linux-kernel - [PATCH 1/2] s390: uv: Fix sysfs max number of VCPUs reporting

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Date:   Tue, 19 Jan 2021 05:04:01 -0500
From:   Janosch Frank <frankja@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, thuth@...hat.com, david@...hat.com,
        borntraeger@...ibm.com, imbrenda@...ux.ibm.com, cohuck@...hat.com,
        linux-s390@...r.kernel.org, gor@...ux.ibm.com,
        mihajlov@...ux.ibm.com
Subject: [PATCH 1/2] s390: uv: Fix sysfs max number of VCPUs reporting

The number reported by the query is N-1 and I think people reading the
sysfs file would expect N instead. For users creating VMs there's no
actual difference because KVM's limit is currently below the UV's
limit.

The naming of the field is a bit misleading. Number in this context is
used like ID and starts at 0. The query field denotes the maximum
number that can be put into the VCPU number field in the "create
secure CPU" UV call.

Signed-off-by: Janosch Frank <frankja@...ux.ibm.com>
Fixes: a0f60f8431999 ("s390/protvirt: Add sysfs firmware interface for Ultravisor information")
Cc: stable@...r.kernel.org
---
 arch/s390/boot/uv.c        | 2 +-
 arch/s390/include/asm/uv.h | 4 ++--
 arch/s390/kernel/uv.c      | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/s390/boot/uv.c b/arch/s390/boot/uv.c
index a15c033f53ca..afb721082989 100644
--- a/arch/s390/boot/uv.c
+++ b/arch/s390/boot/uv.c
@@ -35,7 +35,7 @@ void uv_query_info(void)
 		uv_info.guest_cpu_stor_len = uvcb.cpu_stor_len;
 		uv_info.max_sec_stor_addr = ALIGN(uvcb.max_guest_stor_addr, PAGE_SIZE);
 		uv_info.max_num_sec_conf = uvcb.max_num_sec_conf;
-		uv_info.max_guest_cpus = uvcb.max_guest_cpus;
+		uv_info.max_guest_cpu_id = uvcb.max_guest_cpu_num;
 	}
 
 #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 0325fc0469b7..c484c95ea142 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -96,7 +96,7 @@ struct uv_cb_qui {
 	u32 max_num_sec_conf;
 	u64 max_guest_stor_addr;
 	u8  reserved88[158 - 136];
-	u16 max_guest_cpus;
+	u16 max_guest_cpu_num;
 	u8  reserveda0[200 - 160];
 } __packed __aligned(8);
 
@@ -273,7 +273,7 @@ struct uv_info {
 	unsigned long guest_cpu_stor_len;
 	unsigned long max_sec_stor_addr;
 	unsigned int max_num_sec_conf;
-	unsigned short max_guest_cpus;
+	unsigned short max_guest_cpu_id;
 };
 
 extern struct uv_info uv_info;
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 883bfed9f5c2..b2d2ad153067 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -368,7 +368,7 @@ static ssize_t uv_query_max_guest_cpus(struct kobject *kobj,
 				       struct kobj_attribute *attr, char *page)
 {
 	return scnprintf(page, PAGE_SIZE, "%d\n",
-			uv_info.max_guest_cpus);
+			uv_info.max_guest_cpu_id + 1);
 }
 
 static struct kobj_attribute uv_query_max_guest_cpus_attr =
-- 
2.25.1