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Commit 7f4f2302 authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
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Drivers: hv: Notify the host of permanent hot-add failures 



If memory hot-add fails with the error -EEXIST, then this is a permanent
failure. Notify the host of this information, so the host will not attempt
hot-add again. If the failure were a transient failure, host will attempt
a hot-add after some delay.

In this version of the patch, I have added some additional comments
to clarify how the host treats different failure conditions.

Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f766dc1e

drivers/hv/hv_balloon.c

+31 −2
Original line number Diff line number Diff line
@@ -590,6 +590,16 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size, 


		if (ret) {

			pr_info("hot_add memory failed error is %d\n", ret);

			if (ret == -EEXIST) {

				/*

				 * This error indicates that the error

				 * is not a transient failure. This is the

				 * case where the guest's physical address map

				 * precludes hot adding memory. Stop all further

				 * memory hot-add.

				 */

				do_hot_add = false;

			}

			has->ha_end_pfn -= HA_CHUNK;

			has->covered_end_pfn -=  processed_pfn;

			break;
@@ -849,11 +859,30 @@ static void hot_add_req(struct work_struct *dummy) 
		rg_sz = region_size;

	}



	if (do_hot_add)

		resp.page_count = process_hot_add(pg_start, pfn_cnt,

						rg_start, rg_sz);

#endif

	/*

	 * The result field of the response structure has the

	 * following semantics:

	 *

	 * 1. If all or some pages hot-added: Guest should return success.

	 *

	 * 2. If no pages could be hot-added:

	 *

	 * If the guest returns success, then the host

	 * will not attempt any further hot-add operations. This

	 * signifies a permanent failure.

	 *

	 * If the guest returns failure, then this failure will be

	 * treated as a transient failure and the host may retry the

	 * hot-add operation after some delay.

	 */

	if (resp.page_count > 0)

		resp.result = 1;

	else if (!do_hot_add)

		resp.result = 1;

	else

		resp.result = 0;