Re: fixed location of share info page in HVM guests

[Olaf Hering <olaf@aepfle.de>]

On Wed, Oct 24, Jan Beulich wrote:

> >>> On 23.10.12 at 21:49, Olaf Hering <olaf@aepfle.de> wrote:
> > The open question is when to switch from early_ioremap to
> > ioremap. Then the change to drivers/xen/platform-pci.c can be removed.
> 
> Wouldn't you be better of using
> early_set_fixmap(FIX_PARAVIRT_BOOTMAP, ...) anyway? If not,
> mm_init() (due to its calling of vmalloc_init()) would be the apparent
> boundary between using early and normal ioremaps.

set_fixmap seems to work. This patch works for me, with kexec and
save/restore.


Olaf

---
 arch/x86/include/asm/xen/hypervisor.h |  2 ++
 arch/x86/xen/enlighten.c              | 41 +++++++++++++++++++++++++----------
 arch/x86/xen/suspend.c                |  2 +-
 arch/x86/xen/xen-ops.h                |  2 +-
 4 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 66d0fff..e29a02b 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -34,6 +34,8 @@
 #define _ASM_X86_XEN_HYPERVISOR_H
 
 /* arch/i386/kernel/setup.c */
+#define HVM_SHARED_INFO_ADDR 0xFE700000UL
+
 extern struct shared_info *HYPERVISOR_shared_info;
 extern struct start_info *xen_start_info;
 
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index e3497f2..2cf40c9 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -103,7 +103,6 @@ struct shared_info xen_dummy_shared_info;
 
 void *xen_initial_gdt;
 
-RESERVE_BRK(shared_info_page_brk, PAGE_SIZE);
 __read_mostly int xen_have_vector_callback;
 EXPORT_SYMBOL_GPL(xen_have_vector_callback);
 
@@ -1497,38 +1496,56 @@ asmlinkage void __init xen_start_kernel(void)
 #endif
 }
 
-void __ref xen_hvm_init_shared_info(void)
+#ifdef CONFIG_XEN_PVHVM
+static struct shared_info *xen_hvm_shared_info;
+
+static void xen_hvm_connect_shared_info(unsigned long pfn)
 {
-	int cpu;
 	struct xen_add_to_physmap xatp;
-	static struct shared_info *shared_info_page = 0;
 
-	if (!shared_info_page)
-		shared_info_page = (struct shared_info *)
-			extend_brk(PAGE_SIZE, PAGE_SIZE);
 	xatp.domid = DOMID_SELF;
 	xatp.idx = 0;
 	xatp.space = XENMAPSPACE_shared_info;
-	xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
+	xatp.gpfn = pfn;
 	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
 		BUG();
 
-	HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
+}
+static void xen_hvm_set_shared_info(struct shared_info *sip)
+{
+	int cpu;
+
+	HYPERVISOR_shared_info = sip;
 
 	/* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
 	 * page, we use it in the event channel upcall and in some pvclock
 	 * related functions. We don't need the vcpu_info placement
 	 * optimizations because we don't use any pv_mmu or pv_irq op on
 	 * HVM.
-	 * When xen_hvm_init_shared_info is run at boot time only vcpu 0 is
-	 * online but xen_hvm_init_shared_info is run at resume time too and
+	 * When xen_hvm_set_shared_info is run at boot time only vcpu 0 is
+	 * online but xen_hvm_set_shared_info is run at resume time too and
 	 * in that case multiple vcpus might be online. */
 	for_each_online_cpu(cpu) {
 		per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
 	}
 }
 
-#ifdef CONFIG_XEN_PVHVM
+/* Reconnect the shared_info pfn to a (new) mfn */
+void xen_hvm_resume_shared_info(void)
+{
+	xen_hvm_connect_shared_info(HVM_SHARED_INFO_ADDR >> PAGE_SHIFT);
+}
+
+/* Obtain an address to the pfn in reserved area */
+static void __init xen_hvm_init_shared_info(void)
+{
+	set_fixmap(FIX_PARAVIRT_BOOTMAP, HVM_SHARED_INFO_ADDR);
+	xen_hvm_shared_info =
+		(struct shared_info *)fix_to_virt(FIX_PARAVIRT_BOOTMAP);
+	xen_hvm_connect_shared_info(HVM_SHARED_INFO_ADDR >> PAGE_SHIFT);
+	xen_hvm_set_shared_info(xen_hvm_shared_info);
+}
+
 static void __init init_hvm_pv_info(void)
 {
 	int major, minor;
diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index 45329c8..ae8a00c 100644
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -30,7 +30,7 @@ void xen_arch_hvm_post_suspend(int suspend_cancelled)
 {
 #ifdef CONFIG_XEN_PVHVM
 	int cpu;
-	xen_hvm_init_shared_info();
+	xen_hvm_resume_shared_info();
 	xen_callback_vector();
 	xen_unplug_emulated_devices();
 	if (xen_feature(XENFEAT_hvm_safe_pvclock)) {
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index a95b417..d2e73d1 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -40,7 +40,7 @@ void xen_enable_syscall(void);
 void xen_vcpu_restore(void);
 
 void xen_callback_vector(void);
-void xen_hvm_init_shared_info(void);
+void xen_hvm_resume_shared_info(void);
 void xen_unplug_emulated_devices(void);
 
 void __init xen_build_dynamic_phys_to_machine(void);
-- 
1.7.12.4