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linux/drivers/xen/xen-pciback/pciback.h
Marek Marczykowski-Górecki 476878e4b2 xen-pciback: optionally allow interrupt enable flag writes 
QEMU running in a stubdom needs to be able to set INTX_DISABLE, and the
MSI(-X) enable flags in the PCI config space. This adds an attribute
'allow_interrupt_control' which when set for a PCI device allows writes
to this flag(s). The toolstack will need to set this for stubdoms.
When enabled, guest (stubdomain) will be allowed to set relevant enable
flags, but only one at a time - i.e. it refuses to enable more than one
of INTx, MSI, MSI-X at a time.

This functionality is needed only for config space access done by device
model (stubdomain) serving a HVM with the actual PCI device. It is not
necessary and unsafe to enable direct access to those bits for PV domain
with the device attached. For PV domains, there are separate protocol
messages (XEN_PCI_OP_{enable,disable}_{msi,msix}) for this purpose.
Those ops in addition to setting enable bits, also configure MSI(-X) in
dom0 kernel - which is undesirable for PCI passthrough to HVM guests.

This should not introduce any new security issues since a malicious
guest (or stubdom) can already generate MSIs through other ways, see
[1] page 8. Additionally, when qemu runs in dom0, it already have direct
access to those bits.

This is the second iteration of this feature. First was proposed as a
direct Xen interface through a new hypercall, but ultimately it was
rejected by the maintainer, because of mixing pciback and hypercalls for
PCI config space access isn't a good design. Full discussion at [2].

[1]: https://invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf
[2]: https://xen.markmail.org/thread/smpgpws4umdzizze

[part of the commit message and sysfs handling]
Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
[the rest]
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
[boris: A few small changes suggested by Roger, some formatting changes]
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-01-15 16:50:13 -06:00

196 lines
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* PCI Backend Common Data Structures & Function Declarations
*
* Author: Ryan Wilson <hap9@epoch.ncsc.mil>
*/
#ifndef __XEN_PCIBACK_H__
#define __XEN_PCIBACK_H__
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <xen/xenbus.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/atomic.h>
#include <xen/interface/io/pciif.h>
#define DRV_NAME "xen-pciback"
struct pci_dev_entry {
struct list_head list;
struct pci_dev *dev;
};
#define _PDEVF_op_active (0)
#define PDEVF_op_active (1<<(_PDEVF_op_active))
#define _PCIB_op_pending (1)
#define PCIB_op_pending (1<<(_PCIB_op_pending))
struct xen_pcibk_device {
void *pci_dev_data;
struct mutex dev_lock;
struct xenbus_device *xdev;
struct xenbus_watch be_watch;
u8 be_watching;
int evtchn_irq;
struct xen_pci_sharedinfo *sh_info;
unsigned long flags;
struct work_struct op_work;
struct xen_pci_op op;
};
struct xen_pcibk_dev_data {
struct list_head config_fields;
struct pci_saved_state *pci_saved_state;
unsigned int permissive:1;
unsigned int allow_interrupt_control:1;
unsigned int warned_on_write:1;
unsigned int enable_intx:1;
unsigned int isr_on:1; /* Whether the IRQ handler is installed. */
unsigned int ack_intr:1; /* .. and ACK-ing */
unsigned long handled;
unsigned int irq; /* Saved in case device transitions to MSI/MSI-X */
char irq_name[0]; /* xen-pcibk[000:04:00.0] */
};
/* Used by XenBus and xen_pcibk_ops.c */
extern wait_queue_head_t xen_pcibk_aer_wait_queue;
/* Used by pcistub.c and conf_space_quirks.c */
extern struct list_head xen_pcibk_quirks;
/* Get/Put PCI Devices that are hidden from the PCI Backend Domain */
struct pci_dev *pcistub_get_pci_dev_by_slot(struct xen_pcibk_device *pdev,
int domain, int bus,
int slot, int func);
struct pci_dev *pcistub_get_pci_dev(struct xen_pcibk_device *pdev,
struct pci_dev *dev);
void pcistub_put_pci_dev(struct pci_dev *dev);
/* Ensure a device is turned off or reset */
void xen_pcibk_reset_device(struct pci_dev *pdev);
/* Access a virtual configuration space for a PCI device */
int xen_pcibk_config_init(void);
int xen_pcibk_config_init_dev(struct pci_dev *dev);
void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev);
void xen_pcibk_config_reset_dev(struct pci_dev *dev);
void xen_pcibk_config_free_dev(struct pci_dev *dev);
int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
u32 *ret_val);
int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size,
u32 value);
/* Handle requests for specific devices from the frontend */
typedef int (*publish_pci_dev_cb) (struct xen_pcibk_device *pdev,
unsigned int domain, unsigned int bus,
unsigned int devfn, unsigned int devid);
typedef int (*publish_pci_root_cb) (struct xen_pcibk_device *pdev,
unsigned int domain, unsigned int bus);
/* Backend registration for the two types of BDF representation:
* vpci - BDFs start at 00
* passthrough - BDFs are exactly like in the host.
*/
struct xen_pcibk_backend {
const char *name;
int (*init)(struct xen_pcibk_device *pdev);
void (*free)(struct xen_pcibk_device *pdev);
int (*find)(struct pci_dev *pcidev, struct xen_pcibk_device *pdev,
unsigned int *domain, unsigned int *bus,
unsigned int *devfn);
int (*publish)(struct xen_pcibk_device *pdev, publish_pci_root_cb cb);
void (*release)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
bool lock);
int (*add)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
int devid, publish_pci_dev_cb publish_cb);
struct pci_dev *(*get)(struct xen_pcibk_device *pdev,
unsigned int domain, unsigned int bus,
unsigned int devfn);
};
extern const struct xen_pcibk_backend xen_pcibk_vpci_backend;
extern const struct xen_pcibk_backend xen_pcibk_passthrough_backend;
extern const struct xen_pcibk_backend *xen_pcibk_backend;
static inline int xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
struct pci_dev *dev,
int devid,
publish_pci_dev_cb publish_cb)
{
if (xen_pcibk_backend && xen_pcibk_backend->add)
return xen_pcibk_backend->add(pdev, dev, devid, publish_cb);
return -1;
}
static inline void xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
struct pci_dev *dev, bool lock)
{
if (xen_pcibk_backend && xen_pcibk_backend->release)
return xen_pcibk_backend->release(pdev, dev, lock);
}
static inline struct pci_dev *
xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev, unsigned int domain,
unsigned int bus, unsigned int devfn)
{
if (xen_pcibk_backend && xen_pcibk_backend->get)
return xen_pcibk_backend->get(pdev, domain, bus, devfn);
return NULL;
}
/**
* Add for domain0 PCIE-AER handling. Get guest domain/bus/devfn in xen_pcibk
* before sending aer request to pcifront, so that guest could identify
* device, coopearte with xen_pcibk to finish aer recovery job if device driver
* has the capability
*/
static inline int xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
struct xen_pcibk_device *pdev,
unsigned int *domain,
unsigned int *bus,
unsigned int *devfn)
{
if (xen_pcibk_backend && xen_pcibk_backend->find)
return xen_pcibk_backend->find(pcidev, pdev, domain, bus,
devfn);
return -1;
}
static inline int xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
{
if (xen_pcibk_backend && xen_pcibk_backend->init)
return xen_pcibk_backend->init(pdev);
return -1;
}
static inline int xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
publish_pci_root_cb cb)
{
if (xen_pcibk_backend && xen_pcibk_backend->publish)
return xen_pcibk_backend->publish(pdev, cb);
return -1;
}
static inline void xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
{
if (xen_pcibk_backend && xen_pcibk_backend->free)
return xen_pcibk_backend->free(pdev);
}
/* Handles events from front-end */
irqreturn_t xen_pcibk_handle_event(int irq, void *dev_id);
void xen_pcibk_do_op(struct work_struct *data);
int xen_pcibk_xenbus_register(void);
void xen_pcibk_xenbus_unregister(void);
extern int verbose_request;
void xen_pcibk_test_and_schedule_op(struct xen_pcibk_device *pdev);
#endif
/* Handles shared IRQs that can to device domain and control domain. */
void xen_pcibk_irq_handler(struct pci_dev *dev, int reset);
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