From 50cc02e599ef1e049473358604dc07d32b751e2c Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 27 Dec 2019 17:36:12 +0100 Subject: x86/context-tracking: Remove exception_enter/exit() from KVM_PV_REASON_PAGE_NOT_PRESENT async page fault MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is a leftover. Page faults, just like most other exceptions, are protected inside user_exit() / user_enter() calls in x86 entry code when we fault from userspace. So this pair of calls is now superfluous. Signed-off-by: Frederic Weisbecker Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Jim Mattson Cc: Joerg Roedel Cc: Linus Torvalds Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Radim Krčmář Cc: Sean Christopherson Cc: Thomas Gleixner Cc: Vitaly Kuznetsov Cc: Wanpeng Li Link: https://lkml.kernel.org/r/20191227163612.10039-3-frederic@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/kvm.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 32ef1ee733b7..81045aabb6f4 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -245,17 +245,13 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason); dotraplinkage void do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address) { - enum ctx_state prev_state; - switch (kvm_read_and_reset_pf_reason()) { default: do_page_fault(regs, error_code, address); break; case KVM_PV_REASON_PAGE_NOT_PRESENT: /* page is swapped out by the host. */ - prev_state = exception_enter(); kvm_async_pf_task_wait((u32)address, !user_mode(regs)); - exception_exit(prev_state); break; case KVM_PV_REASON_PAGE_READY: rcu_irq_enter(); -- cgit v1.2.3-59-g8ed1b From 2b10906f2d25515bba58070b8183babc89063597 Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Thu, 19 Dec 2019 06:58:12 -0500 Subject: x86: Remove force_iret() force_iret() was originally intended to prevent the return to user mode with the SYSRET or SYSEXIT instructions, in cases where the register state could have been changed to be incompatible with those instructions. The entry code has been significantly reworked since then, and register state is validated before SYSRET or SYSEXIT are used. force_iret() no longer serves its original purpose and can be eliminated. Signed-off-by: Brian Gerst Signed-off-by: Borislav Petkov Acked-by: Oleg Nesterov Link: https://lkml.kernel.org/r/20191219115812.102620-1-brgerst@gmail.com --- arch/x86/ia32/ia32_signal.c | 2 -- arch/x86/include/asm/ptrace.h | 16 ---------------- arch/x86/include/asm/thread_info.h | 9 --------- arch/x86/kernel/process_32.c | 1 - arch/x86/kernel/process_64.c | 1 - arch/x86/kernel/signal.c | 2 -- arch/x86/kernel/vm86_32.c | 1 - 7 files changed, 32 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c index 30416d7f19d4..a3aefe9b9401 100644 --- a/arch/x86/ia32/ia32_signal.c +++ b/arch/x86/ia32/ia32_signal.c @@ -114,8 +114,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, err |= fpu__restore_sig(buf, 1); - force_iret(); - return err; } diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 5057a8ed100b..78897a8da01f 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -339,22 +339,6 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs, #define ARCH_HAS_USER_SINGLE_STEP_REPORT -/* - * When hitting ptrace_stop(), we cannot return using SYSRET because - * that does not restore the full CPU state, only a minimal set. The - * ptracer can change arbitrary register values, which is usually okay - * because the usual ptrace stops run off the signal delivery path which - * forces IRET; however, ptrace_event() stops happen in arbitrary places - * in the kernel and don't force IRET path. - * - * So force IRET path after a ptrace stop. - */ -#define arch_ptrace_stop_needed(code, info) \ -({ \ - force_iret(); \ - false; \ -}) - struct user_desc; extern int do_get_thread_area(struct task_struct *p, int idx, struct user_desc __user *info); diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index d779366ce3f8..cf4327986e98 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -239,15 +239,6 @@ static inline int arch_within_stack_frames(const void * const stack, current_thread_info()->status & TS_COMPAT) #endif -/* - * Force syscall return via IRET by making it look as if there was - * some work pending. IRET is our most capable (but slowest) syscall - * return path, which is able to restore modified SS, CS and certain - * EFLAGS values that other (fast) syscall return instructions - * are not able to restore properly. - */ -#define force_iret() set_thread_flag(TIF_NOTIFY_RESUME) - extern void arch_task_cache_init(void); extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); extern void arch_release_task_struct(struct task_struct *tsk); diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 323499f48858..5052ced43373 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -124,7 +124,6 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) regs->ip = new_ip; regs->sp = new_sp; regs->flags = X86_EFLAGS_IF; - force_iret(); } EXPORT_SYMBOL_GPL(start_thread); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 506d66830d4d..ffd497804dbc 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -394,7 +394,6 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, regs->cs = _cs; regs->ss = _ss; regs->flags = X86_EFLAGS_IF; - force_iret(); } void diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 8eb7193e158d..8a29573851a3 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -151,8 +151,6 @@ static int restore_sigcontext(struct pt_regs *regs, err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32)); - force_iret(); - return err; } diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c index a76c12b38e92..91d55454e702 100644 --- a/arch/x86/kernel/vm86_32.c +++ b/arch/x86/kernel/vm86_32.c @@ -381,7 +381,6 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus) mark_screen_rdonly(tsk->mm); memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs)); - force_iret(); return regs->ax; } -- cgit v1.2.3-59-g8ed1b