From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <ak@linux.intel.com>
X-Google-Smtp-Source: AH8x227at7/K/+XnBf5sCGYi6aoS8QTLLVQCS/RXvC5asbuGJynaVrX5rA91uGzFkFo27dVhXaK0
ARC-Seal: i=1; a=rsa-sha256; t=1516747198; cv=none;
        d=google.com; s=arc-20160816;
        b=a80DZC+RY5OLpmeAhu1GFi7G0U7mgYU71YvaUjzmqH3O4Z6CIewbqoIjYLMkdY3XOz
         foqFIE508UkZ0lgPb0JK24+TBF36beKkcUC4r9Dzdf2ycyu+Ltqhk67ioMPDH5McT799
         U2njpI6STug4TKOBn0jEIZX88HaosvUUnL4HgVR8v7dGyGUt/dXh6uK9hBKUSppgaMc7
         B3n+A9L0Vsgn/6I64UecLWfoXg14j3fsFHI/YcQS9YtunJAtfNbPBU55LJDbTDtQGySm
         +1e2gXJX+sO4ls1GPKAbbfYj1g2IPjyOtZTQRfYoU+0EZTVcn5U9UAjD1zbULy84YC48
         Jz0Q==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=message-id:date:subject:cc:to:from:arc-authentication-results;
        bh=oubfqGI93nOov9jFlUfUVKdJfxTRlr+1ue0haCJXg4c=;
        b=LUiqtAzh0nZQ31Qd8Z2fWzXYslOwKZPSIFxOEeADaEnqLnuPmphUQGraDX9z0M6w/R
         cZ1iGPArnTn6rS762t/hisnlzOPt71V8f9ZaMEkfY6j48vfCvpUmOGwWlPW2MwUx/0s4
         4DdtpnSozNMXqLdcxpdYbMJloyA4DVez30AIDdl2g9F1vRsq3x0Opec5eeDPLF8MpsMX
         rYaHUj3sD1pc5nXWWNky2o+9tN5rSaPNDcbC5e6VQyMvWzEsXS57L7WEVzLS5ALdjgMx
         01VMv8tXyfPHsHrmSrfAzDas64e93Un7vph93gZeA6yZ2ESAaj1y6C3W8xcnz3qAZTtd
         hjVg==
ARC-Authentication-Results: i=1; mx.google.com;
       spf=pass (google.com: best guess record for domain of ak@linux.intel.com designates 192.55.52.115 as permitted sender) smtp.mailfrom=ak@linux.intel.com
Authentication-Results: mx.google.com;
       spf=pass (google.com: best guess record for domain of ak@linux.intel.com designates 192.55.52.115 as permitted sender) smtp.mailfrom=ak@linux.intel.com
X-Amp-Result: SKIPPED(no attachment in message)
X-Amp-File-Uploaded: False
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.46,403,1511856000";
   d="scan'208";a="198105958"
From: Andi Kleen <andi@firstfloor.org>
To: tglx@linutronix.de
Cc: dwmw@amazon.co.uk,
	thomas.lendacky@amd.com,
	peterz@infradead.org,
	torvalds@linux-foundation.org,
	luto@amacapital.net,
	x86@kernel.org,
	gregkh@linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Support interrupt stuffing for Skylake
Date: Tue, 23 Jan 2018 14:39:14 -0800
Message-Id: <20180123223916.26904-1-andi@firstfloor.org>
X-Mailer: git-send-email 2.14.3
X-getmail-retrieved-from-mailbox: INBOX
X-GMAIL-THRID: =?utf-8?q?1590424711385475238?=
X-GMAIL-MSGID: =?utf-8?q?1590424711385475238?=
X-Mailing-List: linux-kernel@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>

Skylake with retpoline needs additional protection against return
stack underflows. While full coverage is more involved, there
are some low hanging fruits that are relatively easy.  We already
did stuffing on context switch earlier, this adds the next
low hanging fruit: stuffing on interrupts and exception return
to the kernel. 

We only need to stuff when returning to the kernel so there is
no impact on anything interrupting user space directly. Also the
additional stuffing is only enabled on Skylake.

Git tree available here
git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git spec/interrupt-stuff-1

v1: Initial post, but based on the earlier skl-rsb code.