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e1000: add interrupt mitigation support
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This patch partially implements the e1000 interrupt mitigation mechanisms.
Using a single QEMUTimer, it emulates the ITR register (which is the newer
mitigation register, recommended by Intel) and approximately emulates
RADV and TADV registers. TIDV and RDTR register functionalities are not
emulated (RDTR is only used to validate RADV, according to the e1000 specs).

RADV, TADV, TIDV and RDTR registers make up the older e1000 mitigation
mechanism and would need a timer each to be completely emulated. However,
a single timer has been used in order to reach a good compromise between
emulation accuracy and simplicity/efficiency.

The implemented mechanism can be enabled/disabled specifying the command
line e1000-specific boolean parameter "mitigation", e.g.

    qemu-system-x86_64 -device e1000,mitigation=on,... ...

For more information, see the Software developer's manual at
http://download.intel.com/design/network/manuals/8254x_GBe_SDM.pdf.

Interrupt mitigation boosts performance when the guest suffers from
an high interrupt rate (i.e. receiving short UDP packets at high packet
rate). For some numerical results see the following link
http://info.iet.unipi.it/~luigi/papers/20130520-rizzo-vm.pdf

Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Reviewed-by: Andreas Färber <afaerber@suse.de> (for pc-* machines)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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@vmaffione @stefanhaRH
vmaffione authored and stefanhaRH committed Sep 6, 2013
1 parent 067404b commit e9845f0
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Showing 4 changed files with 164 additions and 6 deletions.
16 changes: 14 additions & 2 deletions hw/i386/pc_piix.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -339,14 +339,25 @@ static void pc_xen_hvm_init(QEMUMachineInitArgs *args)
.desc = "Standard PC (i440FX + PIIX, 1996)", \
.hot_add_cpu = pc_hot_add_cpu

#define PC_I440FX_1_7_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
static QEMUMachine pc_i440fx_machine_v1_7 = {
PC_I440FX_1_7_MACHINE_OPTIONS,
.name = "pc-i440fx-1.7",
.alias = "pc",
.init = pc_init_pci,
.is_default = 1,
};

#define PC_I440FX_1_6_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS

static QEMUMachine pc_i440fx_machine_v1_6 = {
PC_I440FX_1_6_MACHINE_OPTIONS,
.name = "pc-i440fx-1.6",
.alias = "pc",
.init = pc_init_pci_1_6,
.is_default = 1,
.compat_props = (GlobalProperty[]) {
PC_COMPAT_1_6,
{ /* end of list */ }
},
};

static QEMUMachine pc_i440fx_machine_v1_5 = {
Expand Down Expand Up @@ -735,6 +746,7 @@ static QEMUMachine xenfv_machine = {

static void pc_machine_init(void)
{
qemu_register_machine(&pc_i440fx_machine_v1_7);
qemu_register_machine(&pc_i440fx_machine_v1_6);
qemu_register_machine(&pc_i440fx_machine_v1_5);
qemu_register_machine(&pc_i440fx_machine_v1_4);
Expand Down
15 changes: 14 additions & 1 deletion hw/i386/pc_q35.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -258,13 +258,25 @@ static void pc_q35_init_1_4(QEMUMachineInitArgs *args)
.desc = "Standard PC (Q35 + ICH9, 2009)", \
.hot_add_cpu = pc_hot_add_cpu

#define PC_Q35_1_7_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS

static QEMUMachine pc_q35_machine_v1_7 = {
PC_Q35_1_7_MACHINE_OPTIONS,
.name = "pc-q35-1.7",
.alias = "q35",
.init = pc_q35_init,
};

#define PC_Q35_1_6_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS

static QEMUMachine pc_q35_machine_v1_6 = {
PC_Q35_1_6_MACHINE_OPTIONS,
.name = "pc-q35-1.6",
.alias = "q35",
.init = pc_q35_init_1_6,
.compat_props = (GlobalProperty[]) {
PC_COMPAT_1_6,
{ /* end of list */ }
},
};

static QEMUMachine pc_q35_machine_v1_5 = {
Expand Down Expand Up @@ -293,6 +305,7 @@ static QEMUMachine pc_q35_machine_v1_4 = {

static void pc_q35_machine_init(void)
{
qemu_register_machine(&pc_q35_machine_v1_7);
qemu_register_machine(&pc_q35_machine_v1_6);
qemu_register_machine(&pc_q35_machine_v1_5);
qemu_register_machine(&pc_q35_machine_v1_4);
Expand Down
131 changes: 128 additions & 3 deletions hw/net/e1000.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -135,9 +135,16 @@ typedef struct E1000State_st {

QEMUTimer *autoneg_timer;

QEMUTimer *mit_timer; /* Mitigation timer. */
bool mit_timer_on; /* Mitigation timer is running. */
bool mit_irq_level; /* Tracks interrupt pin level. */
uint32_t mit_ide; /* Tracks E1000_TXD_CMD_IDE bit. */

/* Compatibility flags for migration to/from qemu 1.3.0 and older */
#define E1000_FLAG_AUTONEG_BIT 0
#define E1000_FLAG_MIT_BIT 1
#define E1000_FLAG_AUTONEG (1 << E1000_FLAG_AUTONEG_BIT)
#define E1000_FLAG_MIT (1 << E1000_FLAG_MIT_BIT)
uint32_t compat_flags;
} E1000State;

Expand All @@ -158,7 +165,8 @@ enum {
defreg(TORH), defreg(TORL), defreg(TOTH), defreg(TOTL),
defreg(TPR), defreg(TPT), defreg(TXDCTL), defreg(WUFC),
defreg(RA), defreg(MTA), defreg(CRCERRS),defreg(VFTA),
defreg(VET),
defreg(VET), defreg(RDTR), defreg(RADV), defreg(TADV),
defreg(ITR),
};

static void
Expand Down Expand Up @@ -245,10 +253,21 @@ static const uint32_t mac_reg_init[] = {
E1000_MANC_RMCP_EN,
};

/* Helper function, *curr == 0 means the value is not set */
static inline void
mit_update_delay(uint32_t *curr, uint32_t value)
{
if (value && (*curr == 0 || value < *curr)) {
*curr = value;
}
}

static void
set_interrupt_cause(E1000State *s, int index, uint32_t val)
{
PCIDevice *d = PCI_DEVICE(s);
uint32_t pending_ints;
uint32_t mit_delay;

if (val && (E1000_DEVID >= E1000_DEV_ID_82547EI_MOBILE)) {
/* Only for 8257x */
Expand All @@ -266,7 +285,57 @@ set_interrupt_cause(E1000State *s, int index, uint32_t val)
*/
s->mac_reg[ICS] = val;

qemu_set_irq(d->irq[0], (s->mac_reg[IMS] & s->mac_reg[ICR]) != 0);
pending_ints = (s->mac_reg[IMS] & s->mac_reg[ICR]);
if (!s->mit_irq_level && pending_ints) {
/*
* Here we detect a potential raising edge. We postpone raising the
* interrupt line if we are inside the mitigation delay window
* (s->mit_timer_on == 1).
* We provide a partial implementation of interrupt mitigation,
* emulating only RADV, TADV and ITR (lower 16 bits, 1024ns units for
* RADV and TADV, 256ns units for ITR). RDTR is only used to enable
* RADV; relative timers based on TIDV and RDTR are not implemented.
*/
if (s->mit_timer_on) {
return;
}
if (s->compat_flags & E1000_FLAG_MIT) {
/* Compute the next mitigation delay according to pending
* interrupts and the current values of RADV (provided
* RDTR!=0), TADV and ITR.
* Then rearm the timer.
*/
mit_delay = 0;
if (s->mit_ide &&
(pending_ints & (E1000_ICR_TXQE | E1000_ICR_TXDW))) {
mit_update_delay(&mit_delay, s->mac_reg[TADV] * 4);
}
if (s->mac_reg[RDTR] && (pending_ints & E1000_ICS_RXT0)) {
mit_update_delay(&mit_delay, s->mac_reg[RADV] * 4);
}
mit_update_delay(&mit_delay, s->mac_reg[ITR]);

if (mit_delay) {
s->mit_timer_on = 1;
timer_mod(s->mit_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
mit_delay * 256);
}
s->mit_ide = 0;
}
}

s->mit_irq_level = (pending_ints != 0);
qemu_set_irq(d->irq[0], s->mit_irq_level);
}

static void
e1000_mit_timer(void *opaque)
{
E1000State *s = opaque;

s->mit_timer_on = 0;
/* Call set_interrupt_cause to update the irq level (if necessary). */
set_interrupt_cause(s, 0, s->mac_reg[ICR]);
}

static void
Expand Down Expand Up @@ -307,6 +376,10 @@ static void e1000_reset(void *opaque)
int i;

timer_del(d->autoneg_timer);
timer_del(d->mit_timer);
d->mit_timer_on = 0;
d->mit_irq_level = 0;
d->mit_ide = 0;
memset(d->phy_reg, 0, sizeof d->phy_reg);
memmove(d->phy_reg, phy_reg_init, sizeof phy_reg_init);
memset(d->mac_reg, 0, sizeof d->mac_reg);
Expand Down Expand Up @@ -572,6 +645,7 @@ process_tx_desc(E1000State *s, struct e1000_tx_desc *dp)
struct e1000_context_desc *xp = (struct e1000_context_desc *)dp;
struct e1000_tx *tp = &s->tx;

s->mit_ide |= (txd_lower & E1000_TXD_CMD_IDE);
if (dtype == E1000_TXD_CMD_DEXT) { // context descriptor
op = le32_to_cpu(xp->cmd_and_length);
tp->ipcss = xp->lower_setup.ip_fields.ipcss;
Expand Down Expand Up @@ -1047,7 +1121,8 @@ static uint32_t (*macreg_readops[])(E1000State *, int) = {
getreg(TORL), getreg(TOTL), getreg(IMS), getreg(TCTL),
getreg(RDH), getreg(RDT), getreg(VET), getreg(ICS),
getreg(TDBAL), getreg(TDBAH), getreg(RDBAH), getreg(RDBAL),
getreg(TDLEN), getreg(RDLEN),
getreg(TDLEN), getreg(RDLEN), getreg(RDTR), getreg(RADV),
getreg(TADV), getreg(ITR),

[TOTH] = mac_read_clr8, [TORH] = mac_read_clr8, [GPRC] = mac_read_clr4,
[GPTC] = mac_read_clr4, [TPR] = mac_read_clr4, [TPT] = mac_read_clr4,
Expand All @@ -1069,6 +1144,8 @@ static void (*macreg_writeops[])(E1000State *, int, uint32_t) = {
[TDH] = set_16bit, [RDH] = set_16bit, [RDT] = set_rdt,
[IMC] = set_imc, [IMS] = set_ims, [ICR] = set_icr,
[EECD] = set_eecd, [RCTL] = set_rx_control, [CTRL] = set_ctrl,
[RDTR] = set_16bit, [RADV] = set_16bit, [TADV] = set_16bit,
[ITR] = set_16bit,
[RA ... RA+31] = &mac_writereg,
[MTA ... MTA+127] = &mac_writereg,
[VFTA ... VFTA+127] = &mac_writereg,
Expand Down Expand Up @@ -1150,6 +1227,11 @@ static void e1000_pre_save(void *opaque)
E1000State *s = opaque;
NetClientState *nc = qemu_get_queue(s->nic);

/* If the mitigation timer is active, emulate a timeout now. */
if (s->mit_timer_on) {
e1000_mit_timer(s);
}

if (!(s->compat_flags & E1000_FLAG_AUTONEG)) {
return;
}
Expand All @@ -1171,6 +1253,14 @@ static int e1000_post_load(void *opaque, int version_id)
E1000State *s = opaque;
NetClientState *nc = qemu_get_queue(s->nic);

if (!(s->compat_flags & E1000_FLAG_MIT)) {
s->mac_reg[ITR] = s->mac_reg[RDTR] = s->mac_reg[RADV] =
s->mac_reg[TADV] = 0;
s->mit_irq_level = false;
}
s->mit_ide = 0;
s->mit_timer_on = false;

/* nc.link_down can't be migrated, so infer link_down according
* to link status bit in mac_reg[STATUS].
* Alternatively, restart link negotiation if it was in progress. */
Expand All @@ -1190,6 +1280,28 @@ static int e1000_post_load(void *opaque, int version_id)
return 0;
}

static bool e1000_mit_state_needed(void *opaque)
{
E1000State *s = opaque;

return s->compat_flags & E1000_FLAG_MIT;
}

static const VMStateDescription vmstate_e1000_mit_state = {
.name = "e1000/mit_state",
.version_id = 1,
.minimum_version_id = 1,
.minimum_version_id_old = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT32(mac_reg[RDTR], E1000State),
VMSTATE_UINT32(mac_reg[RADV], E1000State),
VMSTATE_UINT32(mac_reg[TADV], E1000State),
VMSTATE_UINT32(mac_reg[ITR], E1000State),
VMSTATE_BOOL(mit_irq_level, E1000State),
VMSTATE_END_OF_LIST()
}
};

static const VMStateDescription vmstate_e1000 = {
.name = "e1000",
.version_id = 2,
Expand Down Expand Up @@ -1267,6 +1379,14 @@ static const VMStateDescription vmstate_e1000 = {
VMSTATE_UINT32_SUB_ARRAY(mac_reg, E1000State, MTA, 128),
VMSTATE_UINT32_SUB_ARRAY(mac_reg, E1000State, VFTA, 128),
VMSTATE_END_OF_LIST()
},
.subsections = (VMStateSubsection[]) {
{
.vmsd = &vmstate_e1000_mit_state,
.needed = e1000_mit_state_needed,
}, {
/* empty */
}
}
};

Expand Down Expand Up @@ -1316,6 +1436,8 @@ pci_e1000_uninit(PCIDevice *dev)

timer_del(d->autoneg_timer);
timer_free(d->autoneg_timer);
timer_del(d->mit_timer);
timer_free(d->mit_timer);
memory_region_destroy(&d->mmio);
memory_region_destroy(&d->io);
qemu_del_nic(d->nic);
Expand Down Expand Up @@ -1371,6 +1493,7 @@ static int pci_e1000_init(PCIDevice *pci_dev)
add_boot_device_path(d->conf.bootindex, dev, "/ethernet-phy@0");

d->autoneg_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, e1000_autoneg_timer, d);
d->mit_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, e1000_mit_timer, d);

return 0;
}
Expand All @@ -1385,6 +1508,8 @@ static Property e1000_properties[] = {
DEFINE_NIC_PROPERTIES(E1000State, conf),
DEFINE_PROP_BIT("autonegotiation", E1000State,
compat_flags, E1000_FLAG_AUTONEG_BIT, true),
DEFINE_PROP_BIT("mitigation", E1000State,
compat_flags, E1000_FLAG_MIT_BIT, true),
DEFINE_PROP_END_OF_LIST(),
};

Expand Down
8 changes: 8 additions & 0 deletions include/hw/i386/pc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -225,7 +225,15 @@ void pvpanic_init(ISABus *bus);

int e820_add_entry(uint64_t, uint64_t, uint32_t);

#define PC_COMPAT_1_6 \
{\
.driver = "e1000",\
.property = "mitigation",\
.value = "off",\
}

#define PC_COMPAT_1_5 \
PC_COMPAT_1_6, \
{\
.driver = "Conroe-" TYPE_X86_CPU,\
.property = "model",\
Expand Down

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