diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2018-05-12 20:10:00 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-22 16:58:04 +0200 |
| commit | 0ec827f974e198c609c2f258a5a1f11f9af48bb2 (patch) | |
| tree | bbf71619b8d0fe9d9303cb8e3956c21441ec98de /arch/x86/kernel | |
| parent | ec90464d96c50f90bfe1bde6dea748a6c962313c (diff) | |
x86/bugs: Rework spec_ctrl base and mask logic
commit be6fcb5478e95bb1c91f489121238deb3abca46a upstream
x86_spec_ctrL_mask is intended to mask out bits from a MSR_SPEC_CTRL value
which are not to be modified. However the implementation is not really used
and the bitmask was inverted to make a check easier, which was removed in
"x86/bugs: Remove x86_spec_ctrl_set()"
Aside of that it is missing the STIBP bit if it is supported by the
platform, so if the mask would be used in x86_virt_spec_ctrl() then it
would prevent a guest from setting STIBP.
Add the STIBP bit if supported and use the mask in x86_virt_spec_ctrl() to
sanitize the value which is supplied by the guest.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 82a99d00563e..2ae358668ab8 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -41,7 +41,7 @@ EXPORT_SYMBOL_GPL(x86_spec_ctrl_base); * The vendor and possibly platform specific bits which can be modified in * x86_spec_ctrl_base. */ -static u64 __ro_after_init x86_spec_ctrl_mask = ~SPEC_CTRL_IBRS; +static u64 __ro_after_init x86_spec_ctrl_mask = SPEC_CTRL_IBRS; /* * AMD specific MSR info for Speculative Store Bypass control. @@ -67,6 +67,10 @@ void __init check_bugs(void) if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); + /* Allow STIBP in MSR_SPEC_CTRL if supported */ + if (boot_cpu_has(X86_FEATURE_STIBP)) + x86_spec_ctrl_mask |= SPEC_CTRL_STIBP; + /* Select the proper spectre mitigation before patching alternatives */ spectre_v2_select_mitigation(); @@ -135,18 +139,26 @@ static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = void x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) { + u64 msrval, guestval, hostval = x86_spec_ctrl_base; struct thread_info *ti = current_thread_info(); - u64 msr, host = x86_spec_ctrl_base; /* Is MSR_SPEC_CTRL implemented ? */ if (static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) { + /* + * Restrict guest_spec_ctrl to supported values. Clear the + * modifiable bits in the host base value and or the + * modifiable bits from the guest value. + */ + guestval = hostval & ~x86_spec_ctrl_mask; + guestval |= guest_spec_ctrl & x86_spec_ctrl_mask; + /* SSBD controlled in MSR_SPEC_CTRL */ if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD)) - host |= ssbd_tif_to_spec_ctrl(ti->flags); + hostval |= ssbd_tif_to_spec_ctrl(ti->flags); - if (host != guest_spec_ctrl) { - msr = setguest ? guest_spec_ctrl : host; - wrmsrl(MSR_IA32_SPEC_CTRL, msr); + if (hostval != guestval) { + msrval = setguest ? guestval : hostval; + wrmsrl(MSR_IA32_SPEC_CTRL, msrval); } } } @@ -492,7 +504,7 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void) switch (boot_cpu_data.x86_vendor) { case X86_VENDOR_INTEL: x86_spec_ctrl_base |= SPEC_CTRL_SSBD; - x86_spec_ctrl_mask &= ~SPEC_CTRL_SSBD; + x86_spec_ctrl_mask |= SPEC_CTRL_SSBD; wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); break; case X86_VENDOR_AMD: |