linux-kernel - [PATCH 3.16 064/410] x86/speculation: Correct Speculation Control microcode blacklist again

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Message-ID: <lsq.1528380321.777858732@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Peter Zijlstra" <peterz@...radead.org>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        "Borislav Petkov" <bp@...en8.de>, "Ingo Molnar" <mingo@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>, pbonzini@...hat.com,
        kvm@...r.kernel.org,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Arjan van de Ven" <arjan@...ux.intel.com>,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "David Woodhouse" <dwmw2@...radead.org>,
        "Andy Lutomirski" <luto@...nel.org>,
        "Arjan van de Ven" <arjan.van.de.ven@...el.com>,
        "Dan Williams" <dan.j.williams@...el.com>, dave.hansen@...el.com
Subject: [PATCH 3.16 064/410] x86/speculation: Correct Speculation Control
 microcode blacklist  again

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Woodhouse <dwmw@...zon.co.uk>

commit d37fc6d360a404b208547ba112e7dabb6533c7fc upstream.

Arjan points out that the Intel document only clears the 0xc2 microcode
on *some* parts with CPUID 506E3 (INTEL_FAM6_SKYLAKE_DESKTOP stepping 3).
For the Skylake H/S platform it's OK but for Skylake E3 which has the
same CPUID it isn't (yet) cleared.

So removing it from the blacklist was premature. Put it back for now.

Also, Arjan assures me that the 0x84 microcode for Kaby Lake which was
featured in one of the early revisions of the Intel document was never
released to the public, and won't be until/unless it is also validated
as safe. So those can change to 0x80 which is what all *other* versions
of the doc have identified.

Once the retrospective testing of existing public microcodes is done, we
should be back into a mode where new microcodes are only released in
batches and we shouldn't even need to update the blacklist for those
anyway, so this tweaking of the list isn't expected to be a thing which
keeps happening.

Requested-by: Arjan van de Ven <arjan.van.de.ven@...el.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: arjan.van.de.ven@...el.com
Cc: dave.hansen@...el.com
Cc: kvm@...r.kernel.org
Cc: pbonzini@...hat.com
Link: http://lkml.kernel.org/r/1518449255-2182-1-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/cpu/intel.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -40,13 +40,14 @@ struct sku_microcode {
 	u32 microcode;
 };
 static const struct sku_microcode spectre_bad_microcodes[] = {
-	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0B,	0x84 },
-	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0A,	0x84 },
-	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x09,	0x84 },
-	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x0A,	0x84 },
-	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x09,	0x84 },
+	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0B,	0x80 },
+	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0A,	0x80 },
+	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x09,	0x80 },
+	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x0A,	0x80 },
+	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x09,	0x80 },
 	{ INTEL_FAM6_SKYLAKE_X,		0x03,	0x0100013e },
 	{ INTEL_FAM6_SKYLAKE_X,		0x04,	0x0200003c },
+	{ INTEL_FAM6_SKYLAKE_DESKTOP,	0x03,	0xc2 },
 	{ INTEL_FAM6_BROADWELL_CORE,	0x04,	0x28 },
 	{ INTEL_FAM6_BROADWELL_GT3E,	0x01,	0x1b },
 	{ INTEL_FAM6_BROADWELL_XEON_D,	0x02,	0x14 },