[PATCH 4.4 189/266] x86/bugs: Switch the selection of mitigation from CPU vendor to CPU features

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

commit 108fab4b5c8f12064ef86e02cb0459992affb30f upstream.

Both AMD and Intel can have SPEC_CTRL_MSR for SSBD.

However AMD also has two more other ways of doing it - which
are !SPEC_CTRL MSR ways.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: kvm@vger.kernel.org
Cc: KarimAllah Ahmed <karahmed@amazon.de>
Cc: andrew.cooper3@citrix.com
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lkml.kernel.org/r/20180601145921.9500-4-konrad.wilk@oracle.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/cpu/bugs.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -526,17 +526,12 @@ static enum ssb_mitigation __init __ssb_
 		 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
 		 * use a completely different MSR and bit dependent on family.
 		 */
-		switch (boot_cpu_data.x86_vendor) {
-		case X86_VENDOR_INTEL:
-		case X86_VENDOR_AMD:
-			if (!static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) {
-				x86_amd_ssb_disable();
-				break;
-			}
+		if (!static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
+			x86_amd_ssb_disable();
+		else {
 			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
 			x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
 			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
-			break;
 		}
 	}