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iommu/vt-d: Use RCU to protect global resources in interrupt context
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Global DMA and interrupt remapping resources may be accessed in
interrupt context, so use RCU instead of rwsem to protect them
in such cases.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
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Jiang Liu authored and Joerg Roedel committed Mar 4, 2014
1 parent 3a5670e commit 0e24261
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Showing 3 changed files with 53 additions and 23 deletions.
33 changes: 20 additions & 13 deletions drivers/iommu/dmar.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -71,13 +71,13 @@ static void __init dmar_register_drhd_unit(struct dmar_drhd_unit *drhd)
* the very end.
*/
if (drhd->include_all)
list_add_tail(&drhd->list, &dmar_drhd_units);
list_add_tail_rcu(&drhd->list, &dmar_drhd_units);
else
list_add(&drhd->list, &dmar_drhd_units);
list_add_rcu(&drhd->list, &dmar_drhd_units);
}

static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
struct pci_dev **dev, u16 segment)
struct pci_dev __rcu **dev, u16 segment)
{
struct pci_bus *bus;
struct pci_dev *pdev = NULL;
Expand Down Expand Up @@ -122,7 +122,9 @@ static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
pci_name(pdev));
return -EINVAL;
}
*dev = pdev;

rcu_assign_pointer(*dev, pdev);

return 0;
}

Expand All @@ -149,7 +151,7 @@ void *dmar_alloc_dev_scope(void *start, void *end, int *cnt)
}

int __init dmar_parse_dev_scope(void *start, void *end, int *cnt,
struct pci_dev ***devices, u16 segment)
struct pci_dev __rcu ***devices, u16 segment)
{
struct acpi_dmar_device_scope *scope;
int index, ret;
Expand Down Expand Up @@ -177,7 +179,7 @@ int __init dmar_parse_dev_scope(void *start, void *end, int *cnt,
return 0;
}

void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt)
void dmar_free_dev_scope(struct pci_dev __rcu ***devices, int *cnt)
{
int i;
struct pci_dev *tmp_dev;
Expand All @@ -186,9 +188,10 @@ void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt)
for_each_active_dev_scope(*devices, *cnt, i, tmp_dev)
pci_dev_put(tmp_dev);
kfree(*devices);
*devices = NULL;
*cnt = 0;
}

*devices = NULL;
*cnt = 0;
}

/**
Expand Down Expand Up @@ -410,7 +413,7 @@ parse_dmar_table(void)
return ret;
}

static int dmar_pci_device_match(struct pci_dev *devices[], int cnt,
static int dmar_pci_device_match(struct pci_dev __rcu *devices[], int cnt,
struct pci_dev *dev)
{
int index;
Expand All @@ -431,26 +434,30 @@ static int dmar_pci_device_match(struct pci_dev *devices[], int cnt,
struct dmar_drhd_unit *
dmar_find_matched_drhd_unit(struct pci_dev *dev)
{
struct dmar_drhd_unit *dmaru = NULL;
struct dmar_drhd_unit *dmaru;
struct acpi_dmar_hardware_unit *drhd;

dev = pci_physfn(dev);

rcu_read_lock();
for_each_drhd_unit(dmaru) {
drhd = container_of(dmaru->hdr,
struct acpi_dmar_hardware_unit,
header);

if (dmaru->include_all &&
drhd->segment == pci_domain_nr(dev->bus))
return dmaru;
goto out;

if (dmar_pci_device_match(dmaru->devices,
dmaru->devices_cnt, dev))
return dmaru;
goto out;
}
dmaru = NULL;
out:
rcu_read_unlock();

return NULL;
return dmaru;
}

int __init dmar_dev_scope_init(void)
Expand Down
20 changes: 16 additions & 4 deletions drivers/iommu/intel-iommu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -385,14 +385,14 @@ struct dmar_rmrr_unit {
struct acpi_dmar_header *hdr; /* ACPI header */
u64 base_address; /* reserved base address*/
u64 end_address; /* reserved end address */
struct pci_dev **devices; /* target devices */
struct pci_dev __rcu **devices; /* target devices */
int devices_cnt; /* target device count */
};

struct dmar_atsr_unit {
struct list_head list; /* list of ATSR units */
struct acpi_dmar_header *hdr; /* ACPI header */
struct pci_dev **devices; /* target devices */
struct pci_dev __rcu **devices; /* target devices */
int devices_cnt; /* target device count */
u8 include_all:1; /* include all ports */
};
Expand Down Expand Up @@ -634,12 +634,15 @@ static void domain_update_iommu_superpage(struct dmar_domain *domain)
}

/* set iommu_superpage to the smallest common denominator */
rcu_read_lock();
for_each_active_iommu(iommu, drhd) {
mask &= cap_super_page_val(iommu->cap);
if (!mask) {
break;
}
}
rcu_read_unlock();

domain->iommu_superpage = fls(mask);
}

Expand All @@ -658,6 +661,7 @@ static struct intel_iommu *device_to_iommu(int segment, u8 bus, u8 devfn)
struct pci_dev *dev;
int i;

rcu_read_lock();
for_each_active_iommu(iommu, drhd) {
if (segment != drhd->segment)
continue;
Expand All @@ -677,6 +681,7 @@ static struct intel_iommu *device_to_iommu(int segment, u8 bus, u8 devfn)
}
iommu = NULL;
out:
rcu_read_unlock();

return iommu;
}
Expand Down Expand Up @@ -1535,10 +1540,12 @@ static void domain_exit(struct dmar_domain *domain)
dma_pte_free_pagetable(domain, 0, DOMAIN_MAX_PFN(domain->gaw));

/* clear attached or cached domains */
rcu_read_lock();
for_each_active_iommu(iommu, drhd)
if (domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE ||
test_bit(iommu->seq_id, domain->iommu_bmp))
iommu_detach_domain(domain, iommu);
rcu_read_unlock();

free_domain_mem(domain);
}
Expand Down Expand Up @@ -2338,6 +2345,7 @@ static bool device_has_rmrr(struct pci_dev *dev)
struct pci_dev *tmp;
int i;

rcu_read_lock();
for_each_rmrr_units(rmrr) {
/*
* Return TRUE if this RMRR contains the device that
Expand All @@ -2346,9 +2354,11 @@ static bool device_has_rmrr(struct pci_dev *dev)
for_each_active_dev_scope(rmrr->devices,
rmrr->devices_cnt, i, tmp)
if (tmp == dev) {
rcu_read_unlock();
return true;
}
}
rcu_read_unlock();
return false;
}

Expand Down Expand Up @@ -3512,7 +3522,7 @@ int __init dmar_parse_one_atsr(struct acpi_dmar_header *hdr)
atsru->hdr = hdr;
atsru->include_all = atsr->flags & 0x1;

list_add(&atsru->list, &dmar_atsr_units);
list_add_rcu(&atsru->list, &dmar_atsr_units);

return 0;
}
Expand Down Expand Up @@ -3574,6 +3584,7 @@ int dmar_find_matched_atsr_unit(struct pci_dev *dev)
if (!bridge)
return 0;

rcu_read_lock();
list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) {
atsr = container_of(atsru->hdr, struct acpi_dmar_atsr, header);
if (atsr->segment != pci_domain_nr(dev->bus))
Expand All @@ -3588,6 +3599,7 @@ int dmar_find_matched_atsr_unit(struct pci_dev *dev)
}
ret = 0;
out:
rcu_read_unlock();

return ret;
}
Expand All @@ -3604,7 +3616,7 @@ int __init dmar_parse_rmrr_atsr_dev(void)
return ret;
}

list_for_each_entry(atsr, &dmar_atsr_units, list) {
list_for_each_entry_rcu(atsr, &dmar_atsr_units, list) {
ret = atsr_parse_dev(atsr);
if (ret)
return ret;
Expand Down
23 changes: 17 additions & 6 deletions include/linux/dmar.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
#include <linux/msi.h>
#include <linux/irqreturn.h>
#include <linux/rwsem.h>
#include <linux/rcupdate.h>

struct acpi_dmar_header;

Expand All @@ -41,7 +42,7 @@ struct dmar_drhd_unit {
struct list_head list; /* list of drhd units */
struct acpi_dmar_header *hdr; /* ACPI header */
u64 reg_base_addr; /* register base address*/
struct pci_dev **devices; /* target device array */
struct pci_dev __rcu **devices;/* target device array */
int devices_cnt; /* target device count */
u16 segment; /* PCI domain */
u8 ignored:1; /* ignore drhd */
Expand All @@ -53,22 +54,31 @@ extern struct rw_semaphore dmar_global_lock;
extern struct list_head dmar_drhd_units;

#define for_each_drhd_unit(drhd) \
list_for_each_entry(drhd, &dmar_drhd_units, list)
list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)

#define for_each_active_drhd_unit(drhd) \
list_for_each_entry(drhd, &dmar_drhd_units, list) \
list_for_each_entry_rcu(drhd, &dmar_drhd_units, list) \
if (drhd->ignored) {} else

#define for_each_active_iommu(i, drhd) \
list_for_each_entry(drhd, &dmar_drhd_units, list) \
list_for_each_entry_rcu(drhd, &dmar_drhd_units, list) \
if (i=drhd->iommu, drhd->ignored) {} else

#define for_each_iommu(i, drhd) \
list_for_each_entry(drhd, &dmar_drhd_units, list) \
list_for_each_entry_rcu(drhd, &dmar_drhd_units, list) \
if (i=drhd->iommu, 0) {} else

static inline bool dmar_rcu_check(void)
{
return rwsem_is_locked(&dmar_global_lock) ||
system_state == SYSTEM_BOOTING;
}

#define dmar_rcu_dereference(p) rcu_dereference_check((p), dmar_rcu_check())

#define for_each_dev_scope(a, c, p, d) \
for ((p) = 0; ((d) = (p) < (c) ? (a)[(p)] : NULL, (p) < (c)); (p)++)
for ((p) = 0; ((d) = (p) < (c) ? dmar_rcu_dereference((a)[(p)]) : \
NULL, (p) < (c)); (p)++)

#define for_each_active_dev_scope(a, c, p, d) \
for_each_dev_scope((a), (c), (p), (d)) if (!(d)) { continue; } else
Expand All @@ -78,6 +88,7 @@ extern int dmar_dev_scope_init(void);
extern int dmar_parse_dev_scope(void *start, void *end, int *cnt,
struct pci_dev ***devices, u16 segment);
extern void *dmar_alloc_dev_scope(void *start, void *end, int *cnt);
extern void dmar_free_dev_scope(struct pci_dev __rcu ***devices, int *cnt);
extern void dmar_free_dev_scope(struct pci_dev ***devices, int *cnt);

/* Intel IOMMU detection */
Expand Down

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