x86/xen/64, x86/entry/64: Clean up SP code in cpu_initialize_context()

commit f16b3da1dc936c0f8121741d0a1731bf242f2f56 upstream.

I'm removing thread_struct::sp0, and Xen's usage of it is slightly
dubious and unnecessary.  Use appropriate helpers instead.

While we're at at, reorder the code slightly to make it more obvious
what's going on.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d5b9a3da2b47c68325bd2bbe8f82d9554dee0d0f.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index 05f91ce9b55eea1519a900dd57a48a29f6c08da1..c0c756c76afebf08d282fb35c2fc49b641120bb4 100644 (file)
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -14,6 +14,7 @@
  * single-threaded.
  */
 #include <linux/sched.h>
+#include <linux/sched/task_stack.h>
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/smp.h>
@@ -294,12 +295,19 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 #endif
        memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 
+       /*
+        * Bring up the CPU in cpu_bringup_and_idle() with the stack
+        * pointing just below where pt_regs would be if it were a normal
+        * kernel entry.
+        */
        ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
        ctxt->flags = VGCF_IN_KERNEL;
        ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
        ctxt->user_regs.ds = __USER_DS;
        ctxt->user_regs.es = __USER_DS;
        ctxt->user_regs.ss = __KERNEL_DS;
+       ctxt->user_regs.cs = __KERNEL_CS;
+       ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
 
        xen_copy_trap_info(ctxt->trap_ctxt);
 
@@ -314,8 +322,13 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
        ctxt->gdt_frames[0] = gdt_mfn;
        ctxt->gdt_ents      = GDT_ENTRIES;
 
+       /*
+        * Set SS:SP that Xen will use when entering guest kernel mode
+        * from guest user mode.  Subsequent calls to load_sp0() can
+        * change this value.
+        */
        ctxt->kernel_ss = __KERNEL_DS;
-       ctxt->kernel_sp = idle->thread.sp0;
+       ctxt->kernel_sp = task_top_of_stack(idle);
 
 #ifdef CONFIG_X86_32
        ctxt->event_callback_cs     = __KERNEL_CS;
@@ -327,10 +340,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
                (unsigned long)xen_hypervisor_callback;
        ctxt->failsafe_callback_eip =
                (unsigned long)xen_failsafe_callback;
-       ctxt->user_regs.cs = __KERNEL_CS;
        per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
 
-       ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
        ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
        if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
                BUG();