This is a note to let you know that I've just added the patch titled

kaiser: use ALTERNATIVE instead of x86_cr3_pcid_noflush

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kaiser-use-alternative-instead-of-x86_cr3_pcid_noflush.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Jan 3 20:37:21 CET 2018

From: Hugh Dickins hughd@google.com Date: Tue, 3 Oct 2017 20:49:04 -0700 Subject: kaiser: use ALTERNATIVE instead of x86_cr3_pcid_noflush

From: Hugh Dickins hughd@google.com

Now that we're playing the ALTERNATIVE game, use that more efficient method: instead of user-mapping an extra page, and reading an extra cacheline each time for x86_cr3_pcid_noflush.

Neel has found that __stringify(bts $X86_CR3_PCID_NOFLUSH_BIT, %rax) is a working substitute for the "bts $63, %rax" in these ALTERNATIVEs; but the one line with $63 in looks clearer, so let's stick with that.

Worried about what happens with an ALTERNATIVE between the jump and jump label in another ALTERNATIVE? I was, but have checked the combinations in SWITCH_KERNEL_CR3_NO_STACK at entry_SYSCALL_64, and it does a good job.

Signed-off-by: Hugh Dickins hughd@google.com Acked-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/entry/entry_64.S | 7 ++++--- arch/x86/include/asm/kaiser.h | 6 +++--- arch/x86/mm/kaiser.c | 11 +---------- 3 files changed, 8 insertions(+), 16 deletions(-)

--- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1084,7 +1084,8 @@ ENTRY(paranoid_entry) jz 2f orl $2, %ebx andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax - orq x86_cr3_pcid_noflush, %rax + /* If PCID enabled, set X86_CR3_PCID_NOFLUSH_BIT */ + ALTERNATIVE "", "bts $63, %rax", X86_FEATURE_PCID movq %rax, %cr3 2: #endif @@ -1344,7 +1345,7 @@ ENTRY(nmi) /* %rax is saved above, so OK to clobber here */ ALTERNATIVE "jmp 2f", "movq %cr3, %rax", X86_FEATURE_KAISER /* If PCID enabled, NOFLUSH now and NOFLUSH on return */ - orq x86_cr3_pcid_noflush, %rax + ALTERNATIVE "", "bts $63, %rax", X86_FEATURE_PCID pushq %rax /* mask off "user" bit of pgd address and 12 PCID bits: */ andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax @@ -1588,7 +1589,7 @@ end_repeat_nmi: /* %rax is saved above, so OK to clobber here */ ALTERNATIVE "jmp 2f", "movq %cr3, %rax", X86_FEATURE_KAISER /* If PCID enabled, NOFLUSH now and NOFLUSH on return */ - orq x86_cr3_pcid_noflush, %rax + ALTERNATIVE "", "bts $63, %rax", X86_FEATURE_PCID pushq %rax /* mask off "user" bit of pgd address and 12 PCID bits: */ andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax --- a/arch/x86/include/asm/kaiser.h +++ b/arch/x86/include/asm/kaiser.h @@ -25,7 +25,8 @@ .macro _SWITCH_TO_KERNEL_CR3 reg movq %cr3, \reg andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg -orq x86_cr3_pcid_noflush, \reg +/* If PCID enabled, set X86_CR3_PCID_NOFLUSH_BIT */ +ALTERNATIVE "", "bts $63, \reg", X86_FEATURE_PCID movq \reg, %cr3 .endm

@@ -39,7 +40,7 @@ movq \reg, %cr3 movq %cr3, \reg orq PER_CPU_VAR(x86_cr3_pcid_user), \reg js 9f -/* FLUSH this time, reset to NOFLUSH for next time (if PCID enabled) */ +/* If PCID enabled, FLUSH this time, reset to NOFLUSH for next time */ movb \regb, PER_CPU_VAR(x86_cr3_pcid_user+7) 9: movq \reg, %cr3 @@ -90,7 +91,6 @@ movq PER_CPU_VAR(unsafe_stack_register_b */ DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);

-extern unsigned long x86_cr3_pcid_noflush; DECLARE_PER_CPU(unsigned long, x86_cr3_pcid_user);

extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[]; --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -31,7 +31,6 @@ DEFINE_PER_CPU_USER_MAPPED(unsigned long * This is also handy because systems that do not support PCIDs * just end up or'ing a 0 into their CR3, which does no harm. */ -unsigned long x86_cr3_pcid_noflush __read_mostly; DEFINE_PER_CPU(unsigned long, x86_cr3_pcid_user);

/* @@ -356,10 +355,6 @@ void __init kaiser_init(void) kaiser_add_user_map_early(&debug_idt_table, sizeof(gate_desc) * NR_VECTORS, __PAGE_KERNEL); - - kaiser_add_user_map_early(&x86_cr3_pcid_noflush, - sizeof(x86_cr3_pcid_noflush), - __PAGE_KERNEL); }

/* Add a mapping to the shadow mapping, and synchronize the mappings */ @@ -433,18 +428,14 @@ pgd_t kaiser_set_shadow_pgd(pgd_t *pgdp,

void kaiser_setup_pcid(void) { - unsigned long kern_cr3 = 0; unsigned long user_cr3 = KAISER_SHADOW_PGD_OFFSET;

- if (this_cpu_has(X86_FEATURE_PCID)) { - kern_cr3 |= X86_CR3_PCID_KERN_NOFLUSH; + if (this_cpu_has(X86_FEATURE_PCID)) user_cr3 |= X86_CR3_PCID_USER_NOFLUSH; - } /* * These variables are used by the entry/exit * code to change PCID and pgd and TLB flushing. */ - x86_cr3_pcid_noflush = kern_cr3; this_cpu_write(x86_cr3_pcid_user, user_cr3); }

Patches currently in stable-queue which might be from hughd@google.com are

queue-4.9/kaiser-vmstat-show-nr_kaisertable-as-nr_overhead.patch queue-4.9/kaiser-add-nokaiser-boot-option-using-alternative.patch queue-4.9/kaiser-fix-unlikely-error-in-alloc_ldt_struct.patch queue-4.9/kaiser-kaiser_flush_tlb_on_return_to_user-check-pcid.patch queue-4.9/x86-paravirt-dont-patch-flush_tlb_single.patch queue-4.9/kaiser-merged-update.patch queue-4.9/kaiser-delete-kaiser_real_switch-option.patch queue-4.9/kaiser-kaiser_remove_mapping-move-along-the-pgd.patch queue-4.9/kaiser-fix-perf-crashes.patch queue-4.9/kaiser-drop-is_atomic-arg-to-kaiser_pagetable_walk.patch queue-4.9/kaiser-load_new_mm_cr3-let-switch_user_cr3-flush-user.patch queue-4.9/kaiser-enhanced-by-kernel-and-user-pcids.patch queue-4.9/kaiser-x86_cr3_pcid_noflush-and-x86_cr3_pcid_user.patch queue-4.9/kaiser-align-addition-to-x86-mm-makefile.patch queue-4.9/kaiser-use-alternative-instead-of-x86_cr3_pcid_noflush.patch queue-4.9/kaiser-stack-map-page_size-at-thread_size-page_size.patch queue-4.9/kaiser-name-that-0x1000-kaiser_shadow_pgd_offset.patch queue-4.9/kaiser-fix-regs-to-do_nmi-ifndef-config_kaiser.patch queue-4.9/kaiser-do-not-set-_page_nx-on-pgd_none.patch queue-4.9/kaiser-tidied-up-asm-kaiser.h-somewhat.patch queue-4.9/kaiser-cleanups-while-trying-for-gold-link.patch queue-4.9/kaiser-tidied-up-kaiser_add-remove_mapping-slightly.patch queue-4.9/kaiser-fix-build-and-fixme-in-alloc_ldt_struct.patch queue-4.9/kaiser-kernel-address-isolation.patch queue-4.9/kaiser-enomem-if-kaiser_pagetable_walk-null.patch queue-4.9/kaiser-asm-tlbflush.h-handle-nopge-at-lower-level.patch queue-4.9/kaiser-paranoid_entry-pass-cr3-need-to-paranoid_exit.patch queue-4.9/kaiser-kaiser-depends-on-smp.patch queue-4.9/kaiser-pcid-0-for-kernel-and-128-for-user.patch