[PATCH 7/7] CXL: Unmap MMIO regions when detaching a context

[Ian Munsie]

This one should go to stable - this was the first bug uncovered after
fixing the sleep while atomic and force unbinding the driver.

Cheers,
-Ian

Excerpts from Ian Munsie's message of 2014-12-08 19:18:01 +1100:
> From: Ian Munsie <imunsie at au1.ibm.com>
> 
> If we need to force detach a context (e.g. due to EEH or simply force
> unbinding the driver) we should prevent the userspace contexts from
> being able to access the Problem State Area MMIO region further, which
> they may have mapped with mmap().
> 
> This patch unmaps any mapped MMIO regions when detaching a userspace
> context.
> 
> Signed-off-by: Ian Munsie <imunsie at au1.ibm.com>
> ---
>  drivers/misc/cxl/context.c | 11 ++++++++++-
>  drivers/misc/cxl/cxl.h     |  7 ++++++-
>  drivers/misc/cxl/file.c    |  6 +++++-
>  3 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
> index 4aa31a3..51fd6b5 100644
> --- a/drivers/misc/cxl/context.c
> +++ b/drivers/misc/cxl/context.c
> @@ -34,7 +34,8 @@ struct cxl_context *cxl_context_alloc(void)
>  /*
>   * Initialises a CXL context.
>   */
> -int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master)
> +int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
> +             struct address_space *mapping)
>  {
>      int i;
>  
> @@ -42,6 +43,8 @@ int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master)
>      ctx->afu = afu;
>      ctx->master = master;
>      ctx->pid = NULL; /* Set in start work ioctl */
> +    mutex_init(&ctx->mapping_lock);
> +    ctx->mapping = mapping;
>  
>      /*
>       * Allocate the segment table before we put it in the IDR so that we
> @@ -147,6 +150,12 @@ static void __detach_context(struct cxl_context *ctx)
>      afu_release_irqs(ctx);
>      flush_work(&ctx->fault_work); /* Only needed for dedicated process */
>      wake_up_all(&ctx->wq);
> +
> +    /* Release Problem State Area mapping */
> +    mutex_lock(&ctx->mapping_lock);
> +    if (ctx->mapping)
> +        unmap_mapping_range(ctx->mapping, 0, 0, 1);
> +    mutex_unlock(&ctx->mapping_lock);
>  }
>  
>  /*
> diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
> index c1f8aa6..0df0438 100644
> --- a/drivers/misc/cxl/cxl.h
> +++ b/drivers/misc/cxl/cxl.h
> @@ -405,6 +405,10 @@ struct cxl_context {
>      phys_addr_t psn_phys;
>      u64 psn_size;
>  
> +    /* Used to unmap any mmaps when force detaching */
> +    struct address_space *mapping;
> +    struct mutex mapping_lock;
> +
>      spinlock_t sste_lock; /* Protects segment table entries */
>      struct cxl_sste *sstp;
>      u64 sstp0, sstp1;
> @@ -606,7 +610,8 @@ int cxl_alloc_sst(struct cxl_context *ctx);
>  void init_cxl_native(void);
>  
>  struct cxl_context *cxl_context_alloc(void);
> -int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master);
> +int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
> +             struct address_space *mapping);
>  void cxl_context_free(struct cxl_context *ctx);
>  int cxl_context_iomap(struct cxl_context *ctx, struct vm_area_struct *vma);
>  
> diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
> index 2e067a5..b09be44 100644
> --- a/drivers/misc/cxl/file.c
> +++ b/drivers/misc/cxl/file.c
> @@ -77,7 +77,7 @@ static int __afu_open(struct inode *inode, struct file *file, bool master)
>          goto err_put_afu;
>      }
>  
> -    if ((rc = cxl_context_init(ctx, afu, master)))
> +    if ((rc = cxl_context_init(ctx, afu, master, inode->i_mapping)))
>          goto err_put_afu;
>  
>      pr_devel("afu_open pe: %i\n", ctx->pe);
> @@ -113,6 +113,10 @@ static int afu_release(struct inode *inode, struct file *file)
>           __func__, ctx->pe);
>      cxl_context_detach(ctx);
>  
> +    mutex_lock(&ctx->mapping_lock);
> +    ctx->mapping = NULL;
> +    mutex_unlock(&ctx->mapping_lock);
> +
>      put_device(&ctx->afu->dev);
>  
>      /*