x86/bugs: Update when to check for the LS_CFG SSBD mitigation

If either the X86_FEATURE_AMD_SSBD or X86_FEATURE_VIRT_SSBD features are
present, then there is no need to perform the check for the LS_CFG SSBD
mitigation support.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180702213553.29202.21089.stgit@tlendack-t1.amdoffice.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
CVE-2018-3639

(cherry picked from commit 845d382bb15c6e7dc5026c0ff919c5b13fc7e11b)
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 2cc30f34d525c12c88448fd9e5b48b110b4ab42a..3d7fa07b69bb19033b997f120dc89710d1b2ced8 100644 (file)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -549,7 +549,9 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
                nodes_per_socket = ((value >> 3) & 7) + 1;
        }
 
-       if (c->x86 >= 0x15 && c->x86 <= 0x17) {
+       if (!boot_cpu_has(X86_FEATURE_AMD_SSBD) &&
+           !boot_cpu_has(X86_FEATURE_VIRT_SSBD) &&
+           c->x86 >= 0x15 && c->x86 <= 0x17) {
                unsigned int bit;
 
                switch (c->x86) {