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Three bug-fixes: 

- 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.
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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

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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;

95
arch/x86/xen/p2m.c
View File

@ -196,9 +196,11 @@ RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
/* When we populate back during bootup, the amount of pages can vary. The
* max we have is seen is 395979, but that does not mean it can't be more.
* But some machines can have 3GB I/O holes even. So lets reserve enough
* for 4GB of I/O and E820 holes. */
RESERVE_BRK(p2m_populated, PMD_SIZE * 4);
* Some machines can have 3GB I/O holes even. With early_can_reuse_p2m_middle
* it can re-use Xen provided mfn_list array, so we only need to allocate at
* most three P2M top nodes. */
RESERVE_BRK(p2m_populated, PAGE_SIZE * 3);
static inline unsigned p2m_top_index(unsigned long pfn)
{
BUG_ON(pfn >= MAX_P2M_PFN);
@ -575,12 +577,99 @@ static bool __init early_alloc_p2m(unsigned long pfn)
}
return true;
}
/*
* Skim over the P2M tree looking at pages that are either filled with
* INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
* replace the P2M leaf with a p2m_missing or p2m_identity.
* Stick the old page in the new P2M tree location.
*/
bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn)
{
unsigned topidx;
unsigned mididx;
unsigned ident_pfns;
unsigned inv_pfns;
unsigned long *p2m;
unsigned long *mid_mfn_p;
unsigned idx;
unsigned long pfn;
/* We only look when this entails a P2M middle layer */
if (p2m_index(set_pfn))
return false;
for (pfn = 0; pfn <= MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
topidx = p2m_top_index(pfn);
if (!p2m_top[topidx])
continue;
if (p2m_top[topidx] == p2m_mid_missing)
continue;
mididx = p2m_mid_index(pfn);
p2m = p2m_top[topidx][mididx];
if (!p2m)
continue;
if ((p2m == p2m_missing) || (p2m == p2m_identity))
continue;
if ((unsigned long)p2m == INVALID_P2M_ENTRY)
continue;
ident_pfns = 0;
inv_pfns = 0;
for (idx = 0; idx < P2M_PER_PAGE; idx++) {
/* IDENTITY_PFNs are 1:1 */
if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
ident_pfns++;
else if (p2m[idx] == INVALID_P2M_ENTRY)
inv_pfns++;
else
break;
}
if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
goto found;
}
return false;
found:
/* Found one, replace old with p2m_identity or p2m_missing */
p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
/* And the other for save/restore.. */
mid_mfn_p = p2m_top_mfn_p[topidx];
/* NOTE: Even if it is a p2m_identity it should still be point to
* a page filled with INVALID_P2M_ENTRY entries. */
mid_mfn_p[mididx] = virt_to_mfn(p2m_missing);
/* Reset where we want to stick the old page in. */
topidx = p2m_top_index(set_pfn);
mididx = p2m_mid_index(set_pfn);
/* This shouldn't happen */
if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
early_alloc_p2m(set_pfn);
if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
return false;
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
mid_mfn_p = p2m_top_mfn_p[topidx];
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
}
bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
if (!early_alloc_p2m(pfn))
return false;
if (early_can_reuse_p2m_middle(pfn, mfn))
return __set_phys_to_machine(pfn, mfn);
if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/))
return false;

9
arch/x86/xen/setup.c
View File

@ -78,9 +78,16 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
memblock_reserve(start, size);
xen_max_p2m_pfn = PFN_DOWN(start + size);
for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
unsigned long mfn = pfn_to_mfn(pfn);
if (WARN(mfn == pfn, "Trying to over-write 1-1 mapping (pfn: %lx)\n", pfn))
continue;
WARN(mfn != INVALID_P2M_ENTRY, "Trying to remove %lx which has %lx mfn!\n",
pfn, mfn);
for (pfn = PFN_DOWN(start); pfn <= xen_max_p2m_pfn; pfn++)
__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
}
}
static unsigned long __init xen_do_chunk(unsigned long start,

2
arch/x86/xen/suspend.c
View File

@ -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)) {

2
arch/x86/xen/xen-ops.h
View File

@ -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);

15
drivers/xen/platform-pci.c
View File

@ -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) {

2
include/xen/events.h
View File

@ -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);