diff options
| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2018-04-25 22:04:19 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-22 16:57:59 +0200 |
| commit | cf21f58ae6f264e0a10d9736be97342627cf9837 (patch) | |
| tree | a034219c26f05bafdceb6363388f5427503a2b84 /arch/x86/include | |
| parent | 0f5dd651397b264903e8becc511af6cf384c273e (diff) | |
x86/bugs, KVM: Support the combination of guest and host IBRS
commit 5cf687548705412da47c9cec342fd952d71ed3d5 upstream
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>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 9ec3d4d448cd..d1c2630922da 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -228,6 +228,16 @@ enum spectre_v2_mitigation { extern void x86_spec_ctrl_set(u64); extern u64 x86_spec_ctrl_get_default(void); +/* + * On VMENTER we must preserve whatever view of the SPEC_CTRL MSR + * the guest has, while on VMEXIT we restore the host view. This + * would be easier if SPEC_CTRL were architecturally maskable or + * shadowable for guests but this is not (currently) the case. + * Takes the guest view of SPEC_CTRL MSR as a parameter. + */ +extern void x86_spec_ctrl_set_guest(u64); +extern void x86_spec_ctrl_restore_host(u64); + extern char __indirect_thunk_start[]; extern char __indirect_thunk_end[]; |