From: Boris Petkov <bp@alien8.de>
To: Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org
Cc: pawan.kumar.gupta@linux.intel.com,
antonio.gomez.iglesias@linux.intel.com,
linux-doc@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/speculation: Add BHI_DIS support
Date: Thu, 14 Jul 2022 19:58:08 +0000 [thread overview]
Message-ID: <7D1E33F3-A390-4691-86C2-F7CB3E8309B3@alien8.de> (raw)
In-Reply-To: <20220714195236.9311-1-daniel.sneddon@linux.intel.com>
On July 14, 2022 7:52:35 PM UTC, Daniel Sneddon <daniel.sneddon@linux.intel.com> wrote:
>Branch History Injection (BHI) attacks can be mitigated using the
>BHI_DIS_S indirect predictor control bit located in MSR_IA32_SPEC_CTRL
>register. Set BHI_DIS in MSR_IA32_SPC_CTRL to prevent predicted
>targets of indirect branches executed in CPL0, CPL1, or CPL2 from
>being selected based on branch history from branches executed in CPL3.
>Support for this feature is enumerated by CPUID.7.2.EDX[BHI_CTRL] (bit 4).
>
>Users wanting BHI protection can specify spectre_v2=eibrs,bhi_dis to
>enable hardware BHI protections. On platforms where BHI protections
>are not available in the hardware revert to eibrs,retpoline
>mitigations.
Why is this a separately selectable option and not automatically enabled?
--
Sent from a small device: formatting sux and brevity is inevitable.
next prev parent reply other threads:[~2022-07-14 19:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 19:52 [PATCH] x86/speculation: Add BHI_DIS support Daniel Sneddon
2022-07-14 19:58 ` Boris Petkov [this message]
2022-07-14 20:04 ` Peter Zijlstra
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