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Message-ID: <Z8K2B3WJoICVbDj3@kernel.org> Date: Sat, 1 Mar 2025 09:23:51 +0200 From: Mike Rapoport <rppt@...nel.org> To: Brendan Jackman <jackmanb@...gle.com> Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Richard Henderson <richard.henderson@...aro.org>, Matt Turner <mattst88@...il.com>, Vineet Gupta <vgupta@...nel.org>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>, Brian Cain <bcain@...cinc.com>, Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, Geert Uytterhoeven <geert@...ux-m68k.org>, Michal Simek <monstr@...str.eu>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Dinh Nguyen <dinguyen@...nel.org>, Jonas Bonn <jonas@...thpole.se>, Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>, Stafford Horne <shorne@...il.com>, "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, Helge Deller <deller@....de>, Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, Naveen N Rao <naveen@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.com>, Yoshinori Sato <ysato@...rs.sourceforge.jp>, Rich Felker <dalias@...c.org>, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, "David S. Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>, Richard Weinberger <richard@....at>, Anton Ivanov <anton.ivanov@...bridgegreys.com>, Johannes Berg <johannes@...solutions.net>, Chris Zankel <chris@...kel.net>, Max Filippov <jcmvbkbc@...il.com>, Arnd Bergmann <arnd@...db.de>, Andrew Morton <akpm@...ux-foundation.org>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>, Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>, Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Ard Biesheuvel <ardb@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, x86@...nel.org, linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org, loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org, linux-openrisc@...r.kernel.org, linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org, linux-sh@...r.kernel.org, sparclinux@...r.kernel.org, linux-um@...ts.infradead.org, linux-arch@...r.kernel.org, linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, kvm@...r.kernel.org, linux-efi@...r.kernel.org, Junaid Shahid <junaids@...gle.com> Subject: Re: [PATCH RFC v2 02/29] x86: Create CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION 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@...gle.com> > Signed-off-by: Junaid Shahid <junaids@...gle.com> > Signed-off-by: Brendan Jackman <jackmanb@...gle.com> > --- > 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.
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