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Commit 5840c84b authored by Mukesh Rathor's avatar Mukesh Rathor Committed by Konrad Rzeszutek Wilk
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xen/pvh: Secondary VCPU bringup (non-bootup CPUs) 



The VCPU bringup protocol follows the PV with certain twists.
From xen/include/public/arch-x86/xen.h:

Also note that when calling DOMCTL_setvcpucontext and VCPU_initialise
for HVM and PVH guests, not all information in this structure is updated:

 - For HVM guests, the structures read include: fpu_ctxt (if
 VGCT_I387_VALID is set), flags, user_regs, debugreg[*]

 - PVH guests are the same as HVM guests, but additionally use ctrlreg[3] to
 set cr3. All other fields not used should be set to 0.

This is what we do. We piggyback on the 'xen_setup_gdt' - but modify
a bit - we need to call 'load_percpu_segment' so that 'switch_to_new_gdt'
can load per-cpu data-structures. It has no effect on the VCPU0.

We also piggyback on the %rdi register to pass in the CPU number - so
that when we bootup a new CPU, the cpu_bringup_and_idle will have
passed as the first parameter the CPU number (via %rdi for 64-bit).

Signed-off-by: default avatarMukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 8d656bbe

arch/x86/xen/enlighten.c

+8 −3
Original line number Diff line number Diff line
@@ -1409,14 +1409,19 @@ static void __init xen_boot_params_init_edd(void) 
 * Set up the GDT and segment registers for -fstack-protector.  Until

 * we do this, we have to be careful not to call any stack-protected

 * function, which is most of the kernel.

 *

 * Note, that it is __ref because the only caller of this after init

 * is PVH which is not going to use xen_load_gdt_boot or other

 * __init functions.

 */

static void __init xen_setup_gdt(void)

void __ref xen_setup_gdt(int cpu)

{

	if (xen_feature(XENFEAT_auto_translated_physmap)) {

#ifdef CONFIG_X86_64

		unsigned long dummy;



		switch_to_new_gdt(0); /* GDT and GS set */

		load_percpu_segment(cpu); /* We need to access per-cpu area */

		switch_to_new_gdt(cpu); /* GDT and GS set */



		/* We are switching of the Xen provided GDT to our HVM mode

		 * GDT. The new GDT has  __KERNEL_CS with CS.L = 1
@@ -1529,7 +1534,7 @@ asmlinkage void __init xen_start_kernel(void) 
	 * Set up kernel GDT and segment registers, mainly so that

	 * -fstack-protector code can be executed.

	 */

	xen_setup_gdt();

	xen_setup_gdt(0);



	xen_init_irq_ops();

	xen_init_cpuid_mask();

arch/x86/xen/smp.c

+33 −16
Original line number Diff line number Diff line
@@ -73,9 +73,11 @@ static void cpu_bringup(void) 
	touch_softlockup_watchdog();

	preempt_disable();



	/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */

	if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {

		xen_enable_sysenter();

		xen_enable_syscall();



	}

	cpu = smp_processor_id();

	smp_store_cpu_info(cpu);

	cpu_data(cpu).x86_max_cores = 1;
@@ -97,8 +99,14 @@ static void cpu_bringup(void) 
	wmb();			/* make sure everything is out */

}



static void cpu_bringup_and_idle(void)

/* Note: cpu parameter is only relevant for PVH */

static void cpu_bringup_and_idle(int cpu)

{

#ifdef CONFIG_X86_64

	if (xen_feature(XENFEAT_auto_translated_physmap) &&

	    xen_feature(XENFEAT_supervisor_mode_kernel))

		xen_setup_gdt(cpu);

#endif

	cpu_bringup();

	cpu_startup_entry(CPUHP_ONLINE);

}
@@ -274,8 +282,9 @@ static void __init xen_smp_prepare_boot_cpu(void) 
	native_smp_prepare_boot_cpu();



	if (xen_pv_domain()) {

		/* We've switched to the "real" per-cpu gdt, so make sure the

		   old memory can be recycled */

		if (!xen_feature(XENFEAT_writable_page_tables))

			/* We've switched to the "real" per-cpu gdt, so make

			 * sure the old memory can be recycled. */

			make_lowmem_page_readwrite(xen_initial_gdt);



#ifdef CONFIG_X86_32
@@ -360,22 +369,21 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) 


	gdt = get_cpu_gdt_table(cpu);



	ctxt->flags = VGCF_IN_KERNEL;

	ctxt->user_regs.ss = __KERNEL_DS;

#ifdef CONFIG_X86_32

	/* Note: PVH is not yet supported on x86_32. */

	ctxt->user_regs.fs = __KERNEL_PERCPU;

	ctxt->user_regs.gs = __KERNEL_STACK_CANARY;

#else

	ctxt->gs_base_kernel = per_cpu_offset(cpu);

#endif

	ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;



	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));



	{

	if (!xen_feature(XENFEAT_auto_translated_physmap)) {

		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;



		xen_copy_trap_info(ctxt->trap_ctxt);
@@ -396,18 +404,27 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) 
#ifdef CONFIG_X86_32

		ctxt->event_callback_cs     = __KERNEL_CS;

		ctxt->failsafe_callback_cs  = __KERNEL_CS;

#else

		ctxt->gs_base_kernel = per_cpu_offset(cpu);

#endif

		ctxt->event_callback_eip    =

					(unsigned long)xen_hypervisor_callback;

		ctxt->failsafe_callback_eip =

					(unsigned long)xen_failsafe_callback;

	}

		ctxt->user_regs.cs = __KERNEL_CS;

	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);



		per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);

#ifdef CONFIG_X86_32

	}

#else

	} else

		/* N.B. The user_regs.eip (cpu_bringup_and_idle) is called with

		 * %rdi having the cpu number - which means are passing in

		 * as the first parameter the cpu. Subtle!

		 */

		ctxt->user_regs.rdi = cpu;

#endif

	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);

	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));



	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))

		BUG();

arch/x86/xen/xen-ops.h

+1 −0
Original line number Diff line number Diff line
@@ -123,4 +123,5 @@ __visible void xen_adjust_exception_frame(void); 


extern int xen_panic_handler_init(void);



void xen_setup_gdt(int cpu);

#endif /* XEN_OPS_H */