libxc: create an initial FPU state for HVM guests

Xen always set the FPU as initialized when loading a HVM context, so libxc
has to provide a valid FPU context when setting the CPU registers.

This is a stop-gap measure in order to unblock OSSTest Windows 7 failures
while a proper fix for the HVM CPU save/restore is being worked on.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Suggested-by: Jan Beulich <jbeulich@suse.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index dd331bf71e7b43a5332953fc52675d74b2fe1d7e..034abe0875392734718c2ae91450681e70b3f05f 100644 (file)
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -841,6 +841,27 @@ static int vcpu_hvm(struct xc_dom_image *dom)
         struct hvm_save_descriptor end_d;
         HVM_SAVE_TYPE(END) end;
     } bsp_ctx;
+    /*
+     * The layout of the fpu context structure is the same for
+     * both 32 and 64 bits.
+     */
+    struct {
+        uint16_t fcw;
+        uint16_t fsw;
+        uint8_t ftw;
+        uint8_t rsvd1;
+        uint16_t fop;
+        union {
+            uint64_t addr;
+            struct {
+                uint32_t offs;
+                uint16_t sel;
+                uint16_t rsvd;
+            };
+        } fip, fdp;
+        uint32_t mxcsr;
+        uint32_t mxcsr_mask;
+    } *fpu_ctxt;
     uint8_t *full_ctx = NULL;
     int rc;
 
@@ -908,6 +929,23 @@ static int vcpu_hvm(struct xc_dom_image *dom)
     /* Set the control registers. */
     bsp_ctx.cpu.cr0 = X86_CR0_PE | X86_CR0_ET;
 
+    /*
+     * XXX: Set initial FPU state.
+     *
+     * This should be removed once Xen is able to know if the
+     * FPU state saved is valid or not, now Xen always sets
+     * fpu_initialised to true regardless of the FPU state.
+     *
+     * The code below mimics the FPU sate after executing
+     * fninit
+     * ldmxcsr 0x1f80
+     */
+    fpu_ctxt = (typeof(fpu_ctxt))bsp_ctx.cpu.fpu_regs;
+
+    fpu_ctxt->fcw = 0x37f;
+    fpu_ctxt->ftw = 0xff;
+    fpu_ctxt->mxcsr = 0x1f80;
+
     /* Set the IP. */
     bsp_ctx.cpu.rip = dom->parms.phys_entry;