| From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> |
| Date: Wed, 25 Apr 2018 22:04:23 -0400 |
| Subject: x86/bugs: Whitelist allowed SPEC_CTRL MSR values |
| |
| commit 1115a859f33276fe8afb31c60cf9d8e657872558 upstream. |
| |
| Intel and AMD SPEC_CTRL (0x48) MSR semantics may differ in the |
| future (or in fact use different MSRs for the same functionality). |
| |
| As such a run-time mechanism is required to whitelist the appropriate MSR |
| values. |
| |
| [ tglx: Made the variable __ro_after_init ] |
| |
| Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Reviewed-by: Ingo Molnar <mingo@kernel.org> |
| [bwh: Backported to 3.16: |
| - We don't have __ro_after_init |
| - Adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| arch/x86/kernel/cpu/bugs.c | 11 +++++++++-- |
| 1 file changed, 9 insertions(+), 2 deletions(-) |
| |
| --- a/arch/x86/kernel/cpu/bugs.c |
| +++ b/arch/x86/kernel/cpu/bugs.c |
| @@ -34,6 +34,12 @@ static void __init ssb_select_mitigation |
| */ |
| static u64 x86_spec_ctrl_base; |
| |
| +/* |
| + * The vendor and possibly platform specific bits which can be modified in |
| + * x86_spec_ctrl_base. |
| + */ |
| +static u64 x86_spec_ctrl_mask = ~SPEC_CTRL_IBRS; |
| + |
| #ifdef CONFIG_X86_32 |
| |
| static double __initdata x = 4195835.0; |
| @@ -179,7 +185,7 @@ static enum spectre_v2_mitigation spectr |
| |
| void x86_spec_ctrl_set(u64 val) |
| { |
| - if (val & ~(SPEC_CTRL_IBRS | SPEC_CTRL_RDS)) |
| + if (val & x86_spec_ctrl_mask) |
| WARN_ONCE(1, "SPEC_CTRL MSR value 0x%16llx is unknown.\n", val); |
| else |
| wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base | val); |
| @@ -497,6 +503,7 @@ static enum ssb_mitigation_cmd __init __ |
| switch (boot_cpu_data.x86_vendor) { |
| case X86_VENDOR_INTEL: |
| x86_spec_ctrl_base |= SPEC_CTRL_RDS; |
| + x86_spec_ctrl_mask &= ~SPEC_CTRL_RDS; |
| x86_spec_ctrl_set(SPEC_CTRL_RDS); |
| break; |
| case X86_VENDOR_AMD: |
| @@ -520,7 +527,7 @@ static void ssb_select_mitigation() |
| void x86_spec_ctrl_setup_ap(void) |
| { |
| if (boot_cpu_has(X86_FEATURE_IBRS)) |
| - x86_spec_ctrl_set(x86_spec_ctrl_base & (SPEC_CTRL_IBRS | SPEC_CTRL_RDS)); |
| + x86_spec_ctrl_set(x86_spec_ctrl_base & ~x86_spec_ctrl_mask); |
| } |
| |
| #ifdef CONFIG_SYSFS |
