[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] IOMMU/x86: support freeing of pagetables
commit 5a991ad8a5caec0f085c1a8d931b67faff498868 Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Mon Jul 25 15:33:34 2022 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Mon Jul 25 15:33:34 2022 +0200 IOMMU/x86: support freeing of pagetables For vendor specific code to support superpages we need to be able to deal with a superpage mapping replacing an intermediate page table (or hierarchy thereof). Consequently an iommu_alloc_pgtable() counterpart is needed to free individual page tables while a domain is still alive. Since the freeing needs to be deferred until after a suitable IOTLB flush was performed, released page tables get queued for processing by a tasklet. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> Reviewed-by: Paul Durrant <paul@xxxxxxx> --- xen/arch/x86/include/asm/iommu.h | 1 + xen/drivers/passthrough/x86/iommu.c | 100 ++++++++++++++++++++++++++++++++++++ 2 files changed, 101 insertions(+) diff --git a/xen/arch/x86/include/asm/iommu.h b/xen/arch/x86/include/asm/iommu.h index 9ccf4f8bdd..a80dfb2d7f 100644 --- a/xen/arch/x86/include/asm/iommu.h +++ b/xen/arch/x86/include/asm/iommu.h @@ -147,6 +147,7 @@ void iommu_free_domid(domid_t domid, unsigned long *map); int __must_check iommu_free_pgtables(struct domain *d); struct domain_iommu; struct page_info *__must_check iommu_alloc_pgtable(struct domain_iommu *hd); +void iommu_queue_free_pgtable(struct domain_iommu *hd, struct page_info *pg); #endif /* !__ARCH_X86_IOMMU_H__ */ /* diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index be7617b1eb..8ac4044c08 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -12,6 +12,7 @@ * this program; If not, see <http://www.gnu.org/licenses/>. */ +#include <xen/cpu.h> #include <xen/sched.h> #include <xen/iocap.h> #include <xen/iommu.h> @@ -556,6 +557,105 @@ struct page_info *iommu_alloc_pgtable(struct domain_iommu *hd) return pg; } +/* + * Intermediate page tables which get replaced by large pages may only be + * freed after a suitable IOTLB flush. Hence such pages get queued on a + * per-CPU list, with a per-CPU tasklet processing the list on the assumption + * that the necessary IOTLB flush will have occurred by the time tasklets get + * to run. (List and tasklet being per-CPU has the benefit of accesses not + * requiring any locking.) + */ +static DEFINE_PER_CPU(struct page_list_head, free_pgt_list); +static DEFINE_PER_CPU(struct tasklet, free_pgt_tasklet); + +static void cf_check free_queued_pgtables(void *arg) +{ + struct page_list_head *list = arg; + struct page_info *pg; + unsigned int done = 0; + + ASSERT(list == &this_cpu(free_pgt_list)); + + while ( (pg = page_list_remove_head(list)) ) + { + free_domheap_page(pg); + + /* + * Just to be on the safe side, check for processing softirqs every + * once in a while. Generally it is expected that parties queuing + * pages for freeing will find a need for preemption before too many + * pages can be queued. Granularity of checking is somewhat arbitrary. + */ + if ( !(++done & 0x1ff) ) + process_pending_softirqs(); + } +} + +void iommu_queue_free_pgtable(struct domain_iommu *hd, struct page_info *pg) +{ + unsigned int cpu = smp_processor_id(); + + spin_lock(&hd->arch.pgtables.lock); + page_list_del(pg, &hd->arch.pgtables.list); + spin_unlock(&hd->arch.pgtables.lock); + + page_list_add_tail(pg, &per_cpu(free_pgt_list, cpu)); + + tasklet_schedule(&per_cpu(free_pgt_tasklet, cpu)); +} + +static int cf_check cpu_callback( + struct notifier_block *nfb, unsigned long action, void *hcpu) +{ + unsigned int cpu = (unsigned long)hcpu; + struct page_list_head *list = &per_cpu(free_pgt_list, cpu); + struct tasklet *tasklet = &per_cpu(free_pgt_tasklet, cpu); + + switch ( action ) + { + case CPU_DOWN_PREPARE: + tasklet_kill(tasklet); + break; + + case CPU_DEAD: + if ( !page_list_empty(list) ) + { + page_list_splice(list, &this_cpu(free_pgt_list)); + INIT_PAGE_LIST_HEAD(list); + tasklet_schedule(&this_cpu(free_pgt_tasklet)); + } + break; + + case CPU_UP_PREPARE: + INIT_PAGE_LIST_HEAD(list); + fallthrough; + case CPU_DOWN_FAILED: + tasklet_init(tasklet, free_queued_pgtables, list); + if ( !page_list_empty(list) ) + tasklet_schedule(tasklet); + break; + } + + return NOTIFY_DONE; +} + +static struct notifier_block cpu_nfb = { + .notifier_call = cpu_callback, +}; + +static int __init cf_check bsp_init(void) +{ + if ( iommu_enabled ) + { + cpu_callback(&cpu_nfb, CPU_UP_PREPARE, + (void *)(unsigned long)smp_processor_id()); + register_cpu_notifier(&cpu_nfb); + } + + return 0; +} +presmp_initcall(bsp_init); + bool arch_iommu_use_permitted(const struct domain *d) { /* -- generated by git-patchbot for /home/xen/git/xen.git#master
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