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Date: Mon, 12 Feb 2024 20:53:28 -0800
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: Daniel Sneddon <daniel.sneddon@linux.intel.com>,
	antonio.gomez.iglesias@linux.intel.com,
	alyssa.milburn@linux.intel.com, andrew.cooper3@citrix.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] x86/bugs: Default retbleed to =stuff when retpoline
 is enabled
Message-ID: <20240213045328.3gdcjefbdwyjv3ll@desk>
References: <20240212-retbleed-auto-stuff-v2-1-89401649341a@linux.intel.com>
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In-Reply-To: <20240212-retbleed-auto-stuff-v2-1-89401649341a@linux.intel.com>

On Mon, Feb 12, 2024 at 05:23:21PM -0800, Pawan Gupta wrote:
> On Intel systems when retpoline mitigation is enabled for spectre-v2,
> retbleed=auto does not enable RSB stuffing. This may make the system
> vulnerable to retbleed. Retpoline is not the default mitigation when
> IBRS is present, but in virtualized cases a VMM can hide IBRS from
> guests, resulting in guest deploying retpoline by default. Even if IBRS
> is enumerated, a user can still select spectre_v2=retpoline.
> 
> As with other mitigations, mitigate retbleed by default. On Intel
> systems when retpoline is enabled, and retbleed mitigation is set to
> auto, enable Call Depth Tracking and RSB stuffing i.e. retbleed=stuff
> mitigation. For AMD/Hygon auto mode already selects the appropriate
> mitigation.

By mistake I sent this patch twice, please ignore the duplicate:

  https://lore.kernel.org/lkml/20240213042453.6j01GG4kjjcdTev7AtniyPHPRNH3RFHNGgVJ5nIXho4@z/