Commit-ID: 7d79adb87fa79e4a4c59424fd5b5a922861fc5f6 Gitweb: https://git.kernel.org/tip/7d79adb87fa79e4a4c59424fd5b5a922861fc5f6 Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> AuthorDate: Thu, 29 Nov 2018 16:02:10 +0100 Committer: Borislav Petkov <bp@xxxxxxx> CommitDate: Mon, 3 Dec 2018 19:37:27 +0100 x86/fpu: Don't export __kernel_fpu_{begin,end}() There is one user of __kernel_fpu_begin() and before invoking it, it invokes preempt_disable(). So it could invoke kernel_fpu_begin() right away. The 32bit version of arch_efi_call_virt_setup() and arch_efi_call_virt_teardown() does this already. The comment above *kernel_fpu*() claims that before invoking __kernel_fpu_begin() preemption should be disabled and that KVM is a good example of doing it. Well, KVM doesn't do that since commit f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") so it is not an example anymore. With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can be made static and not exported anymore. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Rik van Riel <riel@xxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Nicolai Stange <nstange@xxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: kvm ML <kvm@xxxxxxxxxxxxxxx> Cc: linux-efi <linux-efi@xxxxxxxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@xxxxxxxxxxxxx --- arch/x86/include/asm/efi.h | 6 ++---- arch/x86/include/asm/fpu/api.h | 16 ++++++---------- arch/x86/kernel/fpu/core.c | 6 ++---- 3 files changed, 10 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index eea40d52ca78..45864898f7e5 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -82,8 +82,7 @@ struct efi_scratch { #define arch_efi_call_virt_setup() \ ({ \ efi_sync_low_kernel_mappings(); \ - preempt_disable(); \ - __kernel_fpu_begin(); \ + kernel_fpu_begin(); \ firmware_restrict_branch_speculation_start(); \ \ if (!efi_enabled(EFI_OLD_MEMMAP)) \ @@ -99,8 +98,7 @@ struct efi_scratch { efi_switch_mm(efi_scratch.prev_mm); \ \ firmware_restrict_branch_speculation_end(); \ - __kernel_fpu_end(); \ - preempt_enable(); \ + kernel_fpu_end(); \ }) extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size, diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index a9caac9d4a72..e368d8d94ca6 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -12,17 +12,13 @@ #define _ASM_X86_FPU_API_H /* - * Careful: __kernel_fpu_begin/end() must be called with preempt disabled - * and they don't touch the preempt state on their own. - * If you enable preemption after __kernel_fpu_begin(), preempt notifier - * should call the __kernel_fpu_end() to prevent the kernel/user FPU - * state from getting corrupted. KVM for example uses this model. - * - * All other cases use kernel_fpu_begin/end() which disable preemption - * during kernel FPU usage. + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It + * disables preemption so be careful if you intend to use it for long periods + * of time. + * If you intend to use the FPU in softirq you need to check first with + * irq_fpu_usable() if it is possible. + * Using the FPU in hardirq is not allowed. */ -extern void __kernel_fpu_begin(void); -extern void __kernel_fpu_end(void); extern void kernel_fpu_begin(void); extern void kernel_fpu_end(void); extern bool irq_fpu_usable(void); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 2ea85b32421a..2e5003fef51a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -93,7 +93,7 @@ bool irq_fpu_usable(void) } EXPORT_SYMBOL(irq_fpu_usable); -void __kernel_fpu_begin(void) +static void __kernel_fpu_begin(void) { struct fpu *fpu = ¤t->thread.fpu; @@ -111,9 +111,8 @@ void __kernel_fpu_begin(void) __cpu_invalidate_fpregs_state(); } } -EXPORT_SYMBOL(__kernel_fpu_begin); -void __kernel_fpu_end(void) +static void __kernel_fpu_end(void) { struct fpu *fpu = ¤t->thread.fpu; @@ -122,7 +121,6 @@ void __kernel_fpu_end(void) kernel_fpu_enable(); } -EXPORT_SYMBOL(__kernel_fpu_end); void kernel_fpu_begin(void) {
