Hi Brendan, On Fri, Jan 10, 2025 at 06:40:28PM +0000, Brendan Jackman wrote: > Currently a nop config. Keeping as a separate commit for easy review of > the boring bits. Later commits will use and enable this new config. > > This config is only added for non-UML x86_64 as other architectures do > not yet have pending implementations. It also has somewhat artificial > dependencies on !PARAVIRT and !KASAN which are explained in the Kconfig > file. > > Co-developed-by: Junaid Shahid <junaids@xxxxxxxxxx> > Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx> > Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx> > --- > arch/alpha/include/asm/Kbuild | 1 + > arch/arc/include/asm/Kbuild | 1 + > arch/arm/include/asm/Kbuild | 1 + > arch/arm64/include/asm/Kbuild | 1 + > arch/csky/include/asm/Kbuild | 1 + > arch/hexagon/include/asm/Kbuild | 1 + > arch/loongarch/include/asm/Kbuild | 3 +++ > arch/m68k/include/asm/Kbuild | 1 + > arch/microblaze/include/asm/Kbuild | 1 + > arch/mips/include/asm/Kbuild | 1 + > arch/nios2/include/asm/Kbuild | 1 + > arch/openrisc/include/asm/Kbuild | 1 + > arch/parisc/include/asm/Kbuild | 1 + > arch/powerpc/include/asm/Kbuild | 1 + > arch/riscv/include/asm/Kbuild | 1 + > arch/s390/include/asm/Kbuild | 1 + > arch/sh/include/asm/Kbuild | 1 + > arch/sparc/include/asm/Kbuild | 1 + > arch/um/include/asm/Kbuild | 2 +- > arch/x86/Kconfig | 14 ++++++++++++++ > arch/xtensa/include/asm/Kbuild | 1 + > include/asm-generic/asi.h | 5 +++++ > 22 files changed, 41 insertions(+), 1 deletion(-) I don't think this all is needed. You can put asi.h with stubs used outside of arch/x86 in include/linux and save you the hassle of updating every architecture. > diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild > index 43b0ae4c2c2112d4d4d3cb3c60e787b175172dea..cb9062c9be17fe276cc92d2ac99d8b165f6297bf 100644 > --- a/arch/sparc/include/asm/Kbuild > +++ b/arch/sparc/include/asm/Kbuild > @@ -4,3 +4,4 @@ generated-y += syscall_table_64.h > generic-y += agp.h > generic-y += kvm_para.h > generic-y += mcs_spinlock.h > +generic-y += asi.h sparc already has include/asm/asi.h, this will break the build > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 7b9a7e8f39acc8e9aeb7d4213e87d71047865f5c..5a50582eb210e9d1309856a737d32b76fa1bfc85 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -2519,6 +2519,20 @@ config MITIGATION_PAGE_TABLE_ISOLATION > > See Documentation/arch/x86/pti.rst for more details. > > +config MITIGATION_ADDRESS_SPACE_ISOLATION > + bool "Allow code to run with a reduced kernel address space" > + default n > + depends on X86_64 && !PARAVIRT && !UML > + help > + This feature provides the ability to run some kernel code > + with a reduced kernel address space. This can be used to > + mitigate some speculative execution attacks. > + > + The !PARAVIRT dependency is only because of lack of testing; in theory > + the code is written to work under paravirtualization. In practice > + there are likely to be unhandled cases, in particular concerning TLB > + flushes. > + If you expect other architectures might implement ASI the config would better fit into init/Kconfig or mm/Kconfig and in arch/x86/Kconfig will define ARCH_HAS_MITIGATION_ADDRESS_SPACE_ISOLATION. > config MITIGATION_RETPOLINE > bool "Avoid speculative indirect branches in kernel" > select OBJTOOL if HAVE_OBJTOOL > diff --git a/arch/xtensa/include/asm/Kbuild b/arch/xtensa/include/asm/Kbuild > index fa07c686cbcc2153776a478ac4093846f01eddab..07cea6902f98053be244d026ed594fe7246755a6 100644 > --- a/arch/xtensa/include/asm/Kbuild > +++ b/arch/xtensa/include/asm/Kbuild > @@ -8,3 +8,4 @@ generic-y += parport.h > generic-y += qrwlock.h > generic-y += qspinlock.h > generic-y += user.h > +generic-y += asi.h > diff --git a/include/asm-generic/asi.h b/include/asm-generic/asi.h > new file mode 100644 > index 0000000000000000000000000000000000000000..c4d9a5ff860a96428422a15000c622aeecc2d664 > --- /dev/null > +++ b/include/asm-generic/asi.h > @@ -0,0 +1,5 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_GENERIC_ASI_H > +#define __ASM_GENERIC_ASI_H > + > +#endif IMHO it should be include/linux/asi.h, with something like #infdef __LINUX_ASI_H #define __LINUX_ASI_H #ifdef CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION #include <asm/asi.h> #else /* CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION */ /* stubs for functions used outside arch/ */ #endif /* CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION */ #endif /* __LINUX_ASI_H */ -- Sincerely yours, Mike.
