[PATCH 1/1] Drivers: hv: Notify the host of permanent hot-add failures

[PATCH 1/1] Drivers: hv: Notify the host of permanent hot-add failures

[K. Y. Srinivasan]

If memory hot-add fails with the error -EEXIST, then this is a permanent
failure. Notify the host 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.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_balloon.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 71655b4..d2ed673 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -583,6 +583,16 @@ 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;
@@ -842,11 +852,14 @@ static void hot_add_req(struct work_struct *dummy)
 		rg_sz = region_size;
 	}
 
-	resp.page_count = process_hot_add(pg_start, pfn_cnt,
-					rg_start, rg_sz);
+	if (do_hot_add)
+		resp.page_count = process_hot_add(pg_start, pfn_cnt,
+						rg_start, rg_sz);
 #endif
 	if (resp.page_count > 0)
 		resp.result = 1;
+	else if (!do_hot_add)
+		resp.result = 1;
 	else
 		resp.result = 0;
 
-- 
1.7.4.1

RE: [PATCH 1/1] Drivers: hv: Notify the host of permanent hot-add failures

[KY Srinivasan]

> -----Original Message-----
> From: K. Y. Srinivasan [mailto:kys@microsoft.com]
> Sent: Sunday, March 17, 2013 11:08 PM
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Cc: KY Srinivasan
> Subject: [PATCH 1/1] 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 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.

Greg,

Please drop this patch; I am going to resend this as part of the earlier balloon driver patches I had sent.

Regards,

K. Y
> 
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/hv/hv_balloon.c |   17 +++++++++++++++--
>  1 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index 71655b4..d2ed673 100644
> --- a/drivers/hv/hv_balloon.c
> +++ b/drivers/hv/hv_balloon.c
> @@ -583,6 +583,16 @@ 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;
> @@ -842,11 +852,14 @@ static void hot_add_req(struct work_struct *dummy)
>  		rg_sz = region_size;
>  	}
> 
> -	resp.page_count = process_hot_add(pg_start, pfn_cnt,
> -					rg_start, rg_sz);
> +	if (do_hot_add)
> +		resp.page_count = process_hot_add(pg_start, pfn_cnt,
> +						rg_start, rg_sz);
>  #endif
>  	if (resp.page_count > 0)
>  		resp.result = 1;
> +	else if (!do_hot_add)
> +		resp.result = 1;
>  	else
>  		resp.result = 0;
> 
> --
> 1.7.4.1
> 
>