xen: set IO permission early (before early_cpu_init())

This patch is based off "xen dom0: Set up basic IO permissions for dom0."
by Juan Quintela <quintela@redhat.com>.

On AMD machines when we boot the kernel as Domain 0 we get this nasty:

mapping kernel into physical memory
Xen: setup ISA identity maps
about to get started...
(XEN) traps.c:475:d0 Unhandled general protection fault fault/trap [#13] on VCPU 0 [ec=0000]
(XEN) domain_crash_sync called from entry.S
(XEN) Domain 0 (vcpu#0) crashed on cpu#0:
(XEN) ----[ Xen-4.1-101116  x86_64  debug=y  Not tainted ]----
(XEN) CPU:    0
(XEN) RIP:    e033:[<ffffffff8130271b>]
(XEN) RFLAGS: 0000000000000282   EM: 1   CONTEXT: pv guest
(XEN) rax: 000000008000c068   rbx: ffffffff8186c680   rcx: 0000000000000068
(XEN) rdx: 0000000000000cf8   rsi: 000000000000c000   rdi: 0000000000000000
(XEN) rbp: ffffffff81801e98   rsp: ffffffff81801e50   r8:  ffffffff81801eac
(XEN) r9:  ffffffff81801ea8   r10: ffffffff81801eb4   r11: 00000000ffffffff
(XEN) r12: ffffffff8186c694   r13: ffffffff81801f90   r14: ffffffffffffffff
(XEN) r15: 0000000000000000   cr0: 000000008005003b   cr4: 00000000000006f0
(XEN) cr3: 0000000221803000   cr2: 0000000000000000
(XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e02b   cs: e033
(XEN) Guest stack trace from rsp=ffffffff81801e50:

RIP points to read_pci_config() function.

The issue is that we don't set IO permissions for the Linux kernel early enough.

The call sequence used to be:

    xen_start_kernel()
	x86_init.oem.arch_setup = xen_setup_arch;
        setup_arch:
           - early_cpu_init
               - early_init_amd
                  - read_pci_config
           - x86_init.oem.arch_setup [ xen_arch_setup ]
               - set IO permissions.

We need to set the IO permissions earlier on, which this patch does.

Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bd35549..7250bef 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1095,6 +1095,8 @@ static void __init xen_setup_stackprotector(void)
 /* First C function to be called on Xen boot */
 asmlinkage void __init xen_start_kernel(void)
 {
+       struct physdev_set_iopl set_iopl;
+       int rc;
        pgd_t *pgd;
 
        if (!xen_start_info)
@@ -1209,10 +1211,18 @@ asmlinkage void __init xen_start_kernel(void)
 #else
        pv_info.kernel_rpl = 0;
 #endif
-
        /* set the limit of our address space */
        xen_reserve_top();
 
+       /* We used to do this in xen_arch_setup, but that is too late on AMD
+        * were early_cpu_init (run before ->arch_setup()) calls early_amd_init
+        * which pokes 0xcf8 port.
+        */
+       set_iopl.iopl = 1;
+       rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
+       if (rc != 0)
+               xen_raw_printk("physdev_op failed %d\n", rc);
+
 #ifdef CONFIG_X86_32
        /* set up basic CPUID stuff */
        cpu_detect(&new_cpu_data);

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 630fb53..38fdffa 100644 (file)
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -336,9 +336,6 @@ void __cpuinit xen_enable_syscall(void)
 
 void __init xen_arch_setup(void)
 {
-       struct physdev_set_iopl set_iopl;
-       int rc;
-
        xen_panic_handler_init();
 
        HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);
@@ -355,11 +352,6 @@ void __init xen_arch_setup(void)
        xen_enable_sysenter();
        xen_enable_syscall();
 
-       set_iopl.iopl = 1;
-       rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
-       if (rc != 0)
-               printk(KERN_INFO "physdev_op failed %d\n", rc);
-
 #ifdef CONFIG_ACPI
        if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
                printk(KERN_INFO "ACPI in unprivileged domain disabled\n");