Re: R/W HG memory mappings with kvm?

[Tsuyoshi Ozawa <ozadev@t-oza.net>]

Hello,

>>  Sorry about that. The issue is the BUG in gfn_to_pgn where the pfn is
>>  not calculated correctly after looking up the vma.

>>  I still don't see how to get the physical address from the vma, since
>>  vm_pgoff is zero, and the vm_ops are not filled. The vma does not seem
>>  to store the physical base address.

> So it seems the only place the pfns are stored are in the ptes themselves. Is there an API to recover the ptes from a virtual address? We could use that instead.

I'm also trying to share H/G memory with another solution -
by overwriting shadow page table.

It seems that gfn_to_pfn is the key function which associate
guest memoy with host memory. So I changed gfn_to_pfn
as follows:

pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
{
    ...
    } else
        if ( shared_gfn && shared_gfn == gfn ){
            return shared_pfn;  // return pfn which is wanted to share
        }else {
            pfn = page_to_pfn(page[0]);
        }
    }
    ...
}

Here, shared_gfn is registered by walking soft mmu with gva.
And shared_pfn is the page frame number which is hostside.
By rewriting adobe, kvm is foxed and make up new shadow
page table with new mapping after zap all pages.

But I failed to share the memory. Do I have any misunderstanding?

Regards,
Tsuyoshi Ozawa