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From:   Cornelia Huck <cohuck@redhat.com>
To:     Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>, kvm@vger.kernel.org
Cc:     David Hildenbrand <david@redhat.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Thomas Huth <thuth@redhat.com>, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org, Cornelia Huck <cohuck@redhat.com>
Subject: [PATCH] KVM: s390: improve documentation for S390_MEM_OP
Date:   Thu, 29 Aug 2019 14:47:46 +0200
Message-Id: <20190829124746.28665-1-cohuck@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Explicitly specify the valid ranges for size and ar, and reword
buf requirements a bit.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
---
supposed to go on top of "KVM: s390: Test for bad access register and
size at the start of S390_MEM_OP" (<20190829122517.31042-1-thuth@redhat.com>)
---
 Documentation/virt/kvm/api.txt | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 2d067767b617..76c9d6fdbfdb 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -3079,12 +3079,14 @@ This exception is also raised directly at the corresponding VCPU if the
 flag KVM_S390_MEMOP_F_INJECT_EXCEPTION is set in the "flags" field.
 
 The start address of the memory region has to be specified in the "gaddr"
-field, and the length of the region in the "size" field. "buf" is the buffer
-supplied by the userspace application where the read data should be written
-to for KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written
-is stored for a KVM_S390_MEMOP_LOGICAL_WRITE. "buf" is unused and can be NULL
-when KVM_S390_MEMOP_F_CHECK_ONLY is specified. "ar" designates the access
-register number to be used.
+field, and the length of the region in the "size" field (which must not
+be 0). The maximum value for "size" can be obtained by checking the
+KVM_CAP_S390_MEM_OP capability. "buf" is the buffer supplied by the
+userspace application where the read data should be written to for
+KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written is
+stored for a KVM_S390_MEMOP_LOGICAL_WRITE. When KVM_S390_MEMOP_F_CHECK_ONLY
+is specified, "buf" is unused and can be NULL. "ar" designates the access
+register number to be used; the valid range is 0..15.
 
 The "reserved" field is meant for future extensions. It is not used by
 KVM with the currently defined set of flags.
-- 
2.20.1