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Date: Fri, 30 Sep 2016 03:45:40 -0700
From: tip-bot for Andy Lutomirski <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: mingo@...nel.org, tglx@...utronix.de, hpa@...or.com,
linux-kernel@...r.kernel.org, bp@...en8.de, brgerst@...il.com,
luto@...nel.org
Subject: [tip:x86/asm] x86/asm: Get rid of __read_cr4_safe()
Commit-ID: 1ef55be16ed69538f89e0a6508be5e62fdc9851c
Gitweb: http://git.kernel.org/tip/1ef55be16ed69538f89e0a6508be5e62fdc9851c
Author: Andy Lutomirski <luto@...nel.org>
AuthorDate: Thu, 29 Sep 2016 12:48:12 -0700
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 30 Sep 2016 12:40:12 +0200
x86/asm: Get rid of __read_cr4_safe()
We use __read_cr4() vs __read_cr4_safe() inconsistently. On
CR4-less CPUs, all CR4 bits are effectively clear, so we can make
the code simpler and more robust by making __read_cr4() always fix
up faults on 32-bit kernels.
This may fix some bugs on old 486-like CPUs, but I don't have any
easy way to test that.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: david@...giorato.net
Link: http://lkml.kernel.org/r/ea647033d357d9ce2ad2bbde5a631045f5052fb6.1475178370.git.luto@kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
arch/x86/include/asm/paravirt.h | 4 ----
arch/x86/include/asm/paravirt_types.h | 1 -
arch/x86/include/asm/special_insns.h | 22 +++++++---------------
arch/x86/include/asm/tlbflush.h | 2 +-
arch/x86/kernel/paravirt.c | 1 -
arch/x86/kernel/process_32.c | 2 +-
arch/x86/kernel/setup.c | 2 +-
arch/x86/power/cpu.c | 2 +-
arch/x86/xen/enlighten.c | 1 -
9 files changed, 11 insertions(+), 26 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 2970d22..91b6f4e 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -80,10 +80,6 @@ static inline unsigned long __read_cr4(void)
{
return PVOP_CALL0(unsigned long, pv_cpu_ops.read_cr4);
}
-static inline unsigned long __read_cr4_safe(void)
-{
- return PVOP_CALL0(unsigned long, pv_cpu_ops.read_cr4_safe);
-}
static inline void __write_cr4(unsigned long x)
{
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 7fa9e77..fcf243f 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -108,7 +108,6 @@ struct pv_cpu_ops {
unsigned long (*read_cr0)(void);
void (*write_cr0)(unsigned long);
- unsigned long (*read_cr4_safe)(void);
unsigned long (*read_cr4)(void);
void (*write_cr4)(unsigned long);
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 587d791..19a2224 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -59,22 +59,19 @@ static inline void native_write_cr3(unsigned long val)
static inline unsigned long native_read_cr4(void)
{
unsigned long val;
- asm volatile("mov %%cr4,%0\n\t" : "=r" (val), "=m" (__force_order));
- return val;
-}
-
-static inline unsigned long native_read_cr4_safe(void)
-{
- unsigned long val;
- /* This could fault if %cr4 does not exist. In x86_64, a cr4 always
- * exists, so it will never fail. */
#ifdef CONFIG_X86_32
+ /*
+ * This could fault if CR4 does not exist. Non-existent CR4
+ * is functionally equivalent to CR4 == 0. Keep it simple and pretend
+ * that CR4 == 0 on CPUs that don't have CR4.
+ */
asm volatile("1: mov %%cr4, %0\n"
"2:\n"
_ASM_EXTABLE(1b, 2b)
: "=r" (val), "=m" (__force_order) : "0" (0));
#else
- val = native_read_cr4();
+ /* CR4 always exists on x86_64. */
+ asm volatile("mov %%cr4,%0\n\t" : "=r" (val), "=m" (__force_order));
#endif
return val;
}
@@ -182,11 +179,6 @@ static inline unsigned long __read_cr4(void)
return native_read_cr4();
}
-static inline unsigned long __read_cr4_safe(void)
-{
- return native_read_cr4_safe();
-}
-
static inline void __write_cr4(unsigned long x)
{
native_write_cr4(x);
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index dee8a70..6fa8594 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -81,7 +81,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate);
/* Initialize cr4 shadow for this CPU. */
static inline void cr4_init_shadow(void)
{
- this_cpu_write(cpu_tlbstate.cr4, __read_cr4_safe());
+ this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
}
/* Set in this cpu's CR4. */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index bef3400..bbf3d59 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -332,7 +332,6 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
.read_cr0 = native_read_cr0,
.write_cr0 = native_write_cr0,
.read_cr4 = native_read_cr4,
- .read_cr4_safe = native_read_cr4_safe,
.write_cr4 = native_write_cr4,
#ifdef CONFIG_X86_64
.read_cr8 = native_read_cr8,
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 404efdf..bd7be8e 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -90,7 +90,7 @@ void __show_regs(struct pt_regs *regs, int all)
cr0 = read_cr0();
cr2 = read_cr2();
cr3 = read_cr3();
- cr4 = __read_cr4_safe();
+ cr4 = __read_cr4();
printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
cr0, cr2, cr3, cr4);
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 87f2330..3aabfdc 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1137,7 +1137,7 @@ void __init setup_arch(char **cmdline_p)
* auditing all the early-boot CR4 manipulation would be needed to
* rule it out.
*/
- mmu_cr4_features = __read_cr4_safe();
+ mmu_cr4_features = __read_cr4();
memblock_set_current_limit(get_max_mapped());
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index b12c26e..53cace2 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -130,7 +130,7 @@ static void __save_processor_state(struct saved_context *ctxt)
ctxt->cr0 = read_cr0();
ctxt->cr2 = read_cr2();
ctxt->cr3 = read_cr3();
- ctxt->cr4 = __read_cr4_safe();
+ ctxt->cr4 = __read_cr4();
#ifdef CONFIG_X86_64
ctxt->cr8 = read_cr8();
#endif
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b86ebb1..e2cf8fc 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1237,7 +1237,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
.write_cr0 = xen_write_cr0,
.read_cr4 = native_read_cr4,
- .read_cr4_safe = native_read_cr4_safe,
.write_cr4 = xen_write_cr4,
#ifdef CONFIG_X86_64
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