diff options
| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2018-04-25 22:04:19 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-05-03 13:55:47 +0200 |
| commit | 5cf687548705412da47c9cec342fd952d71ed3d5 (patch) | |
| tree | 5b868ec35064f655e390b04a8ff520af0a660e7e /arch/x86/kernel | |
| parent | 1b86883ccb8d5d9506529d42dbe1a5257cb30b18 (diff) | |
x86/bugs, KVM: Support the combination of guest and host IBRS
A guest may modify the SPEC_CTRL MSR from the value used by the
kernel. Since the kernel doesn't use IBRS, this means a value of zero is
what is needed in the host.
But the 336996-Speculative-Execution-Side-Channel-Mitigations.pdf refers to
the other bits as reserved so the kernel should respect the boot time
SPEC_CTRL value and use that.
This allows to deal with future extensions to the SPEC_CTRL interface if
any at all.
Note: This uses wrmsrl() instead of native_wrmsl(). I does not make any
difference as paravirt will over-write the callq *0xfff.. with the wrmsrl
assembler code.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6ed84f50d74a..38a8626c894c 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -123,6 +123,24 @@ u64 x86_spec_ctrl_get_default(void) } EXPORT_SYMBOL_GPL(x86_spec_ctrl_get_default); +void x86_spec_ctrl_set_guest(u64 guest_spec_ctrl) +{ + if (!boot_cpu_has(X86_FEATURE_IBRS)) + return; + if (x86_spec_ctrl_base != guest_spec_ctrl) + wrmsrl(MSR_IA32_SPEC_CTRL, guest_spec_ctrl); +} +EXPORT_SYMBOL_GPL(x86_spec_ctrl_set_guest); + +void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl) +{ + if (!boot_cpu_has(X86_FEATURE_IBRS)) + return; + if (x86_spec_ctrl_base != guest_spec_ctrl) + wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); +} +EXPORT_SYMBOL_GPL(x86_spec_ctrl_restore_host); + #ifdef RETPOLINE static bool spectre_v2_bad_module; |