Re: [PATCH 1/5] KVM paravirt_ops core infrastructure

Dor Laor
2007-06-26T08:04:27Z

...
+static __init struct kvm_paravirt_state *paravirt_alloc_state(void)
+{
+ struct kvm_paravirt_state *state;
+
+ state = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!state)
+ goto err;
+
+ state->vmca = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!state->vmca)
+ goto err;
+
+ /* FIXME: what do I need for this to be executable on 64 bit? */
+ state->hypercall = (void *)get_zeroed_page(GFP_KERNEL);

Why do you alloc a page for the hypercall instead of using Ingo's code
below? This way it can work for 64 bit too.

Ingo's code:
/*
* This is the vm-syscall address - to be patched by the host to
* VMCALL (Intel) or VMMCALL (AMD), depending on the CPU model:
*/
asm (
" .globl hypercall_addr \n"
" .align 4 \n"
" hypercall_addr: \n"
" movl $-38, %eax \n"
" ret \n"
);
extern unsigned char hypercall_addr[6];

And use it this way: (I used vmalloc_to_page since its compiles as a
module)
hypercall_addr_page = vmalloc_to_page(hypercall_addr);
para_state->hypercall_gpa = page_to_pfn(hypercall_addr_page) <<
PAGE_SHIFT |
offset_in_page(hypercall_addr);

Regards,
Dor.