[Xen-changelog] [xen staging] x86: consolidate legacy FPU state loading

[patchbot@xxxxxxx]

commit 0339b7704d1710cc31238bf91da0bee8af13f837
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Jul 9 10:52:50 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jul 9 10:52:50 2018 +0200

    x86: consolidate legacy FPU state loading
    
    First of all introduce a helper function instead of replicating almost
    the same code for PV and HVM. The differences between the two pieces of
    code actually points out an issue (which is also addressed here): In
    the HVM case FCW would not have been set to FCW_RESET in certain cases
    (note for example that XRSTOR loads FCW_DEFAULT rather then FCW_RESET
    when the respective xstate_bv bit is clear).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/domain.c      | 26 +++-----------------------
 xen/arch/x86/hvm/hvm.c     | 30 +++++-------------------------
 xen/arch/x86/i387.c        | 43 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/i387.h |  3 +++
 4 files changed, 54 insertions(+), 48 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 6201dffb9a..5c10401654 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -834,35 +834,15 @@ int arch_set_info_guest(
             return -EINVAL;
     }
 
-    v->fpu_initialised = !!(flags & VGCF_I387_VALID);
-
     v->arch.flags &= ~TF_kernel_mode;
     if ( (flags & VGCF_in_kernel) || is_hvm_domain(d)/*???*/ )
         v->arch.flags |= TF_kernel_mode;
 
     v->arch.vgc_flags = flags;
 
-    if ( flags & VGCF_I387_VALID )
-    {
-        memcpy(v->arch.fpu_ctxt, &c.nat->fpu_ctxt, sizeof(c.nat->fpu_ctxt));
-        if ( v->arch.xsave_area )
-            v->arch.xsave_area->xsave_hdr.xstate_bv = XSTATE_FP_SSE;
-    }
-    else if ( v->arch.xsave_area )
-    {
-        v->arch.xsave_area->xsave_hdr.xstate_bv = 0;
-        v->arch.xsave_area->fpu_sse.mxcsr = MXCSR_DEFAULT;
-    }
-    else
-    {
-        typeof(v->arch.xsave_area->fpu_sse) *fpu_sse = v->arch.fpu_ctxt;
-
-        memset(fpu_sse, 0, sizeof(*fpu_sse));
-        fpu_sse->fcw = FCW_DEFAULT;
-        fpu_sse->mxcsr = MXCSR_DEFAULT;
-    }
-    if ( v->arch.xsave_area )
-        v->arch.xsave_area->xsave_hdr.xcomp_bv = 0;
+    vcpu_setup_fpu(v, v->arch.xsave_area,
+                   flags & VGCF_I387_VALID ? &c.nat->fpu_ctxt : NULL,
+                   FCW_DEFAULT);
 
     if ( !compat )
     {
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 279cb88e45..6a123a2a6f 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -981,7 +981,6 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
     struct hvm_hw_cpu ctxt;
     struct segment_register seg;
     const char *errstr;
-    struct xsave_struct *xsave_area;
 
     /* Which vcpu is this? */
     vcpuid = hvm_load_instance(h);
@@ -1114,22 +1113,9 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
     hvm_set_segment_register(v, x86_seg_ldtr, &seg);
 
     /* Cover xsave-absent save file restoration on xsave-capable host. */
-    xsave_area = xsave_enabled(v) ? NULL : v->arch.xsave_area;
-
-    v->fpu_initialised = !!(ctxt.flags & XEN_X86_FPU_INITIALISED);
-    if ( v->fpu_initialised )
-    {
-        memcpy(v->arch.fpu_ctxt, ctxt.fpu_regs, sizeof(ctxt.fpu_regs));
-        if ( xsave_area )
-            xsave_area->xsave_hdr.xstate_bv = XSTATE_FP_SSE;
-    }
-    else if ( xsave_area )
-    {
-        xsave_area->xsave_hdr.xstate_bv = 0;
-        xsave_area->fpu_sse.mxcsr = MXCSR_DEFAULT;
-    }
-    if ( xsave_area )
-        xsave_area->xsave_hdr.xcomp_bv = 0;
+    vcpu_setup_fpu(v, xsave_enabled(v) ? NULL : v->arch.xsave_area,
+                   ctxt.flags & XEN_X86_FPU_INITIALISED ? ctxt.fpu_regs : NULL,
+                   FCW_RESET);
 
     v->arch.user_regs.rax = ctxt.rax;
     v->arch.user_regs.rbx = ctxt.rbx;
@@ -3878,7 +3864,6 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
uint16_t ip)
 {
     struct domain *d = v->domain;
     struct segment_register reg;
-    typeof(v->arch.xsave_area->fpu_sse) *fpu_ctxt = v->arch.fpu_ctxt;
 
     domain_lock(d);
 
@@ -3892,14 +3877,9 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, 
uint16_t ip)
         v->arch.guest_table = pagetable_null();
     }
 
-    memset(fpu_ctxt, 0, sizeof(*fpu_ctxt));
-    fpu_ctxt->fcw = FCW_RESET;
-    fpu_ctxt->mxcsr = MXCSR_DEFAULT;
     if ( v->arch.xsave_area )
-    {
-        v->arch.xsave_area->xsave_hdr.xstate_bv = X86_XCR0_FP;
-        v->arch.xsave_area->xsave_hdr.xcomp_bv = 0;
-    }
+        v->arch.xsave_area->xsave_hdr.xstate_bv = 0;
+    vcpu_setup_fpu(v, v->arch.xsave_area, NULL, FCW_RESET);
 
     v->arch.vgc_flags = VGCF_online;
     memset(&v->arch.user_regs, 0, sizeof(v->arch.user_regs));
diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c
index a1d128dd94..00cf6bd370 100644
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -337,6 +337,49 @@ int vcpu_init_fpu(struct vcpu *v)
     return rc;
 }
 
+void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area,
+                    const void *data, unsigned int fcw_default)
+{
+    /*
+     * For the entire function please note that vcpu_init_fpu() (above) points
+     * v->arch.fpu_ctxt into v->arch.xsave_area when XSAVE is available. Hence
+     * accesses through both pointers alias one another, and the shorter form
+     * is used here.
+     */
+    typeof(xsave_area->fpu_sse) *fpu_sse = v->arch.fpu_ctxt;
+
+    ASSERT(!xsave_area || xsave_area == v->arch.xsave_area);
+
+    v->fpu_initialised = !!data;
+
+    if ( data )
+    {
+        memcpy(fpu_sse, data, sizeof(*fpu_sse));
+        if ( xsave_area )
+            xsave_area->xsave_hdr.xstate_bv = XSTATE_FP_SSE;
+    }
+    else if ( xsave_area && fcw_default == FCW_DEFAULT )
+    {
+        xsave_area->xsave_hdr.xstate_bv = 0;
+        fpu_sse->mxcsr = MXCSR_DEFAULT;
+    }
+    else
+    {
+        memset(fpu_sse, 0, sizeof(*fpu_sse));
+        fpu_sse->fcw = fcw_default;
+        fpu_sse->mxcsr = MXCSR_DEFAULT;
+        if ( v->arch.xsave_area )
+        {
+            v->arch.xsave_area->xsave_hdr.xstate_bv &= ~XSTATE_FP_SSE;
+            if ( fcw_default != FCW_DEFAULT )
+                v->arch.xsave_area->xsave_hdr.xstate_bv |= X86_XCR0_FP;
+        }
+    }
+
+    if ( xsave_area )
+        xsave_area->xsave_hdr.xcomp_bv = 0;
+}
+
 /* Free FPU's context save area */
 void vcpu_destroy_fpu(struct vcpu *v)
 {
diff --git a/xen/include/asm-x86/i387.h b/xen/include/asm-x86/i387.h
index 243de672eb..434a7761a5 100644
--- a/xen/include/asm-x86/i387.h
+++ b/xen/include/asm-x86/i387.h
@@ -34,5 +34,8 @@ void vcpu_save_fpu(struct vcpu *v);
 void save_fpu_enable(void);
 
 int vcpu_init_fpu(struct vcpu *v);
+struct xsave_struct;
+void vcpu_setup_fpu(struct vcpu *v, struct xsave_struct *xsave_area,
+                    const void *data, unsigned int fcw_default);
 void vcpu_destroy_fpu(struct vcpu *v);
 #endif /* __ASM_I386_I387_H */
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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