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virtcontainers: clh: Set the serial to NULL instead of OFF
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The guest Linux kernel might try to access the serial port, and in case
the serial is "off", this might cause some slowness because the port is
not emulated at all. Problem is, when the port is not emulated, the
default value when reading the I/O port will be 0, which has a special
meaning in case of the serial port. It means there is some data ready
to be read, which the kernel might try to read for some time, causing
global system slowness.

That's why it's safer to use "null" by default as this means the serial
port will be emulated but anything written to it will be redirected to
/dev/null.

Fixes #2437

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
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Sebastien Boeuf committed Feb 4, 2020
1 parent a91cb13 commit b2fb86f
Showing 1 changed file with 2 additions and 1 deletion.
3 changes: 2 additions & 1 deletion virtcontainers/clh.go
Original file line number Diff line number Diff line change
Expand Up @@ -265,7 +265,7 @@ func (clh *cloudHypervisor) createSandbox(ctx context.Context, id string, networ

} else {
clh.vmconfig.Serial = chclient.ConsoleConfig{
Mode: cctOFF,
Mode: cctNULL,
}
}

Expand Down Expand Up @@ -761,6 +761,7 @@ func MaxClhVCPUs() uint32 {
const (
cctOFF string = "Off"
cctFILE string = "File"
cctNULL string = "Null"
)

const (
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