Commit f49ecf5e authored by H. Peter Anvin's avatar H. Peter Anvin Committed by Dave Hansen
Browse files

x86/cpufeature: Replace X86_FEATURE_SYSENTER32 with X86_FEATURE_SYSFAST32 



In most cases, the use of "fast 32-bit system call" depends either on
X86_FEATURE_SEP or X86_FEATURE_SYSENTER32 || X86_FEATURE_SYSCALL32.
However, nearly all the logic for both is identical.

Define X86_FEATURE_SYSFAST32 which indicates that *either* SYSENTER32 or
SYSCALL32 should be used, for either 32- or 64-bit kernels.  This
defaults to SYSENTER; use SYSCALL if the SYSCALL32 bit is also set.

As this removes ALL existing uses of X86_FEATURE_SYSENTER32, which is
a kernel-only synthetic feature bit, simply remove it and replace it
with X86_FEATURE_SYSFAST32.

This leaves an unused alternative for a true 32-bit kernel, but that
should really not matter in any way.

The clearing of X86_FEATURE_SYSCALL32 can be removed once the patches
for automatically clearing disabled features has been merged.

Signed-off-by: default avatarH. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20251216212606.1325678-10-hpa@zytor.com
parent a0636d4c

arch/x86/Kconfig.cpufeatures

+8 −0
Original line number Diff line number Diff line
@@ -56,6 +56,10 @@ config X86_REQUIRED_FEATURE_MOVBE 
	def_bool y

	depends on MATOM



config X86_REQUIRED_FEATURE_SYSFAST32

	def_bool y

	depends on X86_64 && !X86_FRED



config X86_REQUIRED_FEATURE_CPUID

	def_bool y

	depends on X86_64
@@ -120,6 +124,10 @@ config X86_DISABLED_FEATURE_CENTAUR_MCR 
	def_bool y

	depends on X86_64



config X86_DISABLED_FEATURE_SYSCALL32

	def_bool y

	depends on !X86_64



config X86_DISABLED_FEATURE_PCID

	def_bool y

	depends on !X86_64

arch/x86/entry/vdso/vdso32/system_call.S

+2 −6
Original line number Diff line number Diff line
@@ -52,13 +52,9 @@ __kernel_vsyscall: 
	#define SYSENTER_SEQUENCE	"movl %esp, %ebp; sysenter"

	#define SYSCALL_SEQUENCE	"movl %ecx, %ebp; syscall"



#ifdef BUILD_VDSO32_64

	/* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */

	ALTERNATIVE_2 "", SYSENTER_SEQUENCE, X86_FEATURE_SYSENTER32, \

	ALTERNATIVE_2 "", SYSENTER_SEQUENCE, X86_FEATURE_SYSFAST32, \

			  SYSCALL_SEQUENCE,  X86_FEATURE_SYSCALL32

#else

	ALTERNATIVE "", SYSENTER_SEQUENCE, X86_FEATURE_SEP

#endif



	/* Enter using int $0x80 */

	int	$0x80

arch/x86/include/asm/cpufeatures.h

+1 −1
Original line number Diff line number Diff line
@@ -84,7 +84,7 @@ 
#define X86_FEATURE_PEBS		( 3*32+12) /* "pebs" Precise-Event Based Sampling */

#define X86_FEATURE_BTS			( 3*32+13) /* "bts" Branch Trace Store */

#define X86_FEATURE_SYSCALL32		( 3*32+14) /* syscall in IA32 userspace */

#define X86_FEATURE_SYSENTER32		( 3*32+15) /* sysenter in IA32 userspace */

#define X86_FEATURE_SYSFAST32		( 3*32+15) /* sysenter/syscall in IA32 userspace */

#define X86_FEATURE_REP_GOOD		( 3*32+16) /* "rep_good" REP microcode works well */

#define X86_FEATURE_AMD_LBR_V2		( 3*32+17) /* "amd_lbr_v2" AMD Last Branch Record Extension Version 2 */

#define X86_FEATURE_CLEAR_CPU_BUF	( 3*32+18) /* Clear CPU buffers using VERW */

arch/x86/kernel/cpu/centaur.c

+0 −3
Original line number Diff line number Diff line
@@ -102,9 +102,6 @@ static void early_init_centaur(struct cpuinfo_x86 *c) 
	    (c->x86 >= 7))

		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);



#ifdef CONFIG_X86_64

	set_cpu_cap(c, X86_FEATURE_SYSENTER32);

#endif

	if (c->x86_power & (1 << 8)) {

		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);

		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);

arch/x86/kernel/cpu/common.c

+8 −0
Original line number Diff line number Diff line
@@ -1068,6 +1068,9 @@ void get_cpu_cap(struct cpuinfo_x86 *c) 
	init_scattered_cpuid_features(c);

	init_speculation_control(c);



	if (IS_ENABLED(CONFIG_X86_64) || cpu_has(c, X86_FEATURE_SEP))

		set_cpu_cap(c, X86_FEATURE_SYSFAST32);



	/*

	 * Clear/Set all flags overridden by options, after probe.

	 * This needs to happen each time we re-probe, which may happen
@@ -1813,6 +1816,11 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) 
	 * that it can't be enabled in 32-bit mode.

	 */

	setup_clear_cpu_cap(X86_FEATURE_PCID);



	/*

	 * Never use SYSCALL on a 32-bit kernel

	 */

	setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);

#endif



	/*