# Ring-0 stubs — AMD64 System V ABI.
# Args: rdi, rsi, rdx, rcx, r8, r9.  Return: rax (rdx:rax for 128-bit).
# All of these fault at CPL > 0 (#GP or #UD).

.text

# read_cr3() -> u64
# returns the physical address of the host PML4.
.globl read_cr3
read_cr3:
    movq %cr3, %rax
    ret

# write_cr3(cr3: u64)
# flushes all non-global TLB entries
.globl write_cr3
write_cr3:
    movq %rdi, %cr3
    ret

# vmload(vmcb_pa: u64)
# AMD SVM: loads guest state from the VMCB at the given physical address
.globl vmload
vmload:
    movq %rdi, %rax
    vmload %rax
    ret

# vmsave(vmcb_pa: u64)
# AMD SVM: saves guest state back to the VMCB at the given physical address
.globl vmsave
vmsave:
    movq %rdi, %rax
    vmsave %rax
    ret

# vmrun(vmcb_pa: u64)
# AMD SVM: enters the guest.  Does not return until a #VMEXIT
.globl vmrun
vmrun:
    movq %rdi, %rax
    vmrun %rax
    ret

# rdmsr(msr: u32) -> u64
# Reads the MSR number in edi; returns edx:eax packed into rax
.globl rdmsr
rdmsr:
    movl %edi, %ecx
    rdmsr
    shlq $32, %rdx
    orq  %rdx, %rax
    ret

# wrmsr(msr: u32, val: u64)
# msr in edi, 64-bit value in rsi
.globl wrmsr
wrmsr:
    movl  %edi, %ecx
    movl  %esi, %eax        # low 32 bits
    movq  %rsi, %rdx
    shrq  $32,  %rdx        # high 32 bits
    wrmsr
    ret