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Subject[PATCH 4.9 23/39] kaiser: x86_cr3_pcid_noflush and x86_cr3_pcid_user
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hugh Dickins <hughd@google.com>


Mostly this commit is just unshouting X86_CR3_PCID_KERN_VAR and
X86_CR3_PCID_USER_VAR: we usually name variables in lower-case.

But why does x86_cr3_pcid_noflush need to be __aligned(PAGE_SIZE)?
Ah, it's a leftover from when kaiser_add_user_map() once complained
about mapping the same page twice. Make it __read_mostly instead.
(I'm a little uneasy about all the unrelated data which shares its
page getting user-mapped too, but that was so before, and not a big
deal: though we call it user-mapped, it's not mapped with _PAGE_USER.)

And there is a little change around the two calls to do_nmi().
Previously they set the NOFLUSH bit (if PCID supported) when
forcing to kernel context before do_nmi(); now they also have the
NOFLUSH bit set (if PCID supported) when restoring context after:
nothing done in do_nmi() should require a TLB to be flushed here.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/entry/entry_64.S | 8 ++++----
arch/x86/include/asm/kaiser.h | 11 +++++------
arch/x86/mm/kaiser.c | 13 +++++++------
3 files changed, 16 insertions(+), 16 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1316,11 +1316,11 @@ ENTRY(nmi)
/* Unconditionally use kernel CR3 for do_nmi() */
/* %rax is saved above, so OK to clobber here */
movq %cr3, %rax
+ /* If PCID enabled, NOFLUSH now and NOFLUSH on return */
+ orq x86_cr3_pcid_noflush, %rax
pushq %rax
/* mask off "user" bit of pgd address and 12 PCID bits: */
andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax
- /* Add back kernel PCID and "no flush" bit */
- orq X86_CR3_PCID_KERN_VAR, %rax
movq %rax, %cr3
#endif
call do_nmi
@@ -1560,11 +1560,11 @@ end_repeat_nmi:
/* Unconditionally use kernel CR3 for do_nmi() */
/* %rax is saved above, so OK to clobber here */
movq %cr3, %rax
+ /* If PCID enabled, NOFLUSH now and NOFLUSH on return */
+ orq x86_cr3_pcid_noflush, %rax
pushq %rax
/* mask off "user" bit of pgd address and 12 PCID bits: */
andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax
- /* Add back kernel PCID and "no flush" bit */
- orq X86_CR3_PCID_KERN_VAR, %rax
movq %rax, %cr3
#endif

--- a/arch/x86/include/asm/kaiser.h
+++ b/arch/x86/include/asm/kaiser.h
@@ -25,7 +25,7 @@
.macro _SWITCH_TO_KERNEL_CR3 reg
movq %cr3, \reg
andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg
-orq X86_CR3_PCID_KERN_VAR, \reg
+orq x86_cr3_pcid_noflush, \reg
movq \reg, %cr3
.endm

@@ -37,11 +37,10 @@ movq \reg, %cr3
* not enabled): so that the one register can update both memory and cr3.
*/
movq %cr3, \reg
-andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg
-orq PER_CPU_VAR(X86_CR3_PCID_USER_VAR), \reg
+orq PER_CPU_VAR(x86_cr3_pcid_user), \reg
js 9f
/* FLUSH this time, reset to NOFLUSH for next time (if PCID enabled) */
-movb \regb, PER_CPU_VAR(X86_CR3_PCID_USER_VAR+7)
+movb \regb, PER_CPU_VAR(x86_cr3_pcid_user+7)
9:
movq \reg, %cr3
.endm
@@ -94,8 +93,8 @@ 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_KERN_VAR;
-DECLARE_PER_CPU(unsigned long, X86_CR3_PCID_USER_VAR);
+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
@@ -28,8 +28,8 @@ 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.
*/
-__aligned(PAGE_SIZE) unsigned long X86_CR3_PCID_KERN_VAR;
-DEFINE_PER_CPU(unsigned long, X86_CR3_PCID_USER_VAR);
+unsigned long x86_cr3_pcid_noflush __read_mostly;
+DEFINE_PER_CPU(unsigned long, x86_cr3_pcid_user);

/*
* At runtime, the only things we map are some things for CPU
@@ -303,7 +303,8 @@ void __init kaiser_init(void)
sizeof(gate_desc) * NR_VECTORS,
__PAGE_KERNEL);

- kaiser_add_user_map_early(&X86_CR3_PCID_KERN_VAR, PAGE_SIZE,
+ kaiser_add_user_map_early(&x86_cr3_pcid_noflush,
+ sizeof(x86_cr3_pcid_noflush),
__PAGE_KERNEL);
}

@@ -381,8 +382,8 @@ void kaiser_setup_pcid(void)
* These variables are used by the entry/exit
* code to change PCID and pgd and TLB flushing.
*/
- X86_CR3_PCID_KERN_VAR = kern_cr3;
- this_cpu_write(X86_CR3_PCID_USER_VAR, user_cr3);
+ x86_cr3_pcid_noflush = kern_cr3;
+ this_cpu_write(x86_cr3_pcid_user, user_cr3);
}

/*
@@ -392,7 +393,7 @@ void kaiser_setup_pcid(void)
*/
void kaiser_flush_tlb_on_return_to_user(void)
{
- this_cpu_write(X86_CR3_PCID_USER_VAR,
+ this_cpu_write(x86_cr3_pcid_user,
X86_CR3_PCID_USER_FLUSH | KAISER_SHADOW_PGD_OFFSET);
}
EXPORT_SYMBOL(kaiser_flush_tlb_on_return_to_user);

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