From 8c850d9e3acb7b52bb98a31f13be28f861aaadfa Mon Sep 17 00:00:00 2001
From: Jia He <justin.he@arm.com>
Date: Mon, 23 Mar 2020 13:20:00 +0800
Subject: [PATCH] config: Add scsi_mod.scan=none for virtio-scsi

As per [1], the default scan mode of scsi is sync.
kata-agent already scans the SCSI buses [2], changing it to none
can reduce the guest boot time.

=Before this patch=
[    0.113828] [    T1] scsi host0: Virtio SCSI HBA
[    0.134006] [    T1] tun: Universal TUN/TAP device driver, 1.6

=After this patch=
[    0.105891] [    T1] scsi host0: Virtio SCSI HBA
[    0.107868] [    T1] tun: Universal TUN/TAP device driver, 1.6

It reduces about 17ms on arm64 for virtio-scsi.

This patch changes the default kernel parameter:
1. If user specifies the scan mode, use that
2. If user doesn't specify it, and the block device is virtio-scsi, use
   "none" by default

[1] https://lwn.net/Articles/201898/
[2] https://github.com/kata-containers/agent/blob/649d44117a/device.go#L322

Fixes: #2560
Signed-off-by: Jia He <justin.he@arm.com
---
 pkg/katautils/config.go      | 18 ++++++++++++++----
 pkg/katautils/create_test.go |  4 ++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/pkg/katautils/config.go b/pkg/katautils/config.go
index b7b3ccd40d..14794a24ff 100644
--- a/pkg/katautils/config.go
+++ b/pkg/katautils/config.go
@@ -977,7 +977,6 @@ func SetKernelParams(runtimeConfig *oci.RuntimeConfig) error {
 	if runtimeConfig.HypervisorConfig.Debug {
 		strParams := vc.SerializeParams(defaultKernelParams, "=")
 		formatted := strings.Join(strParams, " ")
-
 		kataUtilsLogger.WithField("default-kernel-parameters", formatted).Debug()
 	}
 
@@ -989,7 +988,18 @@ func SetKernelParams(runtimeConfig *oci.RuntimeConfig) error {
 
 	// first, add default values
 	for _, p := range defaultKernelParams {
-		if err := (runtimeConfig).AddKernelParam(p); err != nil {
+		if err := runtimeConfig.AddKernelParam(p); err != nil {
+			return err
+		}
+	}
+
+	// set the scsi scan mode to none for virtio-scsi
+	if runtimeConfig.HypervisorConfig.BlockDeviceDriver == config.VirtioSCSI {
+		p := vc.Param{
+			Key:   "scsi_mod.scan",
+			Value: "none",
+		}
+		if err := runtimeConfig.AddKernelParam(p); err != nil {
 			return err
 		}
 	}
@@ -1004,7 +1014,7 @@ func SetKernelParams(runtimeConfig *oci.RuntimeConfig) error {
 		params := vc.KataAgentKernelParams(agentConfig)
 
 		for _, p := range params {
-			if err := (runtimeConfig).AddKernelParam(p); err != nil {
+			if err := runtimeConfig.AddKernelParam(p); err != nil {
 				return err
 			}
 		}
@@ -1012,7 +1022,7 @@ func SetKernelParams(runtimeConfig *oci.RuntimeConfig) error {
 
 	// now re-add the user-specified values so that they take priority.
 	for _, p := range userKernelParams {
-		if err := (runtimeConfig).AddKernelParam(p); err != nil {
+		if err := runtimeConfig.AddKernelParam(p); err != nil {
 			return err
 		}
 	}
diff --git a/pkg/katautils/create_test.go b/pkg/katautils/create_test.go
index 3e5eb370dc..e750cc2d48 100644
--- a/pkg/katautils/create_test.go
+++ b/pkg/katautils/create_test.go
@@ -208,6 +208,10 @@ func TestSetKernelParams(t *testing.T) {
 	err := SetKernelParams(&config)
 	assert.NoError(err)
 
+	config.HypervisorConfig.BlockDeviceDriver = "virtio-scsi"
+	err = SetKernelParams(&config)
+	assert.NoError(err)
+
 	if needSystemd(config.HypervisorConfig) {
 		assert.NotEmpty(config.HypervisorConfig.KernelParams)
 	}