Re: fixed location of share info page in HVM guests

[Olaf Hering <olaf@aepfle.de>]

On Fri, Aug 31, Konrad Rzeszutek Wilk wrote:

> On Tue, Aug 28, 2012 at 02:35:19PM +0100, Keir Fraser wrote:
> > On 28/08/2012 13:42, "Olaf Hering" <olaf@aepfle.de> wrote:
> > 
> > > On Tue, Aug 28, Keir Fraser wrote:
> > > 
> > >> Okay, that was a bit too clever, trying to hide between IOAPIC and LAPIC
> > >> pages. How about a bit lower in memory -- FE700000-FE7FFFFF?
> > >> 
> > >> Everything in range FC000000-FFFFFFFF should already be marked
> > >> E820_RESERVED. You can test that, and also see
> > >> tools/firmware/hvmloader/e820.c:build_e820_table() (and note that
> > >> RESERVED_MEMBASE == FC000000).
> > > 
> > > Yes, FC000000-FFFFFFFF has already an E820_RESERVED entry. Within that
> > > range the kernel finds the IOAPIC, LAPIC and the HPET, perhaps because
> > > they are listed in the ACPI table or because they are found by other
> > > ways.
> > 
> > Yes they are all listed in various ACPI tables.
> > 
> > > To make the location of the of the shared pages configurable from the
> > > tools, does tools/firmware/hvmloader/acpi/dsdt.asl have a way to
> > > describe such special region? Maybe the kernel parses that table early
> 
> Isn't there also a magic string of said structure? If so we should also
> check for the magic string to make sure we are mapping the proper
> "thing." It can be done similary to how iBFT or EBDA is found.

I will have a look if ACPI can be used that early, for the time being a
hardcoded address is used. This is the proposed kernel change, against
3.7-rc2. The open question is when to switch from early_ioremap to
ioremap. Then the change to drivers/xen/platform-pci.c can be removed.

Olaf

 xen PVonHVM: move shared_info to reserved memory area

---
 arch/x86/include/asm/xen/hypervisor.h |  2 ++
 arch/x86/xen/enlighten.c              | 53 ++++++++++++++++++++++++++---------
 arch/x86/xen/suspend.c                |  2 +-
 arch/x86/xen/xen-ops.h                |  2 +-
 drivers/xen/platform-pci.c            |  2 ++
 include/xen/events.h                  |  2 ++
 6 files changed, 48 insertions(+), 15 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..b051c3f 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 +1496,66 @@ 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);
+}
+
+/* Update shared_info address */
+void __devinit xen_hvm_init_shared_info(void)
+{
+	struct shared_info *early;
+
+	early = xen_hvm_shared_info;
+	xen_hvm_shared_info = ioremap(HVM_SHARED_INFO_ADDR, PAGE_SIZE);
+	xen_hvm_set_shared_info(xen_hvm_shared_info);
+	wmb();
+	early_iounmap(early, PAGE_SIZE);
+}
+
+/* Obtain an address to the pfn in reserved area */
+static void __init xen_hvm_early_init_shared_info(void)
+{
+	xen_hvm_shared_info = early_ioremap(HVM_SHARED_INFO_ADDR, PAGE_SIZE);
+	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;
@@ -1578,7 +1605,7 @@ static void __init xen_hvm_guest_init(void)
 {
 	init_hvm_pv_info();
 
-	xen_hvm_init_shared_info();
+	xen_hvm_early_init_shared_info();
 
 	if (xen_feature(XENFEAT_hvm_callback_vector))
 		xen_have_vector_callback = 1;
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);
diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
index 97ca359..989365f 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -138,6 +138,8 @@ static int __devinit platform_pci_init(struct pci_dev *pdev,
 	platform_mmio = mmio_addr;
 	platform_mmiolen = mmio_len;
 
+	xen_hvm_init_shared_info();
+
 	if (!xen_have_vector_callback) {
 		ret = xen_allocate_irq(pdev);
 		if (ret) {
diff --git a/include/xen/events.h b/include/xen/events.h
index c6bfe01..58c8431 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -58,6 +58,8 @@ void notify_remote_via_irq(int irq);
 
 void xen_irq_resume(void);
 
+void xen_hvm_init_shared_info(void);
+
 /* Clear an irq's pending state, in preparation for polling on it */
 void xen_clear_irq_pending(int irq);
 void xen_set_irq_pending(int irq);
-- 
1.7.12.4