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[arch][x86] move the KVM clock stuff to arch from platform

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One can argue it more logically fits there, and eventually more KVM
features will arrive in this file that have nothing to do with timers.
This commit is contained in:
Travis Geiselbrecht
2025-04-06 19:28:08 -07:00
parent 71e795de19
commit 3013662345
2 changed files with 123 additions and 104 deletions
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122
arch/x86/pv.c
View File

@@ -5,3 +5,125 @@
* license that can be found in the LICENSE file or at
* https://opensource.org/licenses/MIT
*/
#include "arch/x86/pv.h"
#include <lk/err.h>
#include <lk/trace.h>
#include <assert.h>
#include <stdint.h>
#include <inttypes.h>
#include <arch/x86/feature.h>
#include <kernel/vm.h>
#define LOCAL_TRACE 0
#if !X86_LEGACY
// Deals with paravirtualized clock sources and event timers on the PC platform,
// specifically KVM.
// From https://www.kernel.org/doc/html/v6.14/virt/kvm/x86/msr.html
struct pvclock_wall_clock {
uint32_t version;
uint32_t sec;
uint32_t nsec;
} __PACKED;
static_assert(sizeof(struct pvclock_wall_clock) == 12, "pvclock_wall_clock size mismatch");
struct pvclock_vcpu_time_info {
uint32_t version;
uint32_t pad0;
uint64_t tsc_timestamp;
uint64_t system_time;
uint32_t tsc_to_system_mul;
int8_t tsc_shift;
uint8_t flags;
uint8_t pad[2];
} __PACKED;
static_assert(sizeof(struct pvclock_vcpu_time_info) == 32, "pvclock_vcpu_time_info size mismatch");
#define VCPU_TIME_INFO_FLAG_STABLE 0x1
static volatile struct pvclock_wall_clock *wall_clock;
static volatile struct pvclock_vcpu_time_info *vcpu_time_info;
status_t pvclock_init(void) {
uint32_t clocksource_msr_base = 0;
if (x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE)) {
clocksource_msr_base = 0x11;
}
if (x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE2)) {
clocksource_msr_base = 0x4b564d00;
}
if (!clocksource_msr_base) {
return ERR_NOT_SUPPORTED;
}
dprintf(INFO, "pv_clock: clocksource detected, msr base %#x\n", clocksource_msr_base);
// map a page of memory and point the KVM clocksource msrs at it
void *clocksource_page;
status_t err = vmm_alloc(vmm_get_kernel_aspace(), "lapic", PAGE_SIZE, &clocksource_page, 0, 0, 0);
if (err != NO_ERROR) {
printf("pv_clock: failed to allocate page for clocksource msrs\n");
return err;
}
paddr_t paddr;
arch_mmu_query(&vmm_get_kernel_aspace()->arch_aspace, (vaddr_t)clocksource_page, &paddr, NULL);
LTRACEF("clocksource page %p, paddr %#" PRIxPTR "\n", clocksource_page, paddr);
write_msr(clocksource_msr_base, paddr);
write_msr(clocksource_msr_base + 1, paddr + sizeof(struct pvclock_wall_clock) + 1);
wall_clock = (struct pvclock_wall_clock *)clocksource_page;
vcpu_time_info = (struct pvclock_vcpu_time_info *)(wall_clock + 1);
dprintf(SPEW, "pv_clock: wall clock version %u, sec %u, nsec %u\n",
wall_clock->version, wall_clock->sec, wall_clock->nsec);
dprintf(SPEW, "pv_clock: vcpu time info version %u, tsc timestamp %llu, system time %llu\n",
vcpu_time_info->version, vcpu_time_info->tsc_timestamp, vcpu_time_info->system_time);
dprintf(SPEW, "pv_clock: tsc to system mul %u, tsc shift %d, flags %u\n",
vcpu_time_info->tsc_to_system_mul, vcpu_time_info->tsc_shift, vcpu_time_info->flags);
return NO_ERROR;
}
uint64_t pvclock_get_tsc_freq(void) {
if (!vcpu_time_info) {
return 0;
}
uint32_t tsc_mul = 0;
int8_t tsc_shift = 0;
uint32_t pre_version = 0, post_version = 0;
do {
pre_version = vcpu_time_info->version;
if (pre_version % 2 != 0) {
asm("pause");
continue;
}
tsc_mul = vcpu_time_info->tsc_to_system_mul;
tsc_shift = vcpu_time_info->tsc_shift;
post_version = vcpu_time_info->version;
} while (pre_version != post_version);
uint64_t tsc_khz = 1000000ULL << 32;
tsc_khz = tsc_khz / tsc_mul;
if (tsc_shift > 0) {
tsc_khz >>= tsc_shift;
} else {
tsc_khz <<= -tsc_shift;
}
return tsc_khz * 1000;
}
bool pv_clock_is_stable(void) {
if (!vcpu_time_info) {
return false;
}
bool is_stable = (vcpu_time_info->flags & VCPU_TIME_INFO_FLAG_STABLE) ||
x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE_STABLE);
return is_stable;
}
#endif // !X86_LEGACY

105
platform/pc/timer.c
View File

@@ -20,6 +20,7 @@
#include <arch/x86.h>
#include <arch/x86/feature.h>
#include <arch/x86/lapic.h>
#include <arch/x86/pv.h>
#include <inttypes.h>
#include <lib/fixed_point.h>
@@ -78,115 +79,11 @@ lk_bigtime_t current_time_hires(void) {
}
}
// From https://www.kernel.org/doc/html/v6.14/virt/kvm/x86/msr.html
struct pvclock_wall_clock {
uint32_t version;
uint32_t sec;
uint32_t nsec;
} __PACKED;
static_assert(sizeof(struct pvclock_wall_clock) == 12, "pvclock_wall_clock size mismatch");
struct pvclock_vcpu_time_info {
uint32_t version;
uint32_t pad0;
uint64_t tsc_timestamp;
uint64_t system_time;
uint32_t tsc_to_system_mul;
int8_t tsc_shift;
uint8_t flags;
uint8_t pad[2];
} __PACKED;
static_assert(sizeof(struct pvclock_vcpu_time_info) == 32, "pvclock_vcpu_time_info size mismatch");
static volatile struct pvclock_wall_clock *wall_clock;
static volatile struct pvclock_vcpu_time_info *vcpu_time_info;
status_t pvclock_init(void) {
uint32_t clocksource_msr_base = 0;
if (x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE)) {
clocksource_msr_base = 0x11;
}
if (x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE2)) {
clocksource_msr_base = 0x4b564d00;
}
if (!clocksource_msr_base) {
return ERR_NOT_SUPPORTED;
}
dprintf(INFO, "pv_clock: clocksource detected, msr base %#x\n", clocksource_msr_base);
// map a page of memory and point the KVM clocksource msrs at it
void *clocksource_page;
status_t err = vmm_alloc(vmm_get_kernel_aspace(), "lapic", PAGE_SIZE, &clocksource_page, 0, 0, 0);
if (err != NO_ERROR) {
printf("pv_clock: failed to allocate page for clocksource msrs\n");
return err;
}
paddr_t paddr;
arch_mmu_query(&vmm_get_kernel_aspace()->arch_aspace, (vaddr_t)clocksource_page, &paddr, NULL);
LTRACEF("clocksource page %p, paddr %#" PRIxPTR "\n", clocksource_page, paddr);
write_msr(clocksource_msr_base, paddr);
write_msr(clocksource_msr_base + 1, paddr + sizeof(struct pvclock_wall_clock) + 1);
wall_clock = (struct pvclock_wall_clock *)clocksource_page;
vcpu_time_info = (struct pvclock_vcpu_time_info *)(wall_clock + 1);
dprintf(SPEW, "pv_clock: wall clock version %u, sec %u, nsec %u\n",
wall_clock->version, wall_clock->sec, wall_clock->nsec);
dprintf(SPEW, "pv_clock: vcpu time info version %u, tsc timestamp %llu, system time %llu\n",
vcpu_time_info->version, vcpu_time_info->tsc_timestamp, vcpu_time_info->system_time);
dprintf(SPEW, "pv_clock: tsc to system mul %u, tsc shift %d, flags %u\n",
vcpu_time_info->tsc_to_system_mul, vcpu_time_info->tsc_shift, vcpu_time_info->flags);
return NO_ERROR;
}
// Convert lk_time_t to TSC ticks
uint64_t time_to_tsc_ticks(lk_time_t time) {
return u64_mul_u32_fp32_64(time, timebase_to_tsc);
}
uint64_t pvclock_get_tsc_freq(void) {
uint32_t tsc_mul = 0;
int8_t tsc_shift = 0;
if (!vcpu_time_info) {
return 0;
}
uint32_t pre_version = 0, post_version = 0;
do {
pre_version = vcpu_time_info->version;
if (pre_version % 2 != 0) {
asm("pause");
continue;
}
tsc_mul = vcpu_time_info->tsc_to_system_mul;
tsc_shift = vcpu_time_info->tsc_shift;
post_version = vcpu_time_info->version;
} while (pre_version != post_version);
uint64_t tsc_khz = 1000000ULL << 32;
tsc_khz = tsc_khz / tsc_mul;
if (tsc_shift > 0) {
tsc_khz >>= tsc_shift;
} else {
tsc_khz <<= -tsc_shift;
}
return tsc_khz * 1000;
}
bool pv_clock_is_stable(void) {
if (!vcpu_time_info) {
return false;
}
bool is_stable = (vcpu_time_info->flags & (1<<0)) ||
x86_feature_test(X86_FEATURE_KVM_CLOCKSOURCE_STABLE);
return is_stable;
}
void pc_init_timer(unsigned int level) {
// Initialize the PIT, it's always present in PC hardware
pit_init();