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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jiri Kosina <jkosina@suse.cz>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Casey Schaufler <casey.schaufler@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Jon Masters <jcm@redhat.com>, Waiman Long <longman9394@gmail.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Dave Stewart <david.c.stewart@intel.com>,
	Kees Cook <keescook@chromium.org>
Subject: [patch V2 21/28] x86/speculation: Prepare for conditional IBPB in switch_mm()
Date: Sun, 25 Nov 2018 19:33:49 +0100
Message-ID: <20181125185005.466447057@linutronix.de> (raw)
In-Reply-To: <20181125183328.318175777@linutronix.de>


[-- Attachment #0: x86-speculation--Prepare-for-conditional-IBPB-in-switch_mm--.patch --]
[-- Type: text/plain, Size: 10124 bytes --]

The IBPB speculation barrier is issued from switch_mm() when the kernel
switches to a user space task with a different mm than the user space task
which ran last on the same CPU.

An additional optimization is to avoid IBPB when the incoming task can be
ptraced by the outgoing task. This optimization only works when switching
directly between two user space tasks. When switching from a kernel task to
a user space task the optimization fails because the previous task cannot
be accessed anymore. So for quite some scenarios the optimization is just
adding overhead.

The upcoming conditional IBPB support will issue IBPB only for user space
tasks which have the TIF_SPEC_IB bit set. This requires to handle the
following cases:

  1) Switch from a user space task (potential attacker) which has
     TIF_SPEC_IB set to a user space task (potential victim) which has
     TIF_SPEC_IB not set.

  2) Switch from a user space task (potential attacker) which has
     TIF_SPEC_IB not set to a user space task (potential victim) which has
     TIF_SPEC_IB set.

This needs to be optimized for the case where the IBPB can be avoided when
only kernel threads ran in between user space tasks which belong to the
same process.

The current check whether two tasks belong to the same context is using the
tasks context id. While correct, it's simpler to use the mm pointer because
it allows to mangle the TIF_SPEC_IB bit into it. The context id based
mechanism requires extra storage, which creates worse code.

When a task is scheduled out its TIF_SPEC_IB bit is mangled as bit 0 into
the per CPU storage which is used to track the last user space mm which was
running on a CPU. This bit can be used together with the TIF_SPEC_IB bit of
the incoming task to make the decision whether IBPB needs to be issued or
not to cover the two cases above.

As conditional IBPB is going to be the default, remove the dubious ptrace
check for the IBPB always case and simply issue IBPB always when the
process changes.

Move the storage to a different place in the struct as the original one
created a hole.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/nospec-branch.h |    2 
 arch/x86/include/asm/tlbflush.h      |    8 +-
 arch/x86/kernel/cpu/bugs.c           |   29 +++++++--
 arch/x86/mm/tlb.c                    |  109 +++++++++++++++++++++++++----------
 4 files changed, 110 insertions(+), 38 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -312,6 +312,8 @@ do {									\
 } while (0)
 
 DECLARE_STATIC_KEY_FALSE(switch_to_cond_stibp);
+DECLARE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
+DECLARE_STATIC_KEY_FALSE(switch_mm_always_ibpb);
 
 #endif /* __ASSEMBLY__ */
 
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -169,10 +169,14 @@ struct tlb_state {
 
 #define LOADED_MM_SWITCHING ((struct mm_struct *)1)
 
+	/* Last user mm for optimizing IBPB */
+	union {
+		struct mm_struct	*last_user_mm;
+		unsigned long		last_user_mm_ibpb;
+	};
+
 	u16 loaded_mm_asid;
 	u16 next_asid;
-	/* last user mm's ctx id */
-	u64 last_ctx_id;
 
 	/*
 	 * We can be in one of several states:
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -56,6 +56,10 @@ u64 __ro_after_init x86_amd_ls_cfg_ssbd_
 
 /* Control conditional STIPB in switch_to() */
 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
+/* Control conditional IBPB in switch_mm() */
+DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
+/* Control unconditional IBPB in switch_mm() */
+DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb);
 
 void __init check_bugs(void)
 {
@@ -331,7 +335,17 @@ spectre_v2_user_select_mitigation(enum s
 	/* Initialize Indirect Branch Prediction Barrier */
 	if (boot_cpu_has(X86_FEATURE_IBPB)) {
 		setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
-		pr_info("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n");
+
+		switch (mode) {
+		case SPECTRE_V2_USER_STRICT:
+			static_branch_enable(&switch_mm_always_ibpb);
+			break;
+		default:
+			break;
+		}
+
+		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
+			mode == SPECTRE_V2_USER_STRICT ? "always-on" : "conditional");
 	}
 
 	/* If enhanced IBRS is enabled no STIPB required */
@@ -955,10 +969,15 @@ static char *stibp_state(void)
 
 static char *ibpb_state(void)
 {
-	if (boot_cpu_has(X86_FEATURE_USE_IBPB))
-		return ", IBPB";
-	else
-		return "";
+	if (boot_cpu_has(X86_FEATURE_IBPB)) {
+		switch (spectre_v2_user) {
+		case SPECTRE_V2_USER_NONE:
+			return ", IBPB: disabled";
+		case SPECTRE_V2_USER_STRICT:
+			return ", IBPB: always-on";
+		}
+	}
+	return "";
 }
 
 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -7,7 +7,6 @@
 #include <linux/export.h>
 #include <linux/cpu.h>
 #include <linux/debugfs.h>
-#include <linux/ptrace.h>
 
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
@@ -31,6 +30,12 @@
  */
 
 /*
+ * Use bit 0 to mangle the TIF_SPEC_IB state into the mm pointer which is
+ * stored in cpu_tlb_state.last_user_mm_ibpb.
+ */
+#define LAST_USER_MM_IBPB	0x1UL
+
+/*
  * We get here when we do something requiring a TLB invalidation
  * but could not go invalidate all of the contexts.  We do the
  * necessary invalidation by clearing out the 'ctx_id' which
@@ -181,17 +186,77 @@ static void sync_current_stack_to_mm(str
 	}
 }
 
-static bool ibpb_needed(struct task_struct *tsk, u64 last_ctx_id)
+static inline unsigned long mm_mangle_tif_spec_ib(struct task_struct *next)
 {
-	/*
-	 * Check if the current (previous) task has access to the memory
-	 * of the @tsk (next) task. If access is denied, make sure to
-	 * issue a IBPB to stop user->user Spectre-v2 attacks.
-	 *
-	 * Note: __ptrace_may_access() returns 0 or -ERRNO.
-	 */
-	return (tsk && tsk->mm && tsk->mm->context.ctx_id != last_ctx_id &&
-		ptrace_may_access_sched(tsk, PTRACE_MODE_SPEC_IBPB));
+	unsigned long next_tif = task_thread_info(next)->flags;
+	unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USR_MM_IBPB;
+
+	return (unsigned long)next->mm | ibpb;
+}
+
+static void cond_ibpb(struct task_struct *next)
+{
+	if (!next || !next->mm)
+		return;
+
+	if (static_branch_likely(&switch_mm_cond_ibpb)) {
+		unsigned long prev_mm, next_mm;
+
+		/*
+		 * This is a bit more complex than the always mode because
+		 * it has to handle two cases:
+		 *
+		 * 1) Switch from a user space task (potential attacker)
+		 *    which has TIF_SPEC_IB set to a user space task
+		 *    (potential victim) which has TIF_SPEC_IB not set.
+		 *
+		 * 2) Switch from a user space task (potential attacker)
+		 *    which has TIF_SPEC_IB not set to a user space task
+		 *    (potential victim) which has TIF_SPEC_IB set.
+		 *
+		 * This could be done by unconditionally issuing IBPB when
+		 * a task which has TIF_SPEC_IB set is either scheduled in
+		 * or out. Though that results in two flushes when:
+		 *
+		 * - the same user space task is scheduled out and later
+		 *   scheduled in again and only a kernel thread ran in
+		 *   between.
+		 *
+		 * - a user space task belonging to the same process is
+		 *   scheduled in after a kernel thread ran in between
+		 *
+		 * - a user space task belonging to the same process is
+		 *   scheduled in immediately.
+		 *
+		 * Optimize this with reasonably small overhead for the
+		 * above cases. Mangle the TIF_SPEC_IB bit into the mm
+		 * pointer of the incoming task which is stored in
+		 * cpu_tlbstate.last_user_mm_ibpb for comparison.
+		 */
+		next_mm = mm_mangle_tif_spec_ib(next);
+		prev_mm = this_cpu_read(cpu_tlbstate.last_user_mm_ibpb);
+
+		/*
+		 * Issue IBPB only if the mm's are different and one or
+		 * both have the IBPB bit set.
+		 */
+		if (next_mm != prev_mm && (next_mm | prev_mm) & LAST_USR_MM_IBPB)
+			indirect_branch_prediction_barrier();
+
+		this_cpu_write(cpu_tlbstate.last_user_mm_ibpb, next_mm);
+	}
+
+	if (static_branch_unlikely(&switch_mm_always_ibpb)) {
+		/*
+		 * Only flush when switching to a user space task with a
+		 * different context than the user space task which ran
+		 * last on this CPU.
+		 */
+		if (this_cpu_read(cpu_tlbstate.last_user_mm) != next->mm) {
+			indirect_branch_prediction_barrier();
+			this_cpu_write(cpu_tlbstate.last_user_mm, next->mm);
+		}
+	}
 }
 
 void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
@@ -292,22 +357,12 @@ void switch_mm_irqs_off(struct mm_struct
 		new_asid = prev_asid;
 		need_flush = true;
 	} else {
-		u64 last_ctx_id = this_cpu_read(cpu_tlbstate.last_ctx_id);
-
 		/*
 		 * Avoid user/user BTB poisoning by flushing the branch
 		 * predictor when switching between processes. This stops
 		 * one process from doing Spectre-v2 attacks on another.
-		 *
-		 * As an optimization, flush indirect branches only when
-		 * switching into a processes that can't be ptrace by the
-		 * current one (as in such case, attacker has much more
-		 * convenient way how to tamper with the next process than
-		 * branch buffer poisoning).
 		 */
-		if (static_cpu_has(X86_FEATURE_USE_IBPB) &&
-				ibpb_needed(tsk, last_ctx_id))
-			indirect_branch_prediction_barrier();
+		cond_ibpb(tsk);
 
 		if (IS_ENABLED(CONFIG_VMAP_STACK)) {
 			/*
@@ -365,14 +420,6 @@ void switch_mm_irqs_off(struct mm_struct
 		trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, 0);
 	}
 
-	/*
-	 * Record last user mm's context id, so we can avoid
-	 * flushing branch buffer with IBPB if we switch back
-	 * to the same user.
-	 */
-	if (next != &init_mm)
-		this_cpu_write(cpu_tlbstate.last_ctx_id, next->context.ctx_id);
-
 	/* Make sure we write CR3 before loaded_mm. */
 	barrier();
 
@@ -441,7 +488,7 @@ void initialize_tlbstate_and_flush(void)
 	write_cr3(build_cr3(mm->pgd, 0));
 
 	/* Reinitialize tlbstate. */
-	this_cpu_write(cpu_tlbstate.last_ctx_id, mm->context.ctx_id);
+	this_cpu_write(cpu_tlbstate.last_user_mm_ibpb, LAST_USR_MM_IBPB);
 	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);
 	this_cpu_write(cpu_tlbstate.next_asid, 1);
 	this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);



  parent reply index

Thread overview: 112+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-25 18:33 [patch V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead Thomas Gleixner
2018-11-25 18:33 ` [patch V2 01/28] x86/speculation: Update the TIF_SSBD comment Thomas Gleixner
2018-11-28 14:20   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:27   ` [patch V2 01/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 02/28] x86/speculation: Clean up spectre_v2_parse_cmdline() Thomas Gleixner
2018-11-28 14:20   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:28   ` [patch V2 02/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 03/28] x86/speculation: Remove unnecessary ret variable in cpu_show_common() Thomas Gleixner
2018-11-28 14:21   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:28   ` [patch V2 03/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 04/28] x86/speculation: Reorganize cpu_show_common() Thomas Gleixner
2018-11-26 15:08   ` Borislav Petkov
2018-11-28 14:22   ` [tip:x86/pti] x86/speculation: Move STIPB/IBPB string conditionals out of cpu_show_common() tip-bot for Tim Chen
2018-11-29 14:29   ` [patch V2 04/28] x86/speculation: Reorganize cpu_show_common() Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 05/28] x86/speculation: Disable STIBP when enhanced IBRS is in use Thomas Gleixner
2018-11-28 14:22   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:35   ` [patch V2 05/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 06/28] x86/speculation: Rename SSBD update functions Thomas Gleixner
2018-11-26 15:24   ` Borislav Petkov
2018-11-28 14:23   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:37   ` [patch V2 06/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 07/28] x86/speculation: Reorganize speculation control MSRs update Thomas Gleixner
2018-11-26 15:47   ` Borislav Petkov
2018-11-28 14:23   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-29 14:41   ` [patch V2 07/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 08/28] sched/smt: Make sched_smt_present track topology Thomas Gleixner
2018-11-28 14:24   ` [tip:x86/pti] " tip-bot for Peter Zijlstra (Intel)
2018-11-29 14:42   ` [patch V2 08/28] " Konrad Rzeszutek Wilk
2018-11-29 14:50     ` Konrad Rzeszutek Wilk
2018-11-29 15:48       ` Peter Zijlstra
2018-11-25 18:33 ` [patch V2 09/28] x86/Kconfig: Select SCHED_SMT if SMP enabled Thomas Gleixner
2018-11-28 14:24   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:44   ` [patch V2 09/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 10/28] sched/smt: Expose sched_smt_present static key Thomas Gleixner
2018-11-28 14:25   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-29 14:44   ` [patch V2 10/28] " Konrad Rzeszutek Wilk
2018-11-25 18:33 ` [patch V2 11/28] x86/speculation: Rework SMT state change Thomas Gleixner
2018-11-28 14:26   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 12/28] x86/l1tf: Show actual SMT state Thomas Gleixner
2018-11-28 14:26   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 13/28] x86/speculation: Reorder the spec_v2 code Thomas Gleixner
2018-11-26 22:21   ` Borislav Petkov
2018-11-28 14:27   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 14/28] x86/speculation: Mark string arrays const correctly Thomas Gleixner
2018-11-28 14:27   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 15/28] x86/speculataion: Mark command line parser data __initdata Thomas Gleixner
2018-11-28 14:28   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 16/28] x86/speculation: Unify conditional spectre v2 print functions Thomas Gleixner
2018-11-28 14:29   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 17/28] x86/speculation: Add command line control for indirect branch speculation Thomas Gleixner
2018-11-28 14:29   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 18/28] x86/speculation: Prepare for per task indirect branch speculation control Thomas Gleixner
2018-11-27 17:25   ` Lendacky, Thomas
2018-11-27 19:51     ` Tim Chen
2018-11-28  9:39       ` Thomas Gleixner
2018-11-27 20:39     ` Thomas Gleixner
2018-11-27 20:42       ` Thomas Gleixner
2018-11-27 21:52         ` Lendacky, Thomas
2018-11-28 14:30   ` [tip:x86/pti] " tip-bot for Tim Chen
2018-11-25 18:33 ` [patch V2 19/28] x86/process: Consolidate and simplify switch_to_xtra() code Thomas Gleixner
2018-11-26 18:30   ` Borislav Petkov
2018-11-28 14:30   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 20/28] x86/speculation: Avoid __switch_to_xtra() calls Thomas Gleixner
2018-11-28 14:31   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` Thomas Gleixner [this message]
2018-11-25 19:11   ` [patch V2 21/28] x86/speculation: Prepare for conditional IBPB in switch_mm() Thomas Gleixner
2018-11-25 20:53   ` Andi Kleen
2018-11-25 22:20     ` Thomas Gleixner
2018-11-25 23:04       ` Andy Lutomirski
2018-11-26  7:10         ` Thomas Gleixner
2018-11-26 13:36           ` Ingo Molnar
2018-11-26  3:07       ` Andi Kleen
2018-11-26  6:50         ` Thomas Gleixner
2018-11-28 14:31   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 22/28] ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS Thomas Gleixner
2018-11-28 14:32   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 23/28] x86/speculation: Split out TIF update Thomas Gleixner
2018-11-28 14:33   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 24/28] x86/speculation: Prepare arch_smt_update() for PRCTL mode Thomas Gleixner
2018-11-27 20:18   ` Lendacky, Thomas
2018-11-27 20:30     ` Thomas Gleixner
2018-11-27 21:20       ` Lendacky, Thomas
2018-11-28 14:34   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 25/28] x86/speculation: Add prctl() control for indirect branch speculation Thomas Gleixner
2018-11-28 14:34   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 26/28] x86/speculation: Enable prctl mode for spectre_v2_user Thomas Gleixner
2018-11-26  7:56   ` Dominik Brodowski
2018-11-28 14:35   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-25 18:33 ` [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode Thomas Gleixner
2018-11-25 19:35   ` Randy Dunlap
2018-11-25 20:40   ` Linus Torvalds
2018-11-25 20:52     ` Jiri Kosina
2018-11-25 22:28     ` Thomas Gleixner
2018-11-26 13:30       ` Ingo Molnar
2018-11-26 20:48       ` Andrea Arcangeli
2018-11-26 20:58         ` Thomas Gleixner
2018-11-26 21:52           ` Lendacky, Thomas
2018-11-27  0:37             ` Tim Chen
2018-12-04  1:38     ` Tim Chen
2018-12-04  8:39       ` Jiri Kosina
2018-12-04  9:43         ` Arjan van de Ven
2018-12-04  9:46         ` Arjan van de Ven
2018-12-04 17:20       ` Linus Torvalds
2018-12-04 18:58         ` Tim Chen
2018-11-28 14:35   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-12-04 18:45   ` [patch V2 27/28] " Dave Hansen
2018-11-25 18:33 ` [patch V2 28/28] x86/speculation: Provide IBPB always command line options Thomas Gleixner
2018-11-28 14:36   ` [tip:x86/pti] " tip-bot for Thomas Gleixner
2018-11-26 13:37 ` [patch V2 00/28] x86/speculation: Remedy the STIBP/IBPB overhead Ingo Molnar
2018-11-28 14:24 ` Thomas Gleixner
2018-11-29 19:02   ` Tim Chen
2018-12-10 23:43 ` Pavel Machek

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Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git