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Date: Thu, 16 Aug 2012 11:50:14 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH 2/2] Revert "xen PVonHVM: move shared_info to MMIO before kexec"
This reverts commit 00e37bdb0113a98408de42db85be002f21dbffd3.
During shutdown of PVHVM guests with more than 2VCPUs on certain
machines we can hit the race where the replaced shared_info is not
replaced fast enough and the PV time clock retries reading the same
area over and over without any success and is stuck in an
infinite loop.
Acked-by: Olaf Hering <olaf@...fle.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
arch/x86/xen/enlighten.c | 118 ++++---------------------------------------
arch/x86/xen/suspend.c | 2 +-
arch/x86/xen/xen-ops.h | 2 +-
drivers/xen/platform-pci.c | 15 ------
include/xen/events.h | 2 -
5 files changed, 13 insertions(+), 126 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index a6f8acb..f1814fc 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -31,7 +31,6 @@
#include <linux/pci.h>
#include <linux/gfp.h>
#include <linux/memblock.h>
-#include <linux/syscore_ops.h>
#include <xen/xen.h>
#include <xen/interface/xen.h>
@@ -1472,130 +1471,38 @@ asmlinkage void __init xen_start_kernel(void)
#endif
}
-#ifdef CONFIG_XEN_PVHVM
-/*
- * The pfn containing the shared_info is located somewhere in RAM. This
- * will cause trouble if the current kernel is doing a kexec boot into a
- * new kernel. The new kernel (and its startup code) can not know where
- * the pfn is, so it can not reserve the page. The hypervisor will
- * continue to update the pfn, and as a result memory corruption occours
- * in the new kernel.
- *
- * One way to work around this issue is to allocate a page in the
- * xen-platform pci device's BAR memory range. But pci init is done very
- * late and the shared_info page is already in use very early to read
- * the pvclock. So moving the pfn from RAM to MMIO is racy because some
- * code paths on other vcpus could access the pfn during the small
- * window when the old pfn is moved to the new pfn. There is even a
- * small window were the old pfn is not backed by a mfn, and during that
- * time all reads return -1.
- *
- * Because it is not known upfront where the MMIO region is located it
- * can not be used right from the start in xen_hvm_init_shared_info.
- *
- * To minimise trouble the move of the pfn is done shortly before kexec.
- * This does not eliminate the race because all vcpus are still online
- * when the syscore_ops will be called. But hopefully there is no work
- * pending at this point in time. Also the syscore_op is run last which
- * reduces the risk further.
- */
-
-static struct shared_info *xen_hvm_shared_info;
-
-static void xen_hvm_connect_shared_info(unsigned long pfn)
+void __ref xen_hvm_init_shared_info(void)
{
+ 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 = pfn;
+ xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
BUG();
-}
-static void xen_hvm_set_shared_info(struct shared_info *sip)
-{
- int cpu;
-
- HYPERVISOR_shared_info = sip;
+ HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
/* 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_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
+ * 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
* in that case multiple vcpus might be online. */
for_each_online_cpu(cpu) {
per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
}
}
-/* Reconnect the shared_info pfn to a mfn */
-void xen_hvm_resume_shared_info(void)
-{
- xen_hvm_connect_shared_info(__pa(xen_hvm_shared_info) >> PAGE_SHIFT);
-}
-
-#ifdef CONFIG_KEXEC
-static struct shared_info *xen_hvm_shared_info_kexec;
-static unsigned long xen_hvm_shared_info_pfn_kexec;
-
-/* Remember a pfn in MMIO space for kexec reboot */
-void __devinit xen_hvm_prepare_kexec(struct shared_info *sip, unsigned long pfn)
-{
- xen_hvm_shared_info_kexec = sip;
- xen_hvm_shared_info_pfn_kexec = pfn;
-}
-
-static void xen_hvm_syscore_shutdown(void)
-{
- struct xen_memory_reservation reservation = {
- .domid = DOMID_SELF,
- .nr_extents = 1,
- };
- unsigned long prev_pfn;
- int rc;
-
- if (!xen_hvm_shared_info_kexec)
- return;
-
- prev_pfn = __pa(xen_hvm_shared_info) >> PAGE_SHIFT;
- set_xen_guest_handle(reservation.extent_start, &prev_pfn);
-
- /* Move pfn to MMIO, disconnects previous pfn from mfn */
- xen_hvm_connect_shared_info(xen_hvm_shared_info_pfn_kexec);
-
- /* Update pointers, following hypercall is also a memory barrier */
- xen_hvm_set_shared_info(xen_hvm_shared_info_kexec);
-
- /* Allocate new mfn for previous pfn */
- do {
- rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
- if (rc == 0)
- msleep(123);
- } while (rc == 0);
-
- /* Make sure the previous pfn is really connected to a (new) mfn */
- BUG_ON(rc != 1);
-}
-
-static struct syscore_ops xen_hvm_syscore_ops = {
- .shutdown = xen_hvm_syscore_shutdown,
-};
-#endif
-
-/* Use a pfn in RAM, may move to MMIO before kexec. */
-static void __init xen_hvm_init_shared_info(void)
-{
- /* Remember pointer for resume */
- xen_hvm_shared_info = extend_brk(PAGE_SIZE, PAGE_SIZE);
- xen_hvm_connect_shared_info(__pa(xen_hvm_shared_info) >> PAGE_SHIFT);
- xen_hvm_set_shared_info(xen_hvm_shared_info);
-}
-
+#ifdef CONFIG_XEN_PVHVM
static void __init init_hvm_pv_info(void)
{
int major, minor;
@@ -1646,9 +1553,6 @@ static void __init xen_hvm_guest_init(void)
init_hvm_pv_info();
xen_hvm_init_shared_info();
-#ifdef CONFIG_KEXEC
- register_syscore_ops(&xen_hvm_syscore_ops);
-#endif
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 ae8a00c..45329c8 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_resume_shared_info();
+ xen_hvm_init_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 1e4329e..202d4c1 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -41,7 +41,7 @@ void xen_enable_syscall(void);
void xen_vcpu_restore(void);
void xen_callback_vector(void);
-void xen_hvm_resume_shared_info(void);
+void xen_hvm_init_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 d4c50d6..97ca359 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -101,19 +101,6 @@ static int platform_pci_resume(struct pci_dev *pdev)
return 0;
}
-static void __devinit prepare_shared_info(void)
-{
-#ifdef CONFIG_KEXEC
- unsigned long addr;
- struct shared_info *hvm_shared_info;
-
- addr = alloc_xen_mmio(PAGE_SIZE);
- hvm_shared_info = ioremap(addr, PAGE_SIZE);
- memset(hvm_shared_info, 0, PAGE_SIZE);
- xen_hvm_prepare_kexec(hvm_shared_info, addr >> PAGE_SHIFT);
-#endif
-}
-
static int __devinit platform_pci_init(struct pci_dev *pdev,
const struct pci_device_id *ent)
{
@@ -151,8 +138,6 @@ static int __devinit platform_pci_init(struct pci_dev *pdev,
platform_mmio = mmio_addr;
platform_mmiolen = mmio_len;
- prepare_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 9c641de..04399b2 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -58,8 +58,6 @@ void notify_remote_via_irq(int irq);
void xen_irq_resume(void);
-void xen_hvm_prepare_kexec(struct shared_info *sip, unsigned long pfn);
-
/* 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);
--
1.7.7.6
--
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