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Merge tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

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Pull three xen bug-fixes from Konrad Rzeszutek Wilk:
 - Revert the kexec fix which caused on non-kexec shutdowns a race.
 - Reuse existing P2M leafs - instead of requiring to allocate a large
   area of bootup virtual address estate.
 - Fix a one-off error when adding PFNs for balloon pages.

* tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/setup: Fix one-off error when adding for-balloon PFNs to the P2M.
  xen/p2m: Reuse existing P2M leafs if they are filled with 1:1 PFNs or INVALID.
  Revert "xen PVonHVM: move shared_info to MMIO before kexec"
This commit is contained in:
Linus Torvalds
2012-08-25 17:31:59 -07:00
parent 4ae4614712 c96aae1f7f
commit 267560874c
7 changed files with 113 additions and 130 deletions
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118
arch/x86/xen/enlighten.c
View File

@@ -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>
@@ -1470,130 +1469,38 @@ 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;
@@ -1644,9 +1551,6 @@ 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;