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Re: Xen 3.3: Problem HVM guest

Christoph Egger wrote:


When launching a HVM guest, the process hangs and does not even block any xmlrpc communication, there's a significant system slowdown until reboot.

I finally indentified the place of hang. It is in the xentools33 package
in ${WRKSRC}/libxc/xc_hvm_build.c , function setup_guest().

At the end of setup_guest(), there's this junk of code:

/* Insert JMP <rel32> instruction at address 0x0 to reach entry point. */
    entry_eip = elf_uval(&elf, elf.ehdr, e_entry);
    if ( entry_eip != 0 )    {
        char *page0 = xc_map_foreign_range(
            xc_handle, dom, PAGE_SIZE, PROT_READ | PROT_WRITE, 0);
        if ( page0 == NULL )
            goto error_out;
        page0[0] = 0xe9;               <------------ "hang"
        *(uint32_t *)&page0[1] = entry_eip - 5;
        munmap(page0, PAGE_SIZE);

The "hang" happens when executing page0[0] = 0xe9;

I'm CC this to tech-kern, because I'm not sure if this is a bug in xentools or if I found a UVM/pmap bug.

Here is an URL to the diff where this hunk has been added including the commit log:


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