diff options
| author | Peter Zijlstra <[email protected]> | 2017-12-04 15:08:00 +0100 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2017-12-23 21:13:00 +0100 |
| commit | 21e94459110252d41b45c0c8ba50fd72a664d50c (patch) | |
| tree | 6324536045b00cccd293f9401207a6d43e2ab0f7 | |
| parent | 6fd166aae78c0ab738d49bda653cbd9e3b1491cf (diff) | |
x86/mm: Optimize RESTORE_CR3
Most NMI/paranoid exceptions will not in fact change pagetables and would
thus not require TLB flushing, however RESTORE_CR3 uses flushing CR3
writes.
Restores to kernel PCIDs can be NOFLUSH, because we explicitly flush the
kernel mappings and now that we track which user PCIDs need flushing we can
avoid those too when possible.
This does mean RESTORE_CR3 needs an additional scratch_reg, luckily both
sites have plenty available.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
| -rw-r--r-- | arch/x86/entry/calling.h | 30 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64.S | 4 |
2 files changed, 30 insertions, 4 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 7894e5c0eef7..45a63e00a6af 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -281,8 +281,34 @@ For 32-bit we have the following conventions - kernel is built with .Ldone_\@: .endm -.macro RESTORE_CR3 save_reg:req +.macro RESTORE_CR3 scratch_reg:req save_reg:req ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI + + ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID + + /* + * KERNEL pages can always resume with NOFLUSH as we do + * explicit flushes. + */ + bt $X86_CR3_PTI_SWITCH_BIT, \save_reg + jnc .Lnoflush_\@ + + /* + * Check if there's a pending flush for the user ASID we're + * about to set. + */ + movq \save_reg, \scratch_reg + andq $(0x7FF), \scratch_reg + bt \scratch_reg, THIS_CPU_user_pcid_flush_mask + jnc .Lnoflush_\@ + + btr \scratch_reg, THIS_CPU_user_pcid_flush_mask + jmp .Lwrcr3_\@ + +.Lnoflush_\@: + SET_NOFLUSH_BIT \save_reg + +.Lwrcr3_\@: /* * The CR3 write could be avoided when not changing its value, * but would require a CR3 read *and* a scratch register. @@ -301,7 +327,7 @@ For 32-bit we have the following conventions - kernel is built with .endm .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req .endm -.macro RESTORE_CR3 save_reg:req +.macro RESTORE_CR3 scratch_reg:req save_reg:req .endm #endif diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index fd501844af1f..ed31d00dc5ee 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1288,7 +1288,7 @@ ENTRY(paranoid_exit) testl %ebx, %ebx /* swapgs needed? */ jnz .Lparanoid_exit_no_swapgs TRACE_IRQS_IRETQ - RESTORE_CR3 save_reg=%r14 + RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 SWAPGS_UNSAFE_STACK jmp .Lparanoid_exit_restore .Lparanoid_exit_no_swapgs: @@ -1730,7 +1730,7 @@ end_repeat_nmi: movq $-1, %rsi call do_nmi - RESTORE_CR3 save_reg=%r14 + RESTORE_CR3 scratch_reg=%r15 save_reg=%r14 testl %ebx, %ebx /* swapgs needed? */ jnz nmi_restore |