[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] common/device_tree: Add rwlock for dt_host
commit b8de00ff7a4bbf7a9fd480d6d7db458db3020f6d Author: Vikram Garhwal <vikram.garhwal@xxxxxxx> AuthorDate: Tue Sep 5 18:16:24 2023 -0700 Commit: Stefano Stabellini <stefano.stabellini@xxxxxxx> CommitDate: Tue Sep 5 18:33:58 2023 -0700 common/device_tree: Add rwlock for dt_host Dynamic programming ops will modify the dt_host and there might be other functions which are browsing the dt_host at the same time. To avoid the race conditions, adding rwlock for browsing the dt_host during runtime. dt_host writer will be added in the follow-up patch for device tree overlay functionalities. Reason behind adding rwlock instead of spinlock: For now, dynamic programming is the sole modifier of dt_host in Xen during run time. All other access functions like iommu_release_dt_device() are just reading the dt_host during run-time. So, there is a need to protect others from browsing the dt_host while dynamic programming is modifying it. rwlock is better suitable for this task as spinlock won't be able to differentiate between read and write access. Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> --- xen/common/device_tree.c | 1 + xen/drivers/passthrough/device_tree.c | 28 ++++++++++++++++++++++++++-- xen/include/xen/device_tree.h | 7 +++++++ 3 files changed, 34 insertions(+), 2 deletions(-) diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c index f38f51ec0b..b1c2952951 100644 --- a/xen/common/device_tree.c +++ b/xen/common/device_tree.c @@ -31,6 +31,7 @@ dt_irq_xlate_func dt_irq_xlate; struct dt_device_node *dt_host; /* Interrupt controller node*/ const struct dt_device_node *dt_interrupt_controller; +DEFINE_RWLOCK(dt_host_lock); /** * struct dt_alias_prop - Alias property in 'aliases' node diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c index 80f6efc606..075fb25a37 100644 --- a/xen/drivers/passthrough/device_tree.c +++ b/xen/drivers/passthrough/device_tree.c @@ -31,6 +31,8 @@ int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev) int rc = -EBUSY; struct domain_iommu *hd = dom_iommu(d); + ASSERT(system_state < SYS_STATE_active || rw_is_locked(&dt_host_lock)); + if ( !is_iommu_enabled(d) ) return -EINVAL; @@ -62,6 +64,8 @@ int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev) const struct domain_iommu *hd = dom_iommu(d); int rc; + ASSERT(rw_is_locked(&dt_host_lock)); + if ( !is_iommu_enabled(d) ) return -EINVAL; @@ -113,6 +117,8 @@ int iommu_release_dt_devices(struct domain *d) if ( !is_iommu_enabled(d) ) return 0; + read_lock(&dt_host_lock); + list_for_each_entry_safe(dev, _dev, &hd->dt_devices, domain_list) { rc = iommu_deassign_dt_device(d, dev); @@ -120,10 +126,14 @@ int iommu_release_dt_devices(struct domain *d) { dprintk(XENLOG_ERR, "Failed to deassign %s in domain %u\n", dt_node_full_name(dev), d->domain_id); + read_unlock(&dt_host_lock); + return rc; } } + read_unlock(&dt_host_lock); + return 0; } @@ -133,6 +143,8 @@ int iommu_remove_dt_device(struct dt_device_node *np) struct device *dev = dt_to_dev(np); int rc; + ASSERT(rw_is_locked(&dt_host_lock)); + if ( !iommu_enabled ) return 1; @@ -177,6 +189,8 @@ int iommu_add_dt_device(struct dt_device_node *np) struct device *dev = dt_to_dev(np); int rc = 1, index = 0; + ASSERT(system_state < SYS_STATE_active || rw_is_locked(&dt_host_lock)); + if ( !iommu_enabled ) return 1; @@ -249,6 +263,8 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, int ret; struct dt_device_node *dev; + read_lock(&dt_host_lock); + switch ( domctl->cmd ) { case XEN_DOMCTL_assign_device: @@ -289,7 +305,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, } if ( d == dom_io ) - return -EINVAL; + { + ret = -EINVAL; + break; + } ret = iommu_add_dt_device(dev); if ( ret < 0 ) @@ -327,7 +346,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, break; if ( d == dom_io ) - return -EINVAL; + { + ret = -EINVAL; + break; + } ret = iommu_deassign_dt_device(d, dev); @@ -342,5 +364,7 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, break; } + read_unlock(&dt_host_lock); + return ret; } diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h index 44d315c8ba..a262bba2ed 100644 --- a/xen/include/xen/device_tree.h +++ b/xen/include/xen/device_tree.h @@ -18,6 +18,7 @@ #include <xen/string.h> #include <xen/types.h> #include <xen/list.h> +#include <xen/rwlock.h> #define DEVICE_TREE_MAX_DEPTH 16 @@ -218,6 +219,12 @@ extern struct dt_device_node *dt_host; */ extern const struct dt_device_node *dt_interrupt_controller; +/* + * Lock that protects r/w updates to unflattened device tree i.e. dt_host during + * runtime. Lock may not be taken for boot only code. + */ +extern rwlock_t dt_host_lock; + /** * Find the interrupt controller * For the moment we handle only one interrupt controller: the first -- generated by git-patchbot for /home/xen/git/xen.git#master
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