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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2024 Intel Corporation
*
* Verify KVM correctly emulates the APIC bus frequency when the VMM configures
* the frequency via KVM_CAP_X86_APIC_BUS_CYCLES_NS. Start the APIC timer by
* programming TMICT (timer initial count) to the largest value possible (so
* that the timer will not expire during the test). Then, after an arbitrary
* amount of time has elapsed, verify TMCCT (timer current count) is within 1%
* of the expected value based on the time elapsed, the APIC bus frequency, and
* the programmed TDCR (timer divide configuration register).
*/
#include "apic.h"
#include "test_util.h"
/*
* Possible TDCR values with matching divide count. Used to modify APIC
* timer frequency.
*/
static const struct {
const uint32_t tdcr;
const uint32_t divide_count;
} tdcrs[] = {
{0x0, 2},
{0x1, 4},
{0x2, 8},
{0x3, 16},
{0x8, 32},
{0x9, 64},
{0xa, 128},
{0xb, 1},
};
static bool is_x2apic;
static void apic_enable(void)
{
if (is_x2apic)
x2apic_enable();
else
xapic_enable();
}
static uint32_t apic_read_reg(unsigned int reg)
{
return is_x2apic ? x2apic_read_reg(reg) : xapic_read_reg(reg);
}
static void apic_write_reg(unsigned int reg, uint32_t val)
{
if (is_x2apic)
x2apic_write_reg(reg, val);
else
xapic_write_reg(reg, val);
}
static void apic_guest_code(uint64_t apic_hz, uint64_t delay_ms)
{
uint64_t tsc_hz = guest_tsc_khz * 1000;
const uint32_t tmict = ~0u;
uint64_t tsc0, tsc1, freq;
uint32_t tmcct;
int i;
apic_enable();
/*
* Setup one-shot timer. The vector does not matter because the
* interrupt should not fire.
*/
apic_write_reg(APIC_LVTT, APIC_LVT_TIMER_ONESHOT | APIC_LVT_MASKED);
for (i = 0; i < ARRAY_SIZE(tdcrs); i++) {
apic_write_reg(APIC_TDCR, tdcrs[i].tdcr);
apic_write_reg(APIC_TMICT, tmict);
tsc0 = rdtsc();
udelay(delay_ms * 1000);
tmcct = apic_read_reg(APIC_TMCCT);
tsc1 = rdtsc();
/*
* Stop the timer _after_ reading the current, final count, as
* writing the initial counter also modifies the current count.
*/
apic_write_reg(APIC_TMICT, 0);
freq = (tmict - tmcct) * tdcrs[i].divide_count * tsc_hz / (tsc1 - tsc0);
/* Check if measured frequency is within 5% of configured frequency. */
__GUEST_ASSERT(freq < apic_hz * 105 / 100 && freq > apic_hz * 95 / 100,
"Frequency = %lu (wanted %lu - %lu), bus = %lu, div = %u, tsc = %lu",
freq, apic_hz * 95 / 100, apic_hz * 105 / 100,
apic_hz, tdcrs[i].divide_count, tsc_hz);
}
GUEST_DONE();
}
static void test_apic_bus_clock(struct kvm_vcpu *vcpu)
{
bool done = false;
struct ucall uc;
while (!done) {
vcpu_run(vcpu);
TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
switch (get_ucall(vcpu, &uc)) {
case UCALL_DONE:
done = true;
break;
case UCALL_ABORT:
REPORT_GUEST_ASSERT(uc);
break;
default:
TEST_FAIL("Unknown ucall %lu", uc.cmd);
break;
}
}
}
static void run_apic_bus_clock_test(uint64_t apic_hz, uint64_t delay_ms,
bool x2apic)
{
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
int ret;
is_x2apic = x2apic;
vm = vm_create(1);
sync_global_to_guest(vm, is_x2apic);
vm_enable_cap(vm, KVM_CAP_X86_APIC_BUS_CYCLES_NS,
NSEC_PER_SEC / apic_hz);
vcpu = vm_vcpu_add(vm, 0, apic_guest_code);
vcpu_args_set(vcpu, 2, apic_hz, delay_ms);
ret = __vm_enable_cap(vm, KVM_CAP_X86_APIC_BUS_CYCLES_NS,
NSEC_PER_SEC / apic_hz);
TEST_ASSERT(ret < 0 && errno == EINVAL,
"Setting of APIC bus frequency after vCPU is created should fail.");
if (!is_x2apic)
virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
test_apic_bus_clock(vcpu);
kvm_vm_free(vm);
}
static void help(char *name)
{
puts("");
printf("usage: %s [-h] [-d delay] [-f APIC bus freq]\n", name);
puts("");
printf("-d: Delay (in msec) guest uses to measure APIC bus frequency.\n");
printf("-f: The APIC bus frequency (in MHz) to be configured for the guest.\n");
puts("");
}
int main(int argc, char *argv[])
{
/*
* Arbitrarilty default to 25MHz for the APIC bus frequency, which is
* different enough from the default 1GHz to be interesting.
*/
uint64_t apic_hz = 25 * 1000 * 1000;
uint64_t delay_ms = 100;
int opt;
TEST_REQUIRE(kvm_has_cap(KVM_CAP_X86_APIC_BUS_CYCLES_NS));
while ((opt = getopt(argc, argv, "d:f:h")) != -1) {
switch (opt) {
case 'f':
apic_hz = atoi_positive("APIC bus frequency", optarg) * 1000 * 1000;
break;
case 'd':
delay_ms = atoi_positive("Delay in milliseconds", optarg);
break;
case 'h':
default:
help(argv[0]);
exit(KSFT_SKIP);
}
}
run_apic_bus_clock_test(apic_hz, delay_ms, false);
run_apic_bus_clock_test(apic_hz, delay_ms, true);
}
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