Commit 564d261687c0 ("x86/ctxt-switch: Document and improve GDT handling") put
the initialisation of {,compat_}gdt_l1e into traps_init() but this wasn't a
great choice. Instead, put it in smp_prepare_cpus() which performs the BSP
preparation of variables normally set up by cpu_smpboot_alloc() for APs.
This removes an implicit dependency that prevents traps_init() moving earlier
than move_xen() in the boot sequence.
No functional change.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
v4:
* New
I'm on the fence about the ASSERT(), but I'm getting rather tired of unstated
dependencies. For a PV64 guest using SYSEXIT to enter the guest, it's the
first interrupt/exception which references the GDT, which could be after the
guest is running.
---
xen/arch/x86/domain.c | 2 ++
xen/arch/x86/smpboot.c | 11 +++++++++++
xen/arch/x86/traps-setup.c | 7 -------
3 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 8eb1509782ef..e658c2d647b7 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2029,6 +2029,8 @@ static always_inline bool need_full_gdt(const struct domain *d)
static void update_xen_slot_in_full_gdt(const struct vcpu *v, unsigned int cpu)
{
+ ASSERT(per_cpu(gdt_l1e, cpu).l1); /* Confirm these have been cached. */
+
l1e_write(pv_gdt_ptes(v) + FIRST_RESERVED_GDT_PAGE,
!is_pv_32bit_vcpu(v) ? per_cpu(gdt_l1e, cpu)
: per_cpu(compat_gdt_l1e, cpu));
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 961bdf53331c..491cbbba33ae 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -1167,6 +1167,17 @@ void __init smp_prepare_cpus(void)
initialize_cpu_data(0); /* Final full version of the data */
print_cpu_info(0);
+ /*
+ * Cache {,compat_}gdt_l1e for the BSP now that physically relocation is
+ * done. It must be after physical relocation of Xen, and before the
+ * first context_switch().
+ */
+ this_cpu(gdt_l1e) =
+ l1e_from_pfn(virt_to_mfn(boot_gdt), __PAGE_HYPERVISOR_RW);
+ if ( IS_ENABLED(CONFIG_PV32) )
+ this_cpu(compat_gdt_l1e) =
+ l1e_from_pfn(virt_to_mfn(boot_compat_gdt), __PAGE_HYPERVISOR_RW);
+
boot_cpu_physical_apicid = get_apic_id();
x86_cpu_to_apicid[0] = boot_cpu_physical_apicid;
diff --git a/xen/arch/x86/traps-setup.c b/xen/arch/x86/traps-setup.c
index d77be8f83921..c5fc71c75bca 100644
--- a/xen/arch/x86/traps-setup.c
+++ b/xen/arch/x86/traps-setup.c
@@ -341,13 +341,6 @@ void __init traps_init(void)
init_ler();
- /* Cache {,compat_}gdt_l1e now that physically relocation is done. */
- this_cpu(gdt_l1e) =
- l1e_from_pfn(virt_to_mfn(boot_gdt), __PAGE_HYPERVISOR_RW);
- if ( IS_ENABLED(CONFIG_PV32) )
- this_cpu(compat_gdt_l1e) =
- l1e_from_pfn(virt_to_mfn(boot_compat_gdt), __PAGE_HYPERVISOR_RW);
-
percpu_traps_init();
}
--
2.39.5