[tip:x86/cpu] x86, msr: Add rd/wrmsr interfaces with preset registers

tip-bot for Borislav Petkov
2009-08-31T23:37:35Z

Commit-ID: 132ec92f3f70fe365c1f4b8d46e66cf8a2a16880
Gitweb: http://git.kernel.org/tip/132ec92f3f70fe365c1f4b8d46e66cf8a2a16880
Author: Borislav Petkov <petkovbb@googlemail.com>
AuthorDate: Mon, 31 Aug 2009 09:50:09 +0200
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Mon, 31 Aug 2009 15:14:26 -0700

x86, msr: Add rd/wrmsr interfaces with preset registers

native_{rdmsr,wrmsr}_safe_regs are two new interfaces which allow
presetting of a subset of eight x86 GPRs before executing the rd/wrmsr
instructions. This is needed at least on AMD K8 for accessing an erratum
workaround MSR.

Originally based on an idea by H. Peter Anvin.

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
LKML-Reference: <1251705011-18636-1-git-send-email-petkovbb@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

---
arch/x86/include/asm/msr.h | 13 +++++
arch/x86/include/asm/paravirt.h | 16 ++++++
arch/x86/kernel/paravirt.c | 2 +
arch/x86/lib/Makefile | 1 +
arch/x86/lib/msr-reg.S | 98 +++++++++++++++++++++++++++++++++++++++
5 files changed, 130 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 48ad9d2..184d4a1 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -113,6 +113,9 @@ notrace static inline int native_write_msr_safe(unsigned int msr,

extern unsigned long long native_read_tsc(void);

+extern int native_rdmsr_safe_regs(u32 *regs);
+extern int native_wrmsr_safe_regs(u32 *regs);
+
static __always_inline unsigned long long __native_read_tsc(void)
{
DECLARE_ARGS(val, low, high);
@@ -189,6 +192,16 @@ static inline int rdmsrl_amd_safe(unsigned msr, unsigned long long *p)
return err;
}

+static inline int rdmsr_safe_regs(u32 *regs)
+{
+ return native_rdmsr_safe_regs(regs);
+}
+
+static inline int wrmsr_safe_regs(u32 *regs)
+{
+ return native_wrmsr_safe_regs(regs);
+}
+
#define rdtscl(low) \
((low) = (u32)__native_read_tsc())

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 4fb37c8..1705944 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -168,7 +168,9 @@ struct pv_cpu_ops {
err = 0/-EFAULT. wrmsr returns 0/-EFAULT. */
u64 (*read_msr_amd)(unsigned int msr, int *err);
u64 (*read_msr)(unsigned int msr, int *err);
+ int (*rdmsr_regs)(u32 *regs);
int (*write_msr)(unsigned int msr, unsigned low, unsigned high);
+ int (*wrmsr_regs)(u32 *regs);

u64 (*read_tsc)(void);
u64 (*read_pmc)(int counter);
@@ -820,6 +822,12 @@ static inline u64 paravirt_read_msr(unsigned msr, int *err)
{
return PVOP_CALL2(u64, pv_cpu_ops.read_msr, msr, err);
}
+
+static inline int paravirt_rdmsr_regs(u32 *regs)
+{
+ return PVOP_CALL1(int, pv_cpu_ops.rdmsr_regs, regs);
+}
+
static inline u64 paravirt_read_msr_amd(unsigned msr, int *err)
{
return PVOP_CALL2(u64, pv_cpu_ops.read_msr_amd, msr, err);
@@ -829,6 +837,11 @@ static inline int paravirt_write_msr(unsigned msr, unsigned low, unsigned high)
return PVOP_CALL3(int, pv_cpu_ops.write_msr, msr, low, high);
}

+static inline int paravirt_wrmsr_regs(u32 *regs)
+{
+ return PVOP_CALL1(int, pv_cpu_ops.wrmsr_regs, regs);
+}
+
/* These should all do BUG_ON(_err), but our headers are too tangled. */
#define rdmsr(msr, val1, val2) \
do { \
@@ -862,6 +875,9 @@ do { \
_err; \
})

+#define rdmsr_safe_regs(regs) paravirt_rdmsr_regs(regs)
+#define wrmsr_safe_regs(regs) paravirt_wrmsr_regs(regs)
+
static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
{
int err;
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 70ec9b9..67594af 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -362,8 +362,10 @@ struct pv_cpu_ops pv_cpu_ops = {
#endif
.wbinvd = native_wbinvd,
.read_msr = native_read_msr_safe,
+ .rdmsr_regs = native_rdmsr_safe_regs,
.read_msr_amd = native_read_msr_amd_safe,
.write_msr = native_write_msr_safe,
+ .wrmsr_regs = native_wrmsr_safe_regs,
.read_tsc = native_read_tsc,
.read_pmc = native_read_pmc,
.read_tscp = native_read_tscp,
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 07c3189..b59c064 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -8,6 +8,7 @@ lib-y := delay.o
lib-y += thunk_$(BITS).o
lib-y += usercopy_$(BITS).o getuser.o putuser.o
lib-y += memcpy_$(BITS).o
+lib-y += msr-reg.o

ifeq ($(CONFIG_X86_32),y)
obj-y += atomic64_32.o
diff --git a/arch/x86/lib/msr-reg.S b/arch/x86/lib/msr-reg.S
new file mode 100644
index 0000000..51f1bb3
--- /dev/null
+++ b/arch/x86/lib/msr-reg.S
@@ -0,0 +1,98 @@
+#include <linux/linkage.h>
+#include <linux/errno.h>
+#include <asm/asm.h>
+#include <asm/msr.h>
+
+#ifdef CONFIG_X86_64
+/*
+ * int native_{rdmsr,wrmsr}_safe_regs(u32 gprs[8]);
+ *
+ * reg layout: u32 gprs[eax, ecx, edx, ebx, esp, ebp, esi, edi]
+ *
+ */
+.macro op_safe_regs op:req
+ENTRY(native_\op\()_safe_regs)
+ push %rbx
+ push %rbp
+ push $0 /* Return value */
+ push %rdi
+ movl (%rdi), %eax
+ movl 4(%rdi), %ecx
+ movl 8(%rdi), %edx
+ movl 12(%rdi), %ebx
+ movl 20(%rdi), %ebp
+ movl 24(%rdi), %esi
+ movl 28(%rdi), %edi
+1: \op
+2: movl %edi, %r10d
+ pop %rdi
+ movl %eax, (%rdi)
+ movl %ecx, 4(%rdi)
+ movl %edx, 8(%rdi)
+ movl %ebx, 12(%rdi)
+ movl %ebp, 20(%rdi)
+ movl %esi, 24(%rdi)
+ movl %r10d, 28(%rdi)
+ pop %rax
+ pop %rbp
+ pop %rbx
+ ret
+3:
+ movq $-EIO, 8(%rsp)
+ jmp 2b
+ .section __ex_table,"ax"
+ .balign 4
+ .quad 1b, 3b
+ .previous
+ENDPROC(native_\op\()_safe_regs)
+.endm
+
+#else /* X86_32 */
+
+.macro op_safe_regs op:req
+ENTRY(native_\op\()_safe_regs)
+ push %ebx
+ push %ebp
+ push %esi
+ push %edi
+ push $0 /* Return value */
+ push %eax
+ movl 4(%eax), %ecx
+ movl 8(%eax), %edx
+ movl 12(%eax), %ebx
+ movl 20(%eax), %ebp
+ movl 24(%eax), %esi
+ movl 28(%eax), %edi
+ movl (%eax), %eax
+1: \op
+2: push %eax
+ movl 4(%esp), %eax
+ pop (%eax)
+ addl $4, %esp
+ movl %ecx, 4(%eax)
+ movl %edx, 8(%eax)
+ movl %ebx, 12(%eax)
+ movl %ebp, 20(%eax)
+ movl %esi, 24(%eax)
+ movl %edi, 28(%eax)
+ pop %eax
+ pop %edi
+ pop %esi
+ pop %ebp
+ pop %ebx
+ ret
+3:
+ movl $-EIO, 4(%esp)
+ jmp 2b
+ .section __ex_table,"ax"
+ .balign 4
+ .long 1b, 3b
+ .previous
+ENDPROC(native_\op\()_safe_regs)
+.endm
+
+#endif
+
+op_safe_regs rdmsr
+op_safe_regs wrmsr
+