linux-kernel - [PATCH v2] doc: kvm: Fix return description of KVM_SET

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Date:   Wed,  4 Sep 2019 14:01:18 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] doc: kvm: Fix return description of KVM_SET_MSRS

Userspace can use ioctl KVM_SET_MSRS to update a set of MSRs of guest.
This ioctl sets specified MSRs one by one. Once it fails to set an MSR
due to setting reserved bits, the MSR is not supported/emulated by kvm,
or violating other restrictions, it stops further processing and returns
the number of MSRs have been set successfully.

Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---
v2:
  elaborate the changelog and description of ioctl KVM_SET_MSRS based on
  Sean's comments.

---
 Documentation/virt/kvm/api.txt | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 2d067767b617..4638e893dec0 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -586,7 +586,7 @@ Capability: basic
 Architectures: x86
 Type: vcpu ioctl
 Parameters: struct kvm_msrs (in)
-Returns: 0 on success, -1 on error
+Returns: number of msrs successfully set (see below), -1 on error
 
 Writes model-specific registers to the vcpu.  See KVM_GET_MSRS for the
 data structures.
@@ -595,6 +595,11 @@ Application code should set the 'nmsrs' member (which indicates the
 size of the entries array), and the 'index' and 'data' members of each
 array entry.
 
+It tries to set the MSRs in array entries[] one by one. Once failing to
+set an MSR (due to setting reserved bits, the MSR is not supported/emulated
+by kvm, or violating other restrctions), it stops setting following MSRs
+and returns the number of MSRs have been set successfully.
+
 
 4.20 KVM_SET_CPUID
 
-- 
2.19.1