From nobody Wed Dec 17 06:10:12 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A26BA329388 for ; Fri, 14 Nov 2025 15:03:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763132641; cv=none; b=hoJIENokA1Z0beraaczDVXlBrWyn2Vs2YN0lD3Hq4q0J8AaKu6nmy+xDvUq5TknAMZKj8Eog4/WB3YGg/sjAOqmhNUmgm4B0CygLgwczsHFA6vwoQMNB6vwoAXIe4ALmjwAvN8tIoUqyptPxIoyD5HsiNTFkGEKD+yO2yb+/ywE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763132641; c=relaxed/simple; bh=xCMOlKiIGKnSNkXBmGdxZOf4glAFhGzcKWNIOlI6Uso=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VMKRi+1Ff69TDTx+ASxhti21TWdhhV90F0kBrT1OWs4VmCECKkrUfvXHtaljm3bcYPt4TCITc7GwGol6Vl25Hnw2hFwKscxeJr+NTGJrhBk5WYoMboqGF3l+fFdnwJxzK0leKY4o/gLuIvGMBaWatmbiil6YjoR2q9ud1AIF+TY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=A/hWveJr; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="A/hWveJr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763132638; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fSiRQxA5I7cbtbKutRpvTlGvB/h9JsDFAWOVN0dt9w8=; b=A/hWveJrAAWkHlXCvzMB08ItOsxCxOKzvT5q2ickctlboQmz0OaehJeBvdQM5BP+4HZ+0T mnqnSZnGL+SxYefhtHyvXUKGj6gfBYrav0tKTe/npKhlAnM7+hXg1GCT6+I4CVQfByBcFr orwgr4D83ubmcO1Zv5l6UbuN6BJVuxc= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-618-VO3NDkKcOP-dF92Nk4JHRQ-1; Fri, 14 Nov 2025 10:03:56 -0500 X-MC-Unique: VO3NDkKcOP-dF92Nk4JHRQ-1 X-Mimecast-MFC-AGG-ID: VO3NDkKcOP-dF92Nk4JHRQ_1763132631 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 54050180047F; Fri, 14 Nov 2025 15:03:50 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.45.226.10]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 694CE1955F43; Fri, 14 Nov 2025 15:03:35 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , Shrikanth Hegde Subject: [PATCH v7 06/31] static_call: Add read-only-after-init static calls Date: Fri, 14 Nov 2025 16:01:08 +0100 Message-ID: <20251114150133.1056710-7-vschneid@redhat.com> In-Reply-To: <20251114150133.1056710-1-vschneid@redhat.com> References: <20251114150133.1056710-1-vschneid@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" From: Josh Poimboeuf Deferring a code patching IPI is unsafe if the patched code is in a noinstr region. In that case the text poke code must trigger an immediate IPI to all CPUs, which can rudely interrupt an isolated NO_HZ CPU running in userspace. If a noinstr static call only needs to be patched during boot, its key can be made ro-after-init to ensure it will never be patched at runtime. Signed-off-by: Josh Poimboeuf --- include/linux/static_call.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/include/linux/static_call.h b/include/linux/static_call.h index 78a77a4ae0ea8..ea6ca57e2a829 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -192,6 +192,14 @@ extern long __static_call_return0(void); }; \ ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func) =20 +#define DEFINE_STATIC_CALL_RO(name, _func) \ + DECLARE_STATIC_CALL(name, _func); \ + struct static_call_key __ro_after_init STATIC_CALL_KEY(name) =3D {\ + .func =3D _func, \ + .type =3D 1, \ + }; \ + ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func) + #define DEFINE_STATIC_CALL_NULL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) =3D { \ @@ -200,6 +208,14 @@ extern long __static_call_return0(void); }; \ ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) =20 +#define DEFINE_STATIC_CALL_NULL_RO(name, _func) \ + DECLARE_STATIC_CALL(name, _func); \ + struct static_call_key __ro_after_init STATIC_CALL_KEY(name) =3D {\ + .func =3D NULL, \ + .type =3D 1, \ + }; \ + ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) + #define DEFINE_STATIC_CALL_RET0(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) =3D { \ --=20 2.51.0