[Xen-devel] [V2] x86/xsaves: calculate the xstate_comp_offsets base on xcomp_bv

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

Previous patch using all available features calculate xstate_comp_offsets.
This is wrong.This patch fix this bug by calculating the xstate_comp_offset
based on xcomp_bv of current guest.
Also, the xstate_comp_offset should take alignment into consideration.

V2: Address comments from Jan:
 1. code style fix
 2. setup_xstate_comp take xcomp_bv as param.

Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>
Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/xstate.c        | 34 ++++++++++++++++++++++++----------
 xen/include/asm-x86/xstate.h |  2 ++
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index 8316bd9..dd6d37a 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -26,6 +26,7 @@ u64 __read_mostly xfeature_mask;
 
 static unsigned int *__read_mostly xstate_offsets;
 unsigned int *__read_mostly xstate_sizes;
+static unsigned int *__read_mostly xstate_align;
 static unsigned int __read_mostly xstate_features;
 static unsigned int __read_mostly xstate_comp_offsets[sizeof(xfeature_mask)*8];
 
@@ -94,7 +95,7 @@ static bool_t xsave_area_compressed(const struct xsave_struct 
*xsave_area)
 
 static int setup_xstate_features(bool_t bsp)
 {
-    unsigned int leaf, tmp, eax, ebx;
+    unsigned int leaf, eax, ebx, ecx, edx;
 
     if ( bsp )
     {
@@ -106,26 +107,34 @@ static int setup_xstate_features(bool_t bsp)
         xstate_sizes = xzalloc_array(unsigned int, xstate_features);
         if ( !xstate_sizes )
             return -ENOMEM;
+
+        xstate_align = xzalloc_array(unsigned int, xstate_features);
+        if ( !xstate_align )
+            return -ENOMEM;
     }
 
     for ( leaf = 2; leaf < xstate_features; leaf++ )
     {
         if ( bsp )
+        {
             cpuid_count(XSTATE_CPUID, leaf, &xstate_sizes[leaf],
-                        &xstate_offsets[leaf], &tmp, &tmp);
+                        &xstate_offsets[leaf], &ecx, &edx);
+            xstate_align[leaf] = ecx & XSTATE_ALIGN64;
+        }
         else
         {
             cpuid_count(XSTATE_CPUID, leaf, &eax,
-                        &ebx, &tmp, &tmp);
+                        &ebx, &ecx, &edx);
             BUG_ON(eax != xstate_sizes[leaf]);
             BUG_ON(ebx != xstate_offsets[leaf]);
+            BUG_ON((ecx & XSTATE_ALIGN64) != xstate_align[leaf]);
         }
     }
 
     return 0;
 }
 
-static void __init setup_xstate_comp(void)
+static void setup_xstate_comp(const u64 xcomp_bv)
 {
     unsigned int i;
 
@@ -134,16 +143,19 @@ static void __init setup_xstate_comp(void)
      * in the fixed offsets in the xsave area in either compacted form
      * or standard form.
      */
-    xstate_comp_offsets[0] = 0;
+    memset(xstate_comp_offsets, 0, sizeof(xstate_comp_offsets));
+
     xstate_comp_offsets[1] = XSAVE_SSE_OFFSET;
 
     xstate_comp_offsets[2] = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 
     for ( i = 3; i < xstate_features; i++ )
     {
-        xstate_comp_offsets[i] = xstate_comp_offsets[i - 1] +
-                                 (((1ul << i) & xfeature_mask)
-                                  ? xstate_sizes[i - 1] : 0);
+        xstate_comp_offsets[i] = (xstate_align[i] ?
+                                 ROUNDUP(xstate_comp_offsets[i-1], 64) :
+                                 xstate_comp_offsets[i - 1]) +
+                                 (((1ul << i) & xcomp_bv)
+                                 ? xstate_sizes[i - 1] : 0);
         ASSERT(xstate_comp_offsets[i] + xstate_sizes[i] <= xsave_cntxt_size);
     }
 }
@@ -172,6 +184,8 @@ void expand_xsave_states(struct vcpu *v, void *dest, 
unsigned int size)
     }
 
     ASSERT(xsave_area_compressed(xsave));
+    setup_xstate_comp(xsave->xsave_hdr.xcomp_bv);
+
     /*
      * Copy legacy XSAVE area and XSAVE hdr area.
      */
@@ -223,6 +237,8 @@ void compress_xsave_states(struct vcpu *v, const void *src, 
unsigned int size)
     xsave->xsave_hdr.xstate_bv = xstate_bv;
     xsave->xsave_hdr.xcomp_bv = v->arch.xcr0_accum | XSTATE_COMPACTION_ENABLED;
 
+    setup_xstate_comp(xsave->xsave_hdr.xcomp_bv);
+
     /*
      * Copy each region from the non-compacted offset to the
      * possibly compacted offset.
@@ -575,8 +591,6 @@ void xstate_init(struct cpuinfo_x86 *c)
 
     if ( setup_xstate_features(bsp) && bsp )
         BUG();
-    if ( bsp && (cpu_has_xsaves || cpu_has_xsavec) )
-        setup_xstate_comp();
 }
 
 static bool_t valid_xcr0(u64 xcr0)
diff --git a/xen/include/asm-x86/xstate.h b/xen/include/asm-x86/xstate.h
index c28cea5..61d1ddb 100644
--- a/xen/include/asm-x86/xstate.h
+++ b/xen/include/asm-x86/xstate.h
@@ -46,6 +46,8 @@
 #define XSTATE_LAZY    (XSTATE_ALL & ~XSTATE_NONLAZY)
 #define XSTATE_COMPACTION_ENABLED  (1ULL << 63)
 
+#define XSTATE_ALIGN64 (1ULL << 1)
+
 extern u64 xfeature_mask;
 extern unsigned int *xstate_sizes;
 
-- 
1.9.1


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