From 32ae4a2992529e2c7934e422035fad1d9b0f1fb5 Mon Sep 17 00:00:00 2001 From: Peter Oberparleiter Date: Fri, 31 Jan 2025 12:02:55 +0100 Subject: [PATCH] s390/cio: Fix CHPID "configure" attribute caching In some environments, the SCLP firmware interface used to query a CHPID's configured state is not supported. On these environments, rapidly reading the corresponding sysfs attribute produces inconsistent results: $ cat /sys/devices/css0/chp0.00/configure cat: /sys/devices/css0/chp0.00/configure: Operation not supported $ cat /sys/devices/css0/chp0.00/configure 3 This occurs for example when Linux is run as a KVM guest. The inconsistency is a result of CIO using cached results for generating the value of the "configure" attribute while failing to handle the situation where no data was returned by SCLP. Fix this by not updating the cache-expiration timestamp when SCLP returns no data. With the fix applied, the system response is consistent: $ cat /sys/devices/css0/chp0.00/configure cat: /sys/devices/css0/chp0.00/configure: Operation not supported $ cat /sys/devices/css0/chp0.00/configure cat: /sys/devices/css0/chp0.00/configure: Operation not supported Reviewed-by: Vineeth Vijayan Reviewed-by: Eric Farman Tested-by: Eric Farman Signed-off-by: Peter Oberparleiter Signed-off-by: Vasily Gorbik --- drivers/s390/cio/chp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/s390/cio/chp.c b/drivers/s390/cio/chp.c index 4a0b3f19bd8e..4f01b1929240 100644 --- a/drivers/s390/cio/chp.c +++ b/drivers/s390/cio/chp.c @@ -695,7 +695,8 @@ static int info_update(void) if (time_after(jiffies, chp_info_expires)) { /* Data is too old, update. */ rc = sclp_chp_read_info(&chp_info); - chp_info_expires = jiffies + CHP_INFO_UPDATE_INTERVAL ; + if (!rc) + chp_info_expires = jiffies + CHP_INFO_UPDATE_INTERVAL; } mutex_unlock(&info_lock);