linux-kernel - Re: [RFC PATCH v3 12/15] context_tracking,x86: Defer kernel text patching IPIs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241120151308.GL19989@noisy.programming.kicks-ass.net>
Date: Wed, 20 Nov 2024 16:13:08 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Valentin Schneider <vschneid@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	kvm@...r.kernel.org, linux-mm@...ck.org, bpf@...r.kernel.org,
	x86@...nel.org, rcu@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Nicolas Saenz Julienne <nsaenzju@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	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>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Wanpeng Li <wanpengli@...cent.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Jason Baron <jbaron@...mai.com>, Kees Cook <keescook@...omium.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Nicholas Piggin <npiggin@...il.com>,
	Juerg Haefliger <juerg.haefliger@...onical.com>,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Nadav Amit <namit@...are.com>, Dan Carpenter <error27@...il.com>,
	Chuang Wang <nashuiliang@...il.com>,
	Yang Jihong <yangjihong1@...wei.com>,
	Petr Mladek <pmladek@...e.com>,
	"Jason A. Donenfeld" <Jason@...c4.com>, Song Liu <song@...nel.org>,
	Julian Pidancet <julian.pidancet@...cle.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Dionna Glaze <dionnaglaze@...gle.com>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Juri Lelli <juri.lelli@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Yair Podemsky <ypodemsk@...hat.com>,
	Daniel Wagner <dwagner@...e.de>, Petr Tesarik <ptesarik@...e.com>
Subject: Re: [RFC PATCH v3 12/15] context_tracking,x86: Defer kernel text
 patching IPIs

On Tue, Nov 19, 2024 at 04:34:59PM +0100, Valentin Schneider wrote:

> +static void __text_poke_sync(smp_cond_func_t cond_func)
> +{
> +	on_each_cpu_cond(cond_func, do_sync_core, NULL, 1);
> +}
> +
>  void text_poke_sync(void)
>  {
> -	on_each_cpu(do_sync_core, NULL, 1);
> +	__text_poke_sync(NULL);
> +}
> +
> +void text_poke_sync_deferrable(void)
> +{
> +	__text_poke_sync(do_sync_core_defer_cond);
>  }

How about we unwrap some of that like so:

>  /*
> @@ -2257,6 +2273,8 @@ static int tp_vec_nr;
>  static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
>  {
>  	unsigned char int3 = INT3_INSN_OPCODE;
> +	bool force_ipi = false;
> +	void (*sync_fn)(void);

	smp_cond_func_t cond = do_sync_core_defer_cond;

>  	unsigned int i;
>  	int do_sync;
>  
> @@ -2291,11 +2309,18 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
>  	 * First step: add a int3 trap to the address that will be patched.
>  	 */
>  	for (i = 0; i < nr_entries; i++) {
> +		/*
> +		 * Record that we need to send the IPI if at least one location
> +		 * in the batch requires it.
> +		 */
> +		force_ipi |= tp[i].force_ipi;

		if (tp[i].force_ipi)
			cond = NULL;

>  		tp[i].old = *(u8 *)text_poke_addr(&tp[i]);
>  		text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE);
>  	}
>  
> -	text_poke_sync();
> +	sync_fn = force_ipi ? text_poke_sync : text_poke_sync_deferrable;
> +
> +	sync_fn();

	__text_poke_sync(cond);