[PATCH 4/5][RFC] lwp: adding support for AMD lightweight profiling

[Wei Huang <wei.huang2@amd.com>]

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Add xsave/xrstor support for LWP

Because LWP is not tracked by TS, which is used in current xsave/xrstor 
implementation for FPU/AVX. As a result, we have to save and restore LWP 
in extended area whenever vcpu is re-scheduled. To avoid unnecessary lwp 
save/restore, this patch checks the LWP_CBADDR to determine whether LWP 
has been turned on.

Signed-off-by: Wei Huang <wei.huang2@amd.com>




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exporting patch:
# HG changeset patch
# User Wei Huang <wei.huang2@amd.com>
# Date 1297378527 21600
# Node ID 1a1d593c16f36e9cf0153b2ca90dddae649a52bd
# Parent  705de1dacabeb899fae6e8121483b2d88d120e57
Add xsave/xrstor support for LWP

Because LWP is not tracked by TS, which is used in current xsave/xrstor implementation for FPU/AVX. As a result, we have to save and restore LWP in extended area whenever vcpu is re-scheduled. To avoid unnecessary lwp save/restore, this patch checks the LWP_CBADDR to determine whether LWP has been turned on.

diff -r 705de1dacabe -r 1a1d593c16f3 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c	Thu Feb 10 16:25:09 2011 -0600
+++ b/xen/arch/x86/domain.c	Thu Feb 10 16:55:27 2011 -0600
@@ -1385,6 +1385,7 @@
                stack_regs,
                CTXT_SWITCH_STACK_BYTES);
         save_init_fpu(p);
+        xsave_lwp(p);
         p->arch.ctxt_switch_from(p);
     }
 
@@ -1404,6 +1405,7 @@
                CTXT_SWITCH_STACK_BYTES);
         if ( cpu_has_xsave && n->arch.xcr0 != get_xcr0() )
             set_xcr0(n->arch.xcr0);
+        xrstor_lwp(n);
         n->arch.ctxt_switch_to(n);
     }
 
diff -r 705de1dacabe -r 1a1d593c16f3 xen/arch/x86/i387.c
--- a/xen/arch/x86/i387.c	Thu Feb 10 16:25:09 2011 -0600
+++ b/xen/arch/x86/i387.c	Thu Feb 10 16:55:27 2011 -0600
@@ -65,6 +65,55 @@
 static void init_fpu(void);
 static void restore_fpu(struct vcpu *v);
 
+/* Save AMD LWP */
+void xsave_lwp(struct vcpu *v)
+{
+    uint64_t lwpcb;
+    bool_t ts;
+    struct xsave_struct *xsave_area = v->arch.xsave_area;
+
+    if ( cpu_has_lwp )
+    {
+        /* Has LWP been used? */
+        rdmsrl(MSR_AMD_LWP_CBADDR, lwpcb);
+        if ( !lwpcb ) {
+            /* Guest might have turned off LWP. So clean the bit here. */
+            xsave_area->xsave_hdr.xstate_bv &= ~XSTATE_LWP;
+            return;
+        }
+        
+        /* Disable TS temporarily to avoid recursion. */
+        ts = read_cr0() & X86_CR0_TS;
+        clts();
+        xsave(v, XSTATE_LWP);
+        if ( ts )
+            stts();
+
+        /* disable LWP for next VCPU */
+        wrmsrl(MSR_AMD_LWP_CBADDR, 0);
+    }
+}
+
+void xrstor_lwp(struct vcpu *v)
+{
+    bool_t ts;
+    struct xsave_struct *xsave_area = v->arch.xsave_area;
+
+    if ( cpu_has_lwp )
+    {
+        /* Don't do anything if there is no LWP state for this VCPU */
+        if ( !(xsave_area->xsave_hdr.xstate_bv & XSTATE_LWP) )
+            return;
+
+        /* Disable TS temporarily to avoid recursion. */
+        ts = read_cr0() & X86_CR0_TS;
+        clts();
+        xrstor(v, XSTATE_LWP);
+        if ( ts )
+            stts();
+    }
+}
+
 void setup_fpu(struct vcpu *v)
 {
     ASSERT(!is_idle_vcpu(v));
diff -r 705de1dacabe -r 1a1d593c16f3 xen/include/asm-x86/i387.h
--- a/xen/include/asm-x86/i387.h	Thu Feb 10 16:25:09 2011 -0600
+++ b/xen/include/asm-x86/i387.h	Thu Feb 10 16:55:27 2011 -0600
@@ -20,6 +20,8 @@
 void xsave_init(void);
 int xsave_alloc_save_area(struct vcpu *v);
 void xsave_free_save_area(struct vcpu *v);
+void xsave_lwp(struct vcpu *v);
+void xrstor_lwp(struct vcpu *v);
 
 #define XSAVE_AREA_MIN_SIZE (512 + 64) /* FP/SSE + XSAVE.HEADER */
 #define XSTATE_FP       (1ULL << 0)
@@ -33,7 +35,7 @@
 #define XSAVEOPT        (1 << 0)
 
 /* The features that the OS saves/restores by default. */
-#define XCNTXT_DEFAULT     (-1)
+#define XCNTXT_DEFAULT     (~XSTATE_LWP)
 
 struct xsave_struct
 {

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