diff options
authorThomas Gleixner <tglx@linutronix.de>2018-04-30 21:47:46 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-05-02 16:44:38 +0200
commitc65732e4f72124ca5a3a0dd3bee0d3cee39c7170 (patch)
parent6da6c0db5316275015e8cc2959f12a17584aeb64 (diff)
x86/cpu: Restore CPUID_8000_0008_EBX reload
The recent commt which addresses the x86_phys_bits corruption with encrypted memory on CPUID reload after a microcode update lost the reload of CPUID_8000_0008_EBX as well. As a consequence IBRS and IBRS_FW are not longer detected Restore the behaviour by bringing the reload of CPUID_8000_0008_EBX back. This restore has a twist due to the convoluted way the cpuid analysis works: CPUID_8000_0008_EBX is used by AMD to enumerate IBRB, IBRS, STIBP. On Intel EBX is not used. But the speculation control code sets the AMD bits when running on Intel depending on the Intel specific speculation control bits. This was done to use the same bits for alternatives. The change which moved the 8000_0008 evaluation out of get_cpu_cap() broke this nasty scheme due to ordering. So that on Intel the store to CPUID_8000_0008_EBX clears the IBRB, IBRS, STIBP bits which had been set before by software. So the actual CPUID_8000_0008_EBX needs to go back to the place where it was and the phys/virt address space calculation cannot touch it. In hindsight this should have used completely synthetic bits for IBRB, IBRS, STIBP instead of reusing the AMD bits, but that's for 4.18. /me needs to find time to cleanup that steaming pile of ... Fixes: d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment corruption") Reported-by: Jörg Otte <jrg.otte@gmail.com> Reported-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jörg Otte <jrg.otte@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: kirill.shutemov@linux.intel.com Cc: Borislav Petkov <bp@alien8.de Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1805021043510.1668@nanos.tec.linutronix.de
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8a5b185735e1..ce243f7d2d4e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -848,6 +848,11 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
c->x86_power = edx;
+ if (c->extended_cpuid_level >= 0x80000008) {
+ cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
+ c->x86_capability[CPUID_8000_0008_EBX] = ebx;
+ }
if (c->extended_cpuid_level >= 0x8000000a)
c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
@@ -871,7 +876,6 @@ static void get_cpu_address_sizes(struct cpuinfo_x86 *c)
c->x86_virt_bits = (eax >> 8) & 0xff;
c->x86_phys_bits = eax & 0xff;
- c->x86_capability[CPUID_8000_0008_EBX] = ebx;
#ifdef CONFIG_X86_32
else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))