interrupt remap 和 posted interupt 是什么关系?
关于投递 msi 中断的硬件行为，可以参考如下 qemu 的调用路线:
- main
- qemu_default_main
- qemu_main_loop
- main_loop_wait
- os_host_main_loop_wait
- glib_pollfds_poll
- g_main_context_dispatch
- g_main_context_dispatch_unlocked
- aio_ctx_dispatch
- aio_dispatch
- aio_bh_poll
- blk_aio_complete_bh
- blk_aio_complete
- blk_aio_complete
- virtio_blk_rw_complete
- address_space_stl_le
- address_space_stl_internal
- memory_region_dispatch_write
- access_with_adjusted_size
- memory_region_write_accessor
- kvm_apic_mem_write (写入到 LAPIC mmio 空间)
- kvm_send_msi
- kvm_irqchip_send_msi
- kvm_send_msi
- kvm_apic_mem_write (写入到 LAPIC mmio 空间)
- memory_region_write_accessor
- access_with_adjusted_size
- memory_region_dispatch_write
- address_space_stl_internal
- address_space_stl_le
- virtio_blk_rw_complete
- blk_aio_complete
- blk_aio_complete
- blk_aio_complete_bh
- aio_bh_poll
- aio_dispatch
- aio_ctx_dispatch
- g_main_context_dispatch_unlocked
- g_main_context_dispatch
- glib_pollfds_poll
- os_host_main_loop_wait
- main_loop_wait
- qemu_main_loop
- qemu_default_main
设备产生的是 MSI/MSI-X 中断，本质是一次 DMA 写 LAPIC MMIO 空间的操作。
如果不加控制，设备可以：
- 向任意 CPU
- 任意 vector
- 任意 destination ID
- 写中断
所以，虽然硬件直通到虚拟机中，msix-table 不能被 vCPU 直接写，虚拟机操作直通设备的 MSI 必须被拦截， 然后根据 itre 来进行投递
在直通模式，下IRTE 决定一切
- IRTE 中包含：
- 是否允许该中断
- 目标 vCPU / pCPU
- vector
- delivery mode
- 是否是 virtual / posted interrupt
- 设备无法越权修改任何字段。
关键代码
- drivers/iommu/intel/irq_remapping.c
struct irq_remap_ops intel_irq_remap_ops = {
.prepare = intel_prepare_irq_remapping,
.enable = intel_enable_irq_remapping,
.disable = disable_irq_remapping,
.reenable = reenable_irq_remapping,
.enable_faulting = enable_drhd_fault_handling,
};
static const struct irq_domain_ops intel_ir_domain_ops = {
.select = intel_irq_remapping_select,
.alloc = intel_irq_remapping_alloc,
.free = intel_irq_remapping_free,
.activate = intel_irq_remapping_activate,
.deactivate = intel_irq_remapping_deactivate,
};
static struct irq_chip intel_ir_chip = {
.name = "INTEL-IR",
.irq_ack = apic_ack_irq,
.irq_set_affinity = intel_ir_set_affinity,
.irq_compose_msi_msg = intel_ir_compose_msi_msg,
.irq_set_vcpu_affinity = intel_ir_set_vcpu_affinity,
};
irq_remap_ops 是设备初始化相关的， intel_ir_chip 和 intel_ir_domain_ops 就是我们熟悉的东西了 用于添加一个的映射。
include/linux/dmar.h
struct irte {
union {
struct {
union {
/* Shared between remapped and posted mode*/
struct {
__u64 present : 1, /* 0 */
fpd : 1, /* 1 */
__res0 : 6, /* 2 - 6 */
avail : 4, /* 8 - 11 */
__res1 : 3, /* 12 - 14 */
pst : 1, /* 15 */
vector : 8, /* 16 - 23 */
__res2 : 40; /* 24 - 63 */
};
/* Remapped mode */
struct {
__u64 r_present : 1, /* 0 */
r_fpd : 1, /* 1 */
dst_mode : 1, /* 2 */
redir_hint : 1, /* 3 */
trigger_mode : 1, /* 4 */
dlvry_mode : 3, /* 5 - 7 */
r_avail : 4, /* 8 - 11 */
r_res0 : 4, /* 12 - 15 */
r_vector : 8, /* 16 - 23 */
r_res1 : 8, /* 24 - 31 */
dest_id : 32; /* 32 - 63 */
};
/* Posted mode */
struct {
__u64 p_present : 1, /* 0 */
p_fpd : 1, /* 1 */
p_res0 : 6, /* 2 - 7 */
p_avail : 4, /* 8 - 11 */
p_res1 : 2, /* 12 - 13 */
p_urgent : 1, /* 14 */
p_pst : 1, /* 15 */
p_vector : 8, /* 16 - 23 */
p_res2 : 14, /* 24 - 37 */
pda_l : 26; /* 38 - 63 */
};
__u64 low;
};
union {
/* Shared between remapped and posted mode*/
struct {
__u64 sid : 16, /* 64 - 79 */
sq : 2, /* 80 - 81 */
svt : 2, /* 82 - 83 */
__res3 : 44; /* 84 - 127 */
};
/* Posted mode*/
struct {
__u64 p_sid : 16, /* 64 - 79 */
p_sq : 2, /* 80 - 81 */
p_svt : 2, /* 82 - 83 */
p_res3 : 12, /* 84 - 95 */
pda_h : 32; /* 96 - 127 */
};
__u64 high;
};
};
#ifdef CONFIG_IRQ_REMAP
__u128 irte;
#endif
};
};
@[
intel_ir_set_vcpu_affinity+5
irq_set_vcpu_affinity+206
vmx_pi_update_irte+84
kvm_pi_update_irte+131
kvm_arch_irq_bypass_add_producer+143
__connect+88
irq_bypass_register_producer+181
vfio_msi_set_vector_signal+427
vfio_msi_set_block+89
vfio_pci_core_ioctl+684
vfio_device_fops_unl_ioctl+140
__x64_sys_ioctl+150
do_syscall_64+97
entry_SYSCALL_64_after_hwframe+118
]: 66
@[
intel_ir_compose_msi_msg+5
irq_chip_compose_msi_msg+47
msi_domain_activate+70
__irq_domain_activate_irq+80
irq_domain_activate_irq+45
__msi_domain_alloc_irqs+700
msi_domain_alloc_irqs_all_locked+91
__pci_enable_msix_range+980
pci_alloc_irq_vectors_affinity+173
vfio_pci_set_msi_trigger+157
vfio_pci_core_ioctl+2536
vfio_device_fops_unl_ioctl+129
__x64_sys_ioctl+148
do_syscall_64+59
entry_SYSCALL_64_after_hwframe+110
]: 7
如果是 amd ，那么类似的结果:
b'modify_irte_ga'
b'irq_remapping_activate'
b'__irq_domain_activate_irq'
b'__irq_domain_activate_irq'
b'irq_domain_activate_irq'
b'__setup_irq'
b'request_threaded_irq'
b'vfio_msi_set_vector_signal'
b'vfio_msi_set_block'
b'vfio_pci_set_msi_trigger'
b'vfio_pci_ioctl'
b'do_vfs_ioctl'
b'ksys_ioctl'
b'__x64_sys_ioctl'
b'do_syscall_64'
b'entry_SYSCALL_64_after_hwframe'
b'[unknown]'
intremap 几个参数的作用
intremap= [X86-64, Intel-IOMMU]
on enable Interrupt Remapping (default)
off disable Interrupt Remapping
nosid disable Source ID checking
no_x2apic_optout
BIOS x2APIC opt-out request will be ignored
nopost disable Interrupt Posting
static __init int setup_irqremap(char *str)
{
if (!str)
return -EINVAL;
while (*str) {
if (!strncmp(str, "on", 2)) {
disable_irq_remap = 0;
disable_irq_post = 0;
} else if (!strncmp(str, "off", 3)) {
disable_irq_remap = 1;
disable_irq_post = 1;
} else if (!strncmp(str, "nosid", 5))
disable_sourceid_checking = 1;
else if (!strncmp(str, "no_x2apic_optout", 16))
no_x2apic_optout = 1;
else if (!strncmp(str, "nopost", 6))
disable_irq_post = 1;
else if (IS_ENABLED(CONFIG_X86_POSTED_MSI) && !strncmp(str, "posted_msi", 10))
enable_posted_msi = true;
str += strcspn(str, ",");
while (*str == ',')
str++;
}
return 0;
}
early_param("intremap", setup_irqremap);
可以看到代码里面实际上多了一个 posted_msi ，这个东西我们在 docs/kernel/vfio/int-posted-msi.md 还不清楚的东西也就是
- nosid
- no_x2apic_optout
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