Merge tag 'x86_cpu_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cpu updates from Borislav Petkov:

 - Start checking a CPUID bit on AMD Zen3 which states that the CPU
   clears the segment base when a null selector is written. Do the
   explicit detection on older CPUs, zen2 and hygon specifically, which
   have the functionality but do not advertize the CPUID bit. Factor in
   the presence of a hypervisor underneath the kernel and avoid doing
   the explicit check there which the HV might've decided to not
   advertize for migration safety reasons, or similar.

 - Add support for a new X86 CPU vendor: VORTEX. Needed for whitelisting
   those CPUs in the hardware vulnerabilities detection

 - Force the compiler to use rIP-relative addressing in the fallback
   path of static_cpu_has(), in order to avoid unnecessary register
   pressure

* tag 'x86_cpu_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu: Fix migration safety with X86_BUG_NULL_SEL
  x86/CPU: Add support for Vortex CPUs
  x86/umip: Downgrade warning messages to debug loglevel
  x86/asm: Avoid adding register pressure for the init case in static_cpu_has()
  x86/asm: Add _ASM_RIP() macro for x86-64 (%rip) suffix

1 files changed, 39 insertions, 7 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8ed18d00c211..0083464de5e3 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1048,6 +1048,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
 	VULNWL(CENTAUR,	5, X86_MODEL_ANY,	NO_SPECULATION),
 	VULNWL(INTEL,	5, X86_MODEL_ANY,	NO_SPECULATION),
 	VULNWL(NSC,	5, X86_MODEL_ANY,	NO_SPECULATION),
+	VULNWL(VORTEX,	5, X86_MODEL_ANY,	NO_SPECULATION),
+	VULNWL(VORTEX,	6, X86_MODEL_ANY,	NO_SPECULATION),
 
 	/* Intel Family 6 */
 	VULNWL_INTEL(ATOM_SALTWELL,		NO_SPECULATION | NO_ITLB_MULTIHIT),
@@ -1399,9 +1401,8 @@ void __init early_cpu_init(void)
 	early_identify_cpu(&boot_cpu_data);
 }
 
-static void detect_null_seg_behavior(struct cpuinfo_x86 *c)
+static bool detect_null_seg_behavior(void)
 {
-#ifdef CONFIG_X86_64
 	/*
 	 * Empirically, writing zero to a segment selector on AMD does
 	 * not clear the base, whereas writing zero to a segment
@@ -1422,10 +1423,43 @@ static void detect_null_seg_behavior(struct cpuinfo_x86 *c)
 	wrmsrl(MSR_FS_BASE, 1);
 	loadsegment(fs, 0);
 	rdmsrl(MSR_FS_BASE, tmp);
-	if (tmp != 0)
-		set_cpu_bug(c, X86_BUG_NULL_SEG);
 	wrmsrl(MSR_FS_BASE, old_base);
-#endif
+	return tmp == 0;
+}
+
+void check_null_seg_clears_base(struct cpuinfo_x86 *c)
+{
+	/* BUG_NULL_SEG is only relevant with 64bit userspace */
+	if (!IS_ENABLED(CONFIG_X86_64))
+		return;
+
+	/* Zen3 CPUs advertise Null Selector Clears Base in CPUID. */
+	if (c->extended_cpuid_level >= 0x80000021 &&
+	    cpuid_eax(0x80000021) & BIT(6))
+		return;
+
+	/*
+	 * CPUID bit above wasn't set. If this kernel is still running
+	 * as a HV guest, then the HV has decided not to advertize
+	 * that CPUID bit for whatever reason.	For example, one
+	 * member of the migration pool might be vulnerable.  Which
+	 * means, the bug is present: set the BUG flag and return.
+	 */
+	if (cpu_has(c, X86_FEATURE_HYPERVISOR)) {
+		set_cpu_bug(c, X86_BUG_NULL_SEG);
+		return;
+	}
+
+	/*
+	 * Zen2 CPUs also have this behaviour, but no CPUID bit.
+	 * 0x18 is the respective family for Hygon.
+	 */
+	if ((c->x86 == 0x17 || c->x86 == 0x18) &&
+	    detect_null_seg_behavior())
+		return;
+
+	/* All the remaining ones are affected */
+	set_cpu_bug(c, X86_BUG_NULL_SEG);
 }
 
 static void generic_identify(struct cpuinfo_x86 *c)
@@ -1461,8 +1495,6 @@ static void generic_identify(struct cpuinfo_x86 *c)
 
 	get_model_name(c); /* Default name */
 
-	detect_null_seg_behavior(c);
-
 	/*
 	 * ESPFIX is a strange bug.  All real CPUs have it.  Paravirt
 	 * systems that run Linux at CPL > 0 may or may not have the