From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Sun, 7 Jan 2018 05:17:15 +0000 (-0500)
Subject: kpti: Disable when running under Xen PV
X-Git-Tag: v4.1.12-124.31.3~1299
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=7bd5f6122113ffa9b26d0df4c5a19bd429ad7181;p=users%2Fjedix%2Flinux-maple.git

kpti: Disable when running under Xen PV

Very very partial backport from aa8c6248f8c75 where
there is a check to see if this is an Xen PV guest - and
if so disable it.

The reason is that the PV ABI would require a major
overhaul to be Meltdown resistent.

Instead there are mitigations (PV in HVM) which are far more
suitable.

Orabug: 27333760
CVE: CVE-2017-5754

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>
---

diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 74eb971ea911..e978ae1c2a27 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -267,6 +267,9 @@ void __init kaiser_check_boottime_disable(void)
 	char arg[5];
 	int ret;
 
+	if (xen_pv_domain())
+		goto disable;
+
 	ret = cmdline_find_option(boot_command_line, "pti", arg, sizeof(arg));
 	if (ret > 0) {
 		if (!strncmp(arg, "on", 2))