[PATCH 8/8] x86, xsave: add kernel support for AMDs Lightweight Profiling (LWP)

Hans Rosenfeld
2011-12-07T20:02:53Z

This patch extends the xsave structure to support the LWP state. The
xstate feature bit for LWP is added to XCNTXT_NONLAZY, thereby enabling
kernel support for saving/restoring LWP state. The LWP state is also
saved/restored on signal entry/return, just like all other xstates. LWP
state needs to be reset (disabled) when entering a signal handler.

v2:
When copying xstates for fork/clone, disable LWP in the new copy so that
new tasks start with LWP disabled as required by the LWP specification.

Signed-off-by: Hans Rosenfeld <hans.rosenfeld@amd.com>
---
arch/x86/include/asm/i387.h | 4 ++++
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/include/asm/processor.h | 12 ++++++++++++
arch/x86/include/asm/sigcontext.h | 12 ++++++++++++
arch/x86/include/asm/xsave.h | 3 ++-
arch/x86/kernel/xsave.c | 5 +++++
6 files changed, 36 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 7812d55..cfd0be9 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -326,6 +326,10 @@ static inline void fpu_free(struct fpu *fpu)
static inline void fpu_copy(struct fpu *dst, struct fpu *src)
{
memcpy(dst->state, src->state, xstate_size);
+
+ /* disable LWP in the copy */
+ if (pcntxt_mask & XSTATE_LWP)
+ dst->state->xsave.xsave_hdr.xstate_bv &= ~XSTATE_LWP;
}

extern void fpu_finit(struct fpu *fpu);
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index d52609a..2d9cf3c 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -136,6 +136,7 @@
#define MSR_AMD64_IBSDCPHYSAD 0xc0011039
#define MSR_AMD64_IBSCTL 0xc001103a
#define MSR_AMD64_IBSBRTARGET 0xc001103b
+#define MSR_AMD64_LWP_CBADDR 0xc0000106

/* Fam 15h MSRs */
#define MSR_F15H_PERF_CTL 0xc0010200
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0d1171c..bb31ab6 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -353,6 +353,17 @@ struct ymmh_struct {
u32 ymmh_space[64];
};

+struct lwp_struct {
+ u64 lwpcb_addr;
+ u32 flags;
+ u32 buf_head_offset;
+ u64 buf_base;
+ u32 buf_size;
+ u32 filters;
+ u64 saved_event_record[4];
+ u32 event_counter[16];
+};
+
struct xsave_hdr_struct {
u64 xstate_bv;
u64 reserved1[2];
@@ -363,6 +374,7 @@ struct xsave_struct {
struct i387_fxsave_struct i387;
struct xsave_hdr_struct xsave_hdr;
struct ymmh_struct ymmh;
+ struct lwp_struct lwp;
/* new processor state extensions will go here */
} __attribute__ ((packed, aligned (64)));

diff --git a/arch/x86/include/asm/sigcontext.h b/arch/x86/include/asm/sigcontext.h
index 04459d2..0a58b82 100644
--- a/arch/x86/include/asm/sigcontext.h
+++ b/arch/x86/include/asm/sigcontext.h
@@ -274,6 +274,17 @@ struct _ymmh_state {
__u32 ymmh_space[64];
};

+struct _lwp_state {
+ __u64 lwpcb_addr;
+ __u32 flags;
+ __u32 buf_head_offset;
+ __u64 buf_base;
+ __u32 buf_size;
+ __u32 filters;
+ __u64 saved_event_record[4];
+ __u32 event_counter[16];
+};
+
/*
* Extended state pointed by the fpstate pointer in the sigcontext.
* In addition to the fpstate, information encoded in the xstate_hdr
@@ -284,6 +295,7 @@ struct _xstate {
struct _fpstate fpstate;
struct _xsave_hdr xstate_hdr;
struct _ymmh_state ymmh;
+ struct _lwp_state lwp;
/* new processor state extensions go here */
};

diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index 10e0e45..789a140 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -9,6 +9,7 @@
#define XSTATE_FP 0x1
#define XSTATE_SSE 0x2
#define XSTATE_YMM 0x4
+#define XSTATE_LWP (1ULL << 62)

#define XSTATE_FPSSE (XSTATE_FP | XSTATE_SSE)

@@ -24,7 +25,7 @@
* These are the features that the OS can handle currently.
*/
#define XCNTXT_LAZY (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
-#define XCNTXT_NONLAZY 0
+#define XCNTXT_NONLAZY (XSTATE_LWP)

#ifdef CONFIG_NONLAZY_XSTATES
#define XCNTXT_MASK (XCNTXT_LAZY | XCNTXT_NONLAZY)
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index ce329ff..2022069 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -249,6 +249,11 @@ int save_xstates_sigframe(void __user *buf, unsigned int size)
return err;
}

+ if (pcntxt_mask & XSTATE_LWP) {
+ xsave->xsave_hdr.xstate_bv &= ~XSTATE_LWP;
+ wrmsrl(MSR_AMD64_LWP_CBADDR, 0);
+ }
+
return 1;
}

--
1.7.5.4