From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: Tom Lendacky <thomas.lendacky@amd.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"andi@firstfloor.org" <andi@firstfloor.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"pjt@google.com" <pjt@google.com>,
"luto@kernel.org" <luto@kernel.org>,
"dave.hansen@intel.com" <dave.hansen@intel.com>,
"jikos@kernel.org" <jikos@kernel.org>,
"gregkh@linux-foundation.org" <gregkh@linux-foundation.org>
Subject: Re: [PATCH v3 3/3] x86/retpoline: Convert generic specific retpolines to use RETPOLINE_GENERIC
Date: Wed, 10 Jan 2018 14:46:34 +0000 [thread overview]
Message-ID: <1515595594.22302.170.camel@amazon.co.uk> (raw)
In-Reply-To: <e17565b1-3f51-3739-b788-d73063454436@amd.com>
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On Wed, 2018-01-10 at 08:23 -0600, Tom Lendacky wrote:
> On 1/10/2018 7:15 AM, Woodhouse, David wrote:
> > On Tue, 2018-01-09 at 18:28 -0800, Andi Kleen wrote:
> >> From: Andi Kleen <ak@linux.intel.com>
> >>
> >> X86_FEATURE_RETPOLINE has been renamed to X86_FEATURE_RETPOLINE_GENERIC.
> >> Convert the sequences using it.
> >
> > AMD documentation says they need the RSB fill too, so these should stay
> > under X86_FEATURE_RETPOLINE I think.
>
> AMD processors don't fall back to the indirect predictor on an underflow
> so this isn't needed on AMD if it is purely for underflow prevention.
It isn't purely for underflow protection. This is needed (see the AMD
doc) for protecting against RSB entries that actually point to
userspace addresses. It's only not needed if we have SMEP.
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next prev parent reply other threads:[~2018-01-10 14:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-10 2:28 Update retpoline boot fix Andi Kleen
2018-01-10 2:28 ` [PATCH v3 1/3] x86/retpoline: Add X86_FEATURE_RETPOLINE_GENERIC Andi Kleen
2018-01-10 2:28 ` [PATCH v3 2/3] x86/retpoline: Use better sequences for NOSPEC_CALL/JMP Andi Kleen
2018-01-10 13:26 ` Woodhouse, David
2018-01-10 2:28 ` [PATCH v3 3/3] x86/retpoline: Convert generic specific retpolines to use RETPOLINE_GENERIC Andi Kleen
2018-01-10 13:15 ` Woodhouse, David
2018-01-10 14:23 ` Tom Lendacky
2018-01-10 14:46 ` Woodhouse, David [this message]
2018-01-10 15:18 ` Tom Lendacky
2018-01-10 15:20 ` Woodhouse, David
2018-01-10 10:41 ` Update retpoline boot fix Thomas Gleixner
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