* CONFIG_PAGE_TABLE_ISOLATION=n: */
 
 .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
@@ -265,10 +218,6 @@ For 32-bit we have the following conventions - kernel is built with
 .endm
 .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req
 .endm
-.macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
-.endm
-.macro RESTORE_CR3 scratch_reg:req save_reg:req
-.endm
 
 #endif
 
@@ -277,17 +226,10 @@ For 32-bit we have the following conventions - kernel is built with
  *
  * FENCE_SWAPGS_USER_ENTRY is used in the user entry swapgs code path, to
  * prevent a speculative swapgs when coming from kernel space.
- *
- * FENCE_SWAPGS_KERNEL_ENTRY is used in the kernel entry non-swapgs code path,
- * to prevent the swapgs from getting speculatively skipped when coming from
- * user space.
  */
 .macro FENCE_SWAPGS_USER_ENTRY
 	ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_USER
 .endm
-.macro FENCE_SWAPGS_KERNEL_ENTRY
-	ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_KERNEL
-.endm
 
 .macro STACKLEAK_ERASE_NOCLOBBER
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
@@ -297,12 +239,6 @@ For 32-bit we have the following conventions - kernel is built with
 #endif
 .endm
 
-.macro SAVE_AND_SET_GSBASE scratch_reg:req save_reg:req
-	rdgsbase \save_reg
-	GET_PERCPU_BASE \scratch_reg
-	wrgsbase \scratch_reg
-.endm
-
 #else /* CONFIG_X86_64 */
 # undef		UNWIND_HINT_IRET_REGS
 # define	UNWIND_HINT_IRET_REGS
@@ -313,38 +249,3 @@ For 32-bit we have the following conventions - kernel is built with
 	call stackleak_erase
 #endif
 .endm
-
-#ifdef CONFIG_SMP
-
-/*
- * CPU/node NR is loaded from the limit (size) field of a special segment
- * descriptor entry in GDT.
- */
-.macro LOAD_CPU_AND_NODE_SEG_LIMIT reg:req
-	movq	$__CPUNODE_SEG, \reg
-	lsl	\reg, \reg
-.endm
-
-/*
- * Fetch the per-CPU GSBASE value for this processor and put it in @reg.
- * We normally use %gs for accessing per-CPU data, but we are setting up
- * %gs here and obviously can not use %gs itself to access per-CPU data.
- *
- * Do not use RDPID, because KVM loads guest's TSC_AUX on vm-entry and
- * may not restore the host's value until the CPU returns to userspace.
- * Thus the kernel would consume a guest's TSC_AUX if an NMI arrives
- * while running KVM's run loop.
- */
-.macro GET_PERCPU_BASE reg:req
-	LOAD_CPU_AND_NODE_SEG_LIMIT \reg
-	andq	$VDSO_CPUNODE_MASK, \reg
-	movq	__per_cpu_offset(, \reg, 8), \reg
-.endm
-
-#else
-
-.macro GET_PERCPU_BASE reg:req
-	movq	pcpu_unit_offsets(%rip), \reg
-.endm
-
-#endif /* CONFIG_SMP */
-- 
2.19.1.6.gb485710b