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Peter Anvin" To: "H. Peter Anvin" , "Jason A. Donenfeld" , "Peter Zijlstra (Intel)" , "Theodore Ts'o" , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Xin Li , Andrew Cooper , Andy Lutomirski , Ard Biesheuvel , Borislav Petkov , Brian Gerst , Dave Hansen , Ingo Molnar , James Morse , Jarkko Sakkinen , Josh Poimboeuf , Kees Cook , Nam Cao , Oleg Nesterov , Perry Yuan , Thomas Gleixner , Thomas Huth , Uros Bizjak , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-sgx@vger.kernel.org, x86@kernel.org Subject: [PATCH v4 09/10] x86/cpufeature: replace X86_FEATURE_SYSENTER32 with X86_FEATURE_SYSFAST32 Date: Tue, 16 Dec 2025 13:26:03 -0800 Message-ID: <20251216212606.1325678-10-hpa@zytor.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216212606.1325678-1-hpa@zytor.com> References: <20251216212606.1325678-1-hpa@zytor.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 13C8818000E X-Rspamd-Server: rspam10 X-Stat-Signature: s69td1nfwwngeb67caqozzdu91djn7tx X-HE-Tag: 1765920418-167748 X-HE-Meta: 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 8oBuIUD4 qC/hifgOlbbYe1yDRQby0u+NRKtBcHE5UBuySvj/pItDYAasZYbFtuiHXU5UwuqfvRQMFgkJz0EBf2dTRp5PtRnIJTMtJzdaccQmivfwC+hYytKIkMxZzzZyq69IFMP11z6XisSrhMQcyj/EoNuJYd8AbuW3ZSunwNwdYZHwInxq9RRIvUL87A7kr50MEqL9IbdYKl/zymVgmV5N0mVw72CFgUub/Mi8sVppM/AIqe1TrOzTbYhllwv3RLNrCnIVwDmyoeKtKlLfD247LuhGD1Z0cng0+YNiK5k/voHoTMn14GrgzlBlNdbTjknHERoRH2aub/hKojnOt/o19Dbc6dDARKA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: H. Peter Anvin (Intel) --- arch/x86/Kconfig.cpufeatures | 8 +++++++ arch/x86/entry/vdso/vdso32/system_call.S | 8 ++----- arch/x86/include/asm/cpufeatures.h | 2 +- arch/x86/kernel/cpu/centaur.c | 3 --- arch/x86/kernel/cpu/common.c | 8 +++++++ arch/x86/kernel/cpu/intel.c | 4 +--- arch/x86/kernel/cpu/zhaoxin.c | 4 +--- arch/x86/kernel/fred.c | 2 +- arch/x86/xen/setup.c | 28 +++++++++++++++--------- arch/x86/xen/smp_pv.c | 5 ++--- arch/x86/xen/xen-ops.h | 1 - 11 files changed, 42 insertions(+), 31 deletions(-) diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures index 733d5aff2456..423ac795baa7 100644 --- a/arch/x86/Kconfig.cpufeatures +++ b/arch/x86/Kconfig.cpufeatures @@ -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 diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S index 2a15634bbe75..7b1c0f16e511 100644 --- a/arch/x86/entry/vdso/vdso32/system_call.S +++ b/arch/x86/entry/vdso/vdso32/system_call.S @@ -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, \ - SYSCALL_SEQUENCE, X86_FEATURE_SYSCALL32 -#else - ALTERNATIVE "", SYSENTER_SEQUENCE, X86_FEATURE_SEP -#endif + ALTERNATIVE_2 "", SYSENTER_SEQUENCE, X86_FEATURE_SYSFAST32, \ + SYSCALL_SEQUENCE, X86_FEATURE_SYSCALL32 /* Enter using int $0x80 */ int $0x80 diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index c3b53beb1300..63b0f9aa9b3e 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -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 */ diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c index a3b55db35c96..9833f837141c 100644 --- a/arch/x86/kernel/cpu/centaur.c +++ b/arch/x86/kernel/cpu/centaur.c @@ -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); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index e7ab22fce3b5..1c3261cae40c 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -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 /* diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 98ae4c37c93e..646ff33c4651 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -236,9 +236,7 @@ static void early_init_intel(struct cpuinfo_x86 *c) clear_cpu_cap(c, X86_FEATURE_PSE); } -#ifdef CONFIG_X86_64 - set_cpu_cap(c, X86_FEATURE_SYSENTER32); -#else +#ifndef CONFIG_X86_64 /* Netburst reports 64 bytes clflush size, but does IO in 128 bytes */ if (c->x86 == 15 && c->x86_cache_alignment == 64) c->x86_cache_alignment = 128; diff --git a/arch/x86/kernel/cpu/zhaoxin.c b/arch/x86/kernel/cpu/zhaoxin.c index 89b1c8a70fe8..031379b7d4fa 100644 --- a/arch/x86/kernel/cpu/zhaoxin.c +++ b/arch/x86/kernel/cpu/zhaoxin.c @@ -59,9 +59,7 @@ static void early_init_zhaoxin(struct cpuinfo_x86 *c) { if (c->x86 >= 0x6) 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); diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c index 816187da3a47..e736b19e18de 100644 --- a/arch/x86/kernel/fred.c +++ b/arch/x86/kernel/fred.c @@ -68,7 +68,7 @@ void cpu_init_fred_exceptions(void) idt_invalidate(); /* Use int $0x80 for 32-bit system calls in FRED mode */ - setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); + setup_clear_cpu_cap(X86_FEATURE_SYSFAST32); setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); } diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index 3823e52aef52..ac8021c3a997 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -990,13 +990,6 @@ static int register_callback(unsigned type, const void *func) return HYPERVISOR_callback_op(CALLBACKOP_register, &callback); } -void xen_enable_sysenter(void) -{ - if (cpu_feature_enabled(X86_FEATURE_SYSENTER32) && - register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat)) - setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); -} - void xen_enable_syscall(void) { int ret; @@ -1008,11 +1001,27 @@ void xen_enable_syscall(void) mechanism for syscalls. */ } - if (cpu_feature_enabled(X86_FEATURE_SYSCALL32) && - register_callback(CALLBACKTYPE_syscall32, xen_entry_SYSCALL_compat)) + if (!cpu_feature_enabled(X86_FEATURE_SYSFAST32)) + return; + + if (cpu_feature_enabled(X86_FEATURE_SYSCALL32)) { + /* Use SYSCALL32 */ + ret = register_callback(CALLBACKTYPE_syscall32, + xen_entry_SYSCALL_compat); + + } else { + /* Use SYSENTER32 */ + ret = register_callback(CALLBACKTYPE_sysenter, + xen_entry_SYSENTER_compat); + } + + if (ret) { setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); + setup_clear_cpu_cap(X86_FEATURE_SYSFAST32); + } } + static void __init xen_pvmmu_arch_setup(void) { HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_writable_pagetables); @@ -1022,7 +1031,6 @@ static void __init xen_pvmmu_arch_setup(void) register_callback(CALLBACKTYPE_failsafe, xen_failsafe_callback)) BUG(); - xen_enable_sysenter(); xen_enable_syscall(); } diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 9bb8ff8bff30..c40f326f0c3a 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -65,10 +65,9 @@ static void cpu_bringup(void) touch_softlockup_watchdog(); /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */ - if (!xen_feature(XENFEAT_supervisor_mode_kernel)) { - xen_enable_sysenter(); + if (!xen_feature(XENFEAT_supervisor_mode_kernel)) xen_enable_syscall(); - } + cpu = smp_processor_id(); identify_secondary_cpu(cpu); set_cpu_sibling_map(cpu); diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 090349baec09..f6c331b20fad 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -60,7 +60,6 @@ phys_addr_t __init xen_find_free_area(phys_addr_t size); char * __init xen_memory_setup(void); void __init xen_arch_setup(void); void xen_banner(void); -void xen_enable_sysenter(void); void xen_enable_syscall(void); void xen_vcpu_restore(void); -- 2.52.0