From 2f4911566e9701c4f207864ebc564471812439e2 Mon Sep 17 00:00:00 2001
From: Ralf Haferkamp <rhafer@suse.com>
Date: Wed, 15 Jan 2020 12:01:28 +0100
Subject: [PATCH] agent: Fix mem-hotplug on x86 when ARCH_MEMORY_PROBE is set

Don't use the /sys/devices/system/memory/probe interface on architectures
where the firmware (ACPI) is notifying the system of hotplugged memory.
This fixes an issue with the agent erroring out when the guest-kernel is
compiled with CONFIG_ARCH_MEMORY_PROBE=y.

Fixes: #712
Signed-off-by: Ralf Haferkamp <rhafer@suse.com>
---
 grpc.go      | 19 ++++++++++++++++++-
 grpc_test.go | 26 ++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/grpc.go b/grpc.go
index ea0d7afa9..4c0dea39e 100644
--- a/grpc.go
+++ b/grpc.go
@@ -54,6 +54,7 @@ var (
 	sysfsMemOnlinePath          = "/sys/devices/system/memory"
 	sysfsMemoryBlockSizePath    = "/sys/devices/system/memory/block_size_bytes"
 	sysfsMemoryHotplugProbePath = "/sys/devices/system/memory/probe"
+	sysfsAcpiMemoryHotplugPath  = "/sys/firmware/acpi/hotplug/memory/enabled"
 	sysfsConnectedCPUsPath      = filepath.Join(sysfsCPUOnlinePath, "online")
 	containersRootfsPath        = "/run"
 
@@ -1576,6 +1577,16 @@ func (a *agentGRPC) ReseedRandomDev(ctx context.Context, req *pb.ReseedRandomDev
 	return emptyResp, reseedRNG(req.Data)
 }
 
+func (a *agentGRPC) haveAcpiMemoryHotplug() bool {
+	enabled, err := ioutil.ReadFile(sysfsAcpiMemoryHotplugPath)
+	if err != nil {
+		return false
+	} else if strings.TrimSpace(string(enabled)) == "1" {
+		return true
+	}
+	return false
+}
+
 func (a *agentGRPC) GetGuestDetails(ctx context.Context, req *pb.GuestDetailsRequest) (*pb.GuestDetailsResponse, error) {
 	var details pb.GuestDetailsResponse
 	if req.MemBlockSize {
@@ -1603,7 +1614,13 @@ func (a *agentGRPC) GetGuestDetails(ctx context.Context, req *pb.GuestDetailsReq
 		} else if err != nil {
 			return nil, err
 		} else {
-			details.SupportMemHotplugProbe = true
+			// Avoid triggering memory hotplugging notifications when ACPI
+			// hotplugging is enabled
+			if a.haveAcpiMemoryHotplug() {
+				details.SupportMemHotplugProbe = false
+			} else {
+				details.SupportMemHotplugProbe = true
+			}
 		}
 	}
 
diff --git a/grpc_test.go b/grpc_test.go
index 768cd1959..4bddb0535 100644
--- a/grpc_test.go
+++ b/grpc_test.go
@@ -843,12 +843,38 @@ func TestGetGuestDetails(t *testing.T) {
 	probeFile, err := ioutil.TempFile("", "probe")
 	assert.NoError(err)
 
+	// sysfsAcpiMemoryHotplugPath exist and is 1
+	hotplugEnabledFile, err := ioutil.TempFile("", "enabled")
+	assert.NoError(err)
+	_, err = hotplugEnabledFile.WriteString("1")
+	assert.NoError(err)
+	hotplugEnabledFile.Sync()
+
 	oldSysfsMemoryHotplugProbePath := sysfsMemoryHotplugProbePath
+	oldSysfsAcpiMemoryHotplugPath := sysfsAcpiMemoryHotplugPath
 	defer func() {
 		sysfsMemoryHotplugProbePath = oldSysfsMemoryHotplugProbePath
+		sysfsAcpiMemoryHotplugPath = oldSysfsAcpiMemoryHotplugPath
 	}()
 
 	sysfsMemoryHotplugProbePath = probeFile.Name()
+	sysfsAcpiMemoryHotplugPath = hotplugEnabledFile.Name()
+	resp, err = a.GetGuestDetails(context.TODO(), req)
+	assert.NoError(err)
+	assert.Equal(resp.SupportMemHotplugProbe, false)
+
+	// sysfsAcpiMemoryHotplugPath exist and is 0
+	_, err = hotplugEnabledFile.Seek(0, 0)
+	assert.NoError(err)
+	_, err = hotplugEnabledFile.WriteString("0")
+	assert.NoError(err)
+	hotplugEnabledFile.Sync()
+	resp, err = a.GetGuestDetails(context.TODO(), req)
+	assert.NoError(err)
+	assert.Equal(resp.SupportMemHotplugProbe, true)
+
+	// sysfsAcpiMemoryHotplugPath does not exist
+	os.Remove(sysfsAcpiMemoryHotplugPath)
 	resp, err = a.GetGuestDetails(context.TODO(), req)
 	assert.NoError(err)
 	assert.Equal(resp.SupportMemHotplugProbe, true)