linux/drivers/xen/platform-pci.c
Olaf Hering 00e37bdb01 xen PVonHVM: move shared_info to MMIO before kexec
Currently kexec in a PVonHVM guest fails with a triple fault because the
new kernel overwrites the shared info page. The exact failure depends on
the size of the kernel image. This patch moves the pfn from RAM into
MMIO space before the kexec boot.

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.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-07-19 15:52:05 -04:00

211 lines
4.9 KiB
C

/******************************************************************************
* platform-pci.c
*
* Xen platform PCI device driver
* Copyright (c) 2005, Intel Corporation.
* Copyright (c) 2007, XenSource Inc.
* Copyright (c) 2010, Citrix
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*
*/
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <xen/platform_pci.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/hvm.h>
#include <xen/xen-ops.h>
#define DRV_NAME "xen-platform-pci"
MODULE_AUTHOR("ssmith@xensource.com and stefano.stabellini@eu.citrix.com");
MODULE_DESCRIPTION("Xen platform PCI device");
MODULE_LICENSE("GPL");
static unsigned long platform_mmio;
static unsigned long platform_mmio_alloc;
static unsigned long platform_mmiolen;
static uint64_t callback_via;
unsigned long alloc_xen_mmio(unsigned long len)
{
unsigned long addr;
addr = platform_mmio + platform_mmio_alloc;
platform_mmio_alloc += len;
BUG_ON(platform_mmio_alloc > platform_mmiolen);
return addr;
}
static uint64_t get_callback_via(struct pci_dev *pdev)
{
u8 pin;
int irq;
irq = pdev->irq;
if (irq < 16)
return irq; /* ISA IRQ */
pin = pdev->pin;
/* We don't know the GSI. Specify the PCI INTx line instead. */
return ((uint64_t)0x01 << 56) | /* PCI INTx identifier */
((uint64_t)pci_domain_nr(pdev->bus) << 32) |
((uint64_t)pdev->bus->number << 16) |
((uint64_t)(pdev->devfn & 0xff) << 8) |
((uint64_t)(pin - 1) & 3);
}
static irqreturn_t do_hvm_evtchn_intr(int irq, void *dev_id)
{
xen_hvm_evtchn_do_upcall();
return IRQ_HANDLED;
}
static int xen_allocate_irq(struct pci_dev *pdev)
{
return request_irq(pdev->irq, do_hvm_evtchn_intr,
IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TRIGGER_RISING,
"xen-platform-pci", pdev);
}
static int platform_pci_resume(struct pci_dev *pdev)
{
int err;
if (xen_have_vector_callback)
return 0;
err = xen_set_callback_via(callback_via);
if (err) {
dev_err(&pdev->dev, "platform_pci_resume failure!\n");
return err;
}
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)
{
int i, ret;
long ioaddr;
long mmio_addr, mmio_len;
unsigned int max_nr_gframes;
if (!xen_domain())
return -ENODEV;
i = pci_enable_device(pdev);
if (i)
return i;
ioaddr = pci_resource_start(pdev, 0);
mmio_addr = pci_resource_start(pdev, 1);
mmio_len = pci_resource_len(pdev, 1);
if (mmio_addr == 0 || ioaddr == 0) {
dev_err(&pdev->dev, "no resources found\n");
ret = -ENOENT;
goto pci_out;
}
ret = pci_request_region(pdev, 1, DRV_NAME);
if (ret < 0)
goto pci_out;
ret = pci_request_region(pdev, 0, DRV_NAME);
if (ret < 0)
goto mem_out;
platform_mmio = mmio_addr;
platform_mmiolen = mmio_len;
prepare_shared_info();
if (!xen_have_vector_callback) {
ret = xen_allocate_irq(pdev);
if (ret) {
dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret);
goto out;
}
callback_via = get_callback_via(pdev);
ret = xen_set_callback_via(callback_via);
if (ret) {
dev_warn(&pdev->dev, "Unable to set the evtchn callback "
"err=%d\n", ret);
goto out;
}
}
max_nr_gframes = gnttab_max_grant_frames();
xen_hvm_resume_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
ret = gnttab_init();
if (ret)
goto out;
xenbus_probe(NULL);
return 0;
out:
pci_release_region(pdev, 0);
mem_out:
pci_release_region(pdev, 1);
pci_out:
pci_disable_device(pdev);
return ret;
}
static struct pci_device_id platform_pci_tbl[] __devinitdata = {
{PCI_VENDOR_ID_XEN, PCI_DEVICE_ID_XEN_PLATFORM,
PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0},
{0,}
};
MODULE_DEVICE_TABLE(pci, platform_pci_tbl);
static struct pci_driver platform_driver = {
.name = DRV_NAME,
.probe = platform_pci_init,
.id_table = platform_pci_tbl,
#ifdef CONFIG_PM
.resume_early = platform_pci_resume,
#endif
};
static int __init platform_pci_module_init(void)
{
return pci_register_driver(&platform_driver);
}
module_init(platform_pci_module_init);