Re: [PATCH v9 4/7] x86/sgx: Add SGX infrastructure to recover from poison

[Sean Christopherson <seanjc@google.com>]

On Mon, Oct 11, 2021, Tony Luck wrote:
> +	section = &sgx_epc_sections[page->section];
> +	node = section->node;
> +
> +	spin_lock(&node->lock);
> +
> +	/* Already poisoned? Nothing more to do */
> +	if (page->poison)
> +		goto out;
> +
> +	page->poison = 1;
> +
> +	/*
> +	 * If flags is zero, then the page is on a free list.
> +	 * Move it to the poison page list.
> +	 */
> +	if (!page->flags) {

If the flag is inverted, this becomes

	if (page->flags & SGX_EPC_PAGE_FREE) {

> +		list_del(&page->list);
> +		list_add(&page->list, &sgx_poison_page_list);

list_move(), and needs the same protection for sgx_poison_page_list.

> +		goto out;
> +	}
> +
> +	/*
> +	 * TBD: Add additional plumbing to enable pre-emptive
> +	 * action for asynchronous poison notification. Until
> +	 * then just hope that the poison:
> +	 * a) is not accessed - sgx_free_epc_page() will deal with it
> +	 *    when the user gives it back
> +	 * b) results in a recoverable machine check rather than
> +	 *    a fatal one
> +	 */
> +out:
> +	spin_unlock(&node->lock);
> +	return 0;
> +}
> +
>  /**
>   * A section metric is concatenated in a way that @low bits 12-31 define the
>   * bits 12-31 of the metric and @high bits 0-19 define the bits 32-51 of the
> 
> -- 
> 2.31.1
>