Re: [PATCH 5/13] KVM: virtualization infrastructure

From: Arnd Bergmann
Date: Mon Oct 23 2006 - 15:35:36 EST

On Monday 23 October 2006 15:30, Avi Kivity wrote:
> - ioctl()
> - mmap()
> - vcpu context management (vcpu_load/vcpu_put)
> - some control register logic

Let me comment on coding style for now, I might come back with
contents when I understand more of the code.

> +static struct dentry *debugfs_dir;
> +static struct dentry *debugfs_pf_fixed;
> +static struct dentry *debugfs_pf_guest;
> +static struct dentry *debugfs_tlb_flush;
> +static struct dentry *debugfs_invlpg;
> +static struct dentry *debugfs_exits;
> +static struct dentry *debugfs_io_exits;
> +static struct dentry *debugfs_mmio_exits;
> +static struct dentry *debugfs_signal_exits;
> +static struct dentry *debugfs_irq_exits;

How about making these an array?

> +static int rmode_tss_base(struct kvm* kvm);
> +static void set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
> +static void __set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
> +static void lmsw(struct kvm_vcpu *vcpu, unsigned long msw);
> +static void set_cr3(struct kvm_vcpu *vcpu, unsigned long cr0);
> +static void set_cr4(struct kvm_vcpu *vcpu, unsigned long cr0);
> +static void __set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
> +#ifdef __x86_64__
> +static void __set_efer(struct kvm_vcpu *vcpu, u64 efer);
> +#endif

In general, you should try to avoid forward declarations for
static functions. The expected reading order is that static
functions are called only from other functions below them
in the same file, or through callbacks.

> +struct descriptor_table {
> + u16 limit;
> + unsigned long base;
> +} __attribute__((packed));

Is this a hardware structure? If not, packing it only
make accesses rather inefficient.

> +static void get_gdt(struct descriptor_table *table)
> +{
> + asm ( "sgdt %0" : "=m"(*table) );
> +}

Spacing:

asm ("sgdt %0" : "=m" (*table));

> +static void load_fs(u16 sel)
> +{
> + asm ( "mov %0, %%fs\n" : : "g"(sel) );
> +}
> +
> +static void load_gs(u16 sel)
> +{
> + asm ( "mov %0, %%gs\n" : : "g"(sel) );
> +}

Remove the '\n'.

> +struct segment_descriptor {
> + u16 limit_low;
> + u16 base_low;
> + u8 base_mid;
> + u8 type : 4;
> + u8 system : 1;
> + u8 dpl : 2;
> + u8 present : 1;
> + u8 limit_high : 4;
> + u8 avl : 1;
> + u8 long_mode : 1;
> + u8 default_op : 1;
> + u8 granularity : 1;
> + u8 base_high;
> +} __attribute__((packed));

Bitfields are generally frowned upon. It's better to define
constants for each of these and use a u64.

> +
> +#ifdef __x86_64__
> +// LDT or TSS descriptor in the GDT. 16 bytes.
> +struct segment_descriptor_64 {
> + struct segment_descriptor s;
> + u32 base_higher;
> + u32 pad_zero;
> +} __attribute__((packed));
> +#endif

No need for packing this.

> +
> +DEFINE_PER_CPU(struct vmcs *, vmxarea);
> +DEFINE_PER_CPU(struct vmcs *, current_vmcs);

If you make these

DEFINE_PER_CPU(struct vmcs, vmxarea);
DEFINE_PER_CPU(struct vmcs, current_vmcs);

you no longer need to handle allocation of the structures
yourself. Also, they should be 'static DEFINE_PER_CPU' if
possible.

> +static void set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
> +{
> + if (cr0 & CR0_RESEVED_BITS) {
> + printk("set_cr0: 0x%lx #GP, reserved bits (0x%lx)\n", cr0, guest_cr0());
> + inject_gp(vcpu);
> + return;
> + }
> +
> + if ((cr0 & CR0_NW_MASK) && !(cr0 & CR0_CD_MASK)) {
> + printk("set_cr0: #GP, CD == 0 && NW == 1\n");
> + inject_gp(vcpu);
> + return;
> + }
> +
> + if ((cr0 & CR0_PG_MASK) && !(cr0 & CR0_PE_MASK)) {
> + printk("set_cr0: #GP, set PG flag and a clear PE flag\n");
> + inject_gp(vcpu);
> + return;
> + }
> +
> + if (is_paging()) {
> +#ifdef __x86_64__
> + if (!(cr0 & CR0_PG_MASK)) {
> + vcpu->shadow_efer &= ~EFER_LMA;
> + vmcs_write32(VM_ENTRY_CONTROLS,
> + vmcs_read32(VM_ENTRY_CONTROLS) &
> + ~VM_ENTRY_CONTROLS_IA32E_MASK);
> + }
> +#endif
> + } else if ((cr0 & CR0_PG_MASK)) {
> +#ifdef __x86_64__
> + if ((vcpu->shadow_efer & EFER_LME)) {
> + u32 guest_cs_ar;
> + u32 guest_tr_ar;
> + if (!is_pae()) {
> + printk("set_cr0: #GP, start paging in "
> + "long mode while PAE is disabled\n");
> + inject_gp(vcpu);
> + return;
> + }
> + guest_cs_ar = vmcs_read32(GUEST_CS_AR_BYTES);
> + if (guest_cs_ar & SEGMENT_AR_L_MASK) {
> + printk("set_cr0: #GP, start paging in "
> + "long mode while CS.L == 1\n");
> + inject_gp(vcpu);
> + return;
> +
> + }
> + guest_tr_ar = vmcs_read32(GUEST_TR_AR_BYTES);
> + if ((guest_tr_ar & AR_TYPE_MASK) != AR_TYPE_BUSY_64_TSS) {
> + printk("%s: tss fixup for long mode. \n",
> + __FUNCTION__);
> + vmcs_write32(GUEST_TR_AR_BYTES,
> + (guest_tr_ar & ~AR_TYPE_MASK) |
> + AR_TYPE_BUSY_64_TSS);
> + }
> + vcpu->shadow_efer |= EFER_LMA;
> + find_msr_entry(vcpu, MSR_EFER)->data |=
> + EFER_LMA | EFER_LME;
> + vmcs_write32(VM_ENTRY_CONTROLS,
> + vmcs_read32(VM_ENTRY_CONTROLS) |
> + VM_ENTRY_CONTROLS_IA32E_MASK);
> +
> + } else
> +#endif
> + if (is_pae() &&
> + pdptrs_have_reserved_bits_set(vcpu, vcpu->cr3)) {
> + printk("set_cr0: #GP, pdptrs reserved bits\n");
> + inject_gp(vcpu);
> + return;
> + }
> +
> + }
> +
> + __set_cr0(vcpu, cr0);
> + kvm_mmu_reset_context(vcpu);
> + return;
> +}

This function is a little too complex to read. Can you split it up
into smaller functions?

> + } else
> + printk("lmsw: unexpected\n");

Make sure that all printk have KERN_* level in them.

> +
> + #define LMSW_GUEST_MASK 0x0eULL

Don't indent macro definition. Normally, these should to the top of your
file.

> +static long kvm_dev_ioctl(struct file *filp,
> + unsigned int ioctl, unsigned long arg)
> +{
> + struct kvm *kvm = filp->private_data;
> + int r = -EINVAL;
> +
> + switch (ioctl) {
> + default:
> + ;
> + }
> +out:
> + return r;
> +}

Huh? Just leave out stuff like this. If the ioctl function is introduced
in a later patch, you can still add the whole function there.

Arnd <><
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