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![Vaibhav Jain](/assets/img/avatar_default.png)
Presently when a user-space process issues CXL_IOCTL_START_WORK ioctl we store the pid of the current task_struct and use it to get pointer to the mm_struct of the process, while processing page or segment faults from the capi card. However this causes issues when the thread that had originally issued the start-work ioctl exits in which case the stored pid is no more valid and the cxl driver is unable to handle faults as the mm_struct corresponding to process is no more accessible. This patch fixes this issue by using the mm_struct of the next alive task in the thread group. This is done by iterating over all the tasks in the thread group starting from thread group leader and calling get_task_mm on each one of them. When a valid mm_struct is obtained the pid of the associated task is stored in the context replacing the exiting one for handling future faults. The patch introduces a new function named get_mem_context that checks if the current task pointed to by ctx->pid is dead? If yes it performs the steps described above. Also a new variable cxl_context.glpid is introduced which stores the pid of the thread group leader associated with the context owning task. Reported-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com> Reported-by: Frank Haverkamp <HAVERKAM@de.ibm.com> Suggested-by: Ian Munsie <imunsie@au1.ibm.com> Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com> Acked-by: Ian Munsie <imunsie@au1.ibm.com> Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com> Reviewed-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
303 lines
7.6 KiB
C
303 lines
7.6 KiB
C
/*
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* Copyright 2014 IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/bitmap.h>
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#include <linux/sched.h>
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#include <linux/pid.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/debugfs.h>
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#include <linux/slab.h>
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#include <linux/idr.h>
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#include <asm/cputable.h>
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#include <asm/current.h>
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#include <asm/copro.h>
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#include "cxl.h"
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/*
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* Allocates space for a CXL context.
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*/
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struct cxl_context *cxl_context_alloc(void)
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{
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return kzalloc(sizeof(struct cxl_context), GFP_KERNEL);
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}
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/*
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* Initialises a CXL context.
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*/
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int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
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struct address_space *mapping)
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{
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int i;
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spin_lock_init(&ctx->sste_lock);
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ctx->afu = afu;
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ctx->master = master;
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ctx->pid = ctx->glpid = NULL; /* Set in start work ioctl */
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mutex_init(&ctx->mapping_lock);
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ctx->mapping = mapping;
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/*
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* Allocate the segment table before we put it in the IDR so that we
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* can always access it when dereferenced from IDR. For the same
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* reason, the segment table is only destroyed after the context is
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* removed from the IDR. Access to this in the IOCTL is protected by
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* Linux filesytem symantics (can't IOCTL until open is complete).
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*/
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i = cxl_alloc_sst(ctx);
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if (i)
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return i;
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INIT_WORK(&ctx->fault_work, cxl_handle_fault);
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init_waitqueue_head(&ctx->wq);
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spin_lock_init(&ctx->lock);
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ctx->irq_bitmap = NULL;
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ctx->pending_irq = false;
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ctx->pending_fault = false;
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ctx->pending_afu_err = false;
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/*
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* When we have to destroy all contexts in cxl_context_detach_all() we
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* end up with afu_release_irqs() called from inside a
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* idr_for_each_entry(). Hence we need to make sure that anything
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* dereferenced from this IDR is ok before we allocate the IDR here.
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* This clears out the IRQ ranges to ensure this.
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*/
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for (i = 0; i < CXL_IRQ_RANGES; i++)
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ctx->irqs.range[i] = 0;
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mutex_init(&ctx->status_mutex);
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ctx->status = OPENED;
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/*
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* Allocating IDR! We better make sure everything's setup that
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* dereferences from it.
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*/
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mutex_lock(&afu->contexts_lock);
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idr_preload(GFP_KERNEL);
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i = idr_alloc(&ctx->afu->contexts_idr, ctx, 0,
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ctx->afu->num_procs, GFP_NOWAIT);
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idr_preload_end();
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mutex_unlock(&afu->contexts_lock);
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if (i < 0)
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return i;
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ctx->pe = i;
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ctx->elem = &ctx->afu->spa[i];
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ctx->pe_inserted = false;
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/*
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* take a ref on the afu so that it stays alive at-least till
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* this context is reclaimed inside reclaim_ctx.
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*/
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cxl_afu_get(afu);
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return 0;
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}
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static int cxl_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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struct cxl_context *ctx = vma->vm_file->private_data;
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unsigned long address = (unsigned long)vmf->virtual_address;
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u64 area, offset;
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offset = vmf->pgoff << PAGE_SHIFT;
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pr_devel("%s: pe: %i address: 0x%lx offset: 0x%llx\n",
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__func__, ctx->pe, address, offset);
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if (ctx->afu->current_mode == CXL_MODE_DEDICATED) {
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area = ctx->afu->psn_phys;
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if (offset >= ctx->afu->adapter->ps_size)
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return VM_FAULT_SIGBUS;
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} else {
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area = ctx->psn_phys;
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if (offset >= ctx->psn_size)
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return VM_FAULT_SIGBUS;
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}
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mutex_lock(&ctx->status_mutex);
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if (ctx->status != STARTED) {
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mutex_unlock(&ctx->status_mutex);
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pr_devel("%s: Context not started, failing problem state access\n", __func__);
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if (ctx->mmio_err_ff) {
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if (!ctx->ff_page) {
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ctx->ff_page = alloc_page(GFP_USER);
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if (!ctx->ff_page)
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return VM_FAULT_OOM;
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memset(page_address(ctx->ff_page), 0xff, PAGE_SIZE);
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}
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get_page(ctx->ff_page);
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vmf->page = ctx->ff_page;
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vma->vm_page_prot = pgprot_cached(vma->vm_page_prot);
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return 0;
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}
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return VM_FAULT_SIGBUS;
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}
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vm_insert_pfn(vma, address, (area + offset) >> PAGE_SHIFT);
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mutex_unlock(&ctx->status_mutex);
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return VM_FAULT_NOPAGE;
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}
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static const struct vm_operations_struct cxl_mmap_vmops = {
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.fault = cxl_mmap_fault,
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};
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/*
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* Map a per-context mmio space into the given vma.
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*/
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int cxl_context_iomap(struct cxl_context *ctx, struct vm_area_struct *vma)
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{
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u64 start = vma->vm_pgoff << PAGE_SHIFT;
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u64 len = vma->vm_end - vma->vm_start;
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if (ctx->afu->current_mode == CXL_MODE_DEDICATED) {
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if (start + len > ctx->afu->adapter->ps_size)
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return -EINVAL;
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} else {
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if (start + len > ctx->psn_size)
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return -EINVAL;
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}
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if (ctx->afu->current_mode != CXL_MODE_DEDICATED) {
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/* make sure there is a valid per process space for this AFU */
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if ((ctx->master && !ctx->afu->psa) || (!ctx->afu->pp_psa)) {
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pr_devel("AFU doesn't support mmio space\n");
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return -EINVAL;
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}
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/* Can't mmap until the AFU is enabled */
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if (!ctx->afu->enabled)
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return -EBUSY;
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}
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pr_devel("%s: mmio physical: %llx pe: %i master:%i\n", __func__,
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ctx->psn_phys, ctx->pe , ctx->master);
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vma->vm_flags |= VM_IO | VM_PFNMAP;
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vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
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vma->vm_ops = &cxl_mmap_vmops;
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return 0;
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}
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/*
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* Detach a context from the hardware. This disables interrupts and doesn't
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* return until all outstanding interrupts for this context have completed. The
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* hardware should no longer access *ctx after this has returned.
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*/
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int __detach_context(struct cxl_context *ctx)
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{
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enum cxl_context_status status;
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mutex_lock(&ctx->status_mutex);
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status = ctx->status;
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ctx->status = CLOSED;
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mutex_unlock(&ctx->status_mutex);
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if (status != STARTED)
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return -EBUSY;
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/* Only warn if we detached while the link was OK.
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* If detach fails when hw is down, we don't care.
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*/
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WARN_ON(cxl_detach_process(ctx) &&
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cxl_adapter_link_ok(ctx->afu->adapter));
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flush_work(&ctx->fault_work); /* Only needed for dedicated process */
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/* release the reference to the group leader and mm handling pid */
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put_pid(ctx->pid);
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put_pid(ctx->glpid);
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cxl_ctx_put();
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return 0;
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}
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/*
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* Detach the given context from the AFU. This doesn't actually
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* free the context but it should stop the context running in hardware
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* (ie. prevent this context from generating any further interrupts
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* so that it can be freed).
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*/
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void cxl_context_detach(struct cxl_context *ctx)
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{
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int rc;
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rc = __detach_context(ctx);
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if (rc)
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return;
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afu_release_irqs(ctx, ctx);
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wake_up_all(&ctx->wq);
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}
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/*
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* Detach all contexts on the given AFU.
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*/
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void cxl_context_detach_all(struct cxl_afu *afu)
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{
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struct cxl_context *ctx;
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int tmp;
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mutex_lock(&afu->contexts_lock);
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idr_for_each_entry(&afu->contexts_idr, ctx, tmp) {
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/*
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* Anything done in here needs to be setup before the IDR is
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* created and torn down after the IDR removed
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*/
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cxl_context_detach(ctx);
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/*
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* We are force detaching - remove any active PSA mappings so
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* userspace cannot interfere with the card if it comes back.
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* Easiest way to exercise this is to unbind and rebind the
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* driver via sysfs while it is in use.
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*/
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mutex_lock(&ctx->mapping_lock);
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if (ctx->mapping)
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unmap_mapping_range(ctx->mapping, 0, 0, 1);
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mutex_unlock(&ctx->mapping_lock);
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}
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mutex_unlock(&afu->contexts_lock);
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}
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static void reclaim_ctx(struct rcu_head *rcu)
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{
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struct cxl_context *ctx = container_of(rcu, struct cxl_context, rcu);
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free_page((u64)ctx->sstp);
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if (ctx->ff_page)
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__free_page(ctx->ff_page);
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ctx->sstp = NULL;
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if (ctx->kernelapi)
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kfree(ctx->mapping);
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if (ctx->irq_bitmap)
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kfree(ctx->irq_bitmap);
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/* Drop ref to the afu device taken during cxl_context_init */
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cxl_afu_put(ctx->afu);
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kfree(ctx);
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}
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void cxl_context_free(struct cxl_context *ctx)
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{
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mutex_lock(&ctx->afu->contexts_lock);
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idr_remove(&ctx->afu->contexts_idr, ctx->pe);
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mutex_unlock(&ctx->afu->contexts_lock);
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call_rcu(&ctx->rcu, reclaim_ctx);
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}
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