* [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() [not found] <20190430113608.616903219@linuxfoundation.org> @ 2019-04-30 11:38 ` Greg Kroah-Hartman 2019-04-30 11:38 ` Greg Kroah-Hartman 2019-05-01 11:59 ` Lukas Wunner 0 siblings, 2 replies; 4+ messages in thread From: Greg Kroah-Hartman @ 2019-04-30 11:38 UTC (permalink / raw) To: linux-kernel Cc: Greg Kroah-Hartman, stable, Sebastian Andrzej Siewior, Borislav Petkov, Rik van Riel, H. Peter Anvin, Jason A. Donenfeld, Andy Lutomirski, Ard Biesheuvel, Dave Hansen, Ingo Molnar, Nicolai Stange, Paolo Bonzini, Radim Krčmář, Thomas Gleixner, kvm ML, linux-efi, x86-ml From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> commit 12209993e98c5fa1855c467f22a24e3d5b8be205 upstream. 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@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Rik van Riel <riel@surriel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Nicolai Stange <nstange@suse.de> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kvm ML <kvm@vger.kernel.org> Cc: linux-efi <linux-efi@vger.kernel.org> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/include/asm/efi.h | 6 ++---- arch/x86/include/asm/fpu/api.h | 15 +++++---------- arch/x86/kernel/fpu/core.c | 6 ++---- 3 files changed, 9 insertions(+), 18 deletions(-) --- 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, --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -12,17 +12,12 @@ #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. */ -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); --- 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) { ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() 2019-04-30 11:38 ` [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() Greg Kroah-Hartman @ 2019-04-30 11:38 ` Greg Kroah-Hartman 2019-05-01 11:59 ` Lukas Wunner 1 sibling, 0 replies; 4+ messages in thread From: Greg Kroah-Hartman @ 2019-04-30 11:38 UTC (permalink / raw) To: linux-kernel Cc: Greg Kroah-Hartman, stable, Sebastian Andrzej Siewior, Borislav Petkov, Rik van Riel, H. Peter Anvin, Jason A. Donenfeld, Andy Lutomirski, Ard Biesheuvel, Dave Hansen, Ingo Molnar, Nicolai Stange, Paolo Bonzini, Radim Krčmář, Thomas Gleixner, kvm ML, linux-efi, x86-ml From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> commit 12209993e98c5fa1855c467f22a24e3d5b8be205 upstream. 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@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Rik van Riel <riel@surriel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Nicolai Stange <nstange@suse.de> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kvm ML <kvm@vger.kernel.org> Cc: linux-efi <linux-efi@vger.kernel.org> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/include/asm/efi.h | 6 ++---- arch/x86/include/asm/fpu/api.h | 15 +++++---------- arch/x86/kernel/fpu/core.c | 6 ++---- 3 files changed, 9 insertions(+), 18 deletions(-) --- 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, --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -12,17 +12,12 @@ #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. */ -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); --- 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) { ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() 2019-04-30 11:38 ` [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() Greg Kroah-Hartman 2019-04-30 11:38 ` Greg Kroah-Hartman @ 2019-05-01 11:59 ` Lukas Wunner 2019-05-01 11:59 ` Lukas Wunner 1 sibling, 1 reply; 4+ messages in thread From: Lukas Wunner @ 2019-05-01 11:59 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: linux-kernel, stable, Sebastian Andrzej Siewior, Borislav Petkov, Rik van Riel, H. Peter Anvin, Jason A. Donenfeld, Andy Lutomirski, Ard Biesheuvel, Dave Hansen, Ingo Molnar, Nicolai Stange, Paolo Bonzini, Radim Kr??má??, Thomas Gleixner, kvm ML, linux-efi, x86-ml On Tue, Apr 30, 2019 at 01:38:52PM +0200, Greg Kroah-Hartman wrote: > commit 12209993e98c5fa1855c467f22a24e3d5b8be205 upstream. > > 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. This is just a cleanup and therefore doesn't seem to satisfy the rules for stable patches per Documentation/process/stable-kernel-rules.rst ("It must fix a real bug that bothers people / fix a problem that causes a build error"). Why is it being queued up for stable and why are the rules disregarded here? Thanks, Lukas ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() 2019-05-01 11:59 ` Lukas Wunner @ 2019-05-01 11:59 ` Lukas Wunner 0 siblings, 0 replies; 4+ messages in thread From: Lukas Wunner @ 2019-05-01 11:59 UTC (permalink / raw) To: Greg Kroah-Hartman Cc: linux-kernel, stable, Sebastian Andrzej Siewior, Borislav Petkov, Rik van Riel, H. Peter Anvin, Jason A. Donenfeld, Andy Lutomirski, Ard Biesheuvel, Dave Hansen, Ingo Molnar, Nicolai Stange, Paolo Bonzini, Radim Kr??má??, Thomas Gleixner, kvm ML, linux-efi, x86-ml On Tue, Apr 30, 2019 at 01:38:52PM +0200, Greg Kroah-Hartman wrote: > commit 12209993e98c5fa1855c467f22a24e3d5b8be205 upstream. > > 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. This is just a cleanup and therefore doesn't seem to satisfy the rules for stable patches per Documentation/process/stable-kernel-rules.rst ("It must fix a real bug that bothers people / fix a problem that causes a build error"). Why is it being queued up for stable and why are the rules disregarded here? Thanks, Lukas ^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-04-30 11:38 ` [PATCH 4.19 083/100] x86/fpu: Dont export __kernel_fpu_{begin,end}() Greg Kroah-Hartman
2019-04-30 11:38 ` Greg Kroah-Hartman
2019-05-01 11:59 ` Lukas Wunner
2019-05-01 11:59 ` Lukas Wunner
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