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Date: Fri, 26 Jan 2018 18:27:12 +0100
From: Borislav Petkov <bp@suse.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Liran Alon <liran.alon@oracle.com>,
	Laura Abbott <labbott@redhat.com>,
	Andrew Lutomirski <luto@kernel.org>,
	Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>,
	"Mallick, Asit K" <asit.k.mallick@intel.com>,
	Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
	KarimAllah Ahmed <karahmed@amazon.de>, Peter Anvin <hpa@zytor.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	Ashok Raj <ashok.raj@intel.com>,
	"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
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	Dan Williams <dan.j.williams@intel.com>,
	Joerg Roedel <joro@8bytes.org>,
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	KVM list <kvm@vger.kernel.org>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict
 Indirect Branch Speculation
Message-ID: <20180126172712.e6iznttrqzfnwxyw@pd.tnic>
References: <7c0b0879-3448-43e4-8380-4708fc787113@default>
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 <1516957886.30244.161.camel@infradead.org>
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On Fri, Jan 26, 2018 at 09:19:09AM -0800, Linus Torvalds wrote:
> But did we do that "disable stuffing with SMEP"? I'm not seeing it. In
> my tree, it's only conditional on X86_FEATURE_RETPOLINE.

Or rather, enable stuffing on !SMEP:

+       if ((!boot_cpu_has(X86_FEATURE_PTI) &&
+            !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
+               setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
+               pr_info("Filling RSB on context switch\n");
+       }

Should be

c995efd5a740 ("x86/retpoline: Fill RSB on context switch for affected CPUs")

in your tree.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--