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

Anthony Liguori
2007-06-26T11:56:10Z

Dor Laor wrote:
> ...
> +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.
>

The current patch queue uses data in the text segment but it makes sure
that it has a proper page.

Regards,

Anthony Liguori

> 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.