On Mon, Aug 02, 2010 at 09:55:42AM -0400, Avi Kivity wrote:
> On 08/02/2010 04:33 PM, Joerg Roedel wrote:
> > +static void test_mode_switch(struct test *test)
> > +{
> > + asm volatile(" cli\n"
> > + " ljmp *1f\n" /* jump to 32-bit code segment */
> > + "1:\n"
> > + " .long 2f\n"
> > + " .long 40\n"
> > + ".code32\n"
> > + "2:\n"
> > + " movl %%cr0, %%eax\n"
> > + " btcl $31, %%eax\n" /* clear PG */
> > + " movl %%eax, %%cr0\n"
> > + " movl $0xc0000080, %%ecx\n" /* EFER */
> > + " rdmsr\n"
> > + " btcl $8, %%eax\n" /* clear LME */
> > + " wrmsr\n"
> > + " movl %%cr4, %%eax\n"
> > + " btcl $5, %%eax\n" /* clear PAE */
> > + " movl %%eax, %%cr4\n"
> > + " movw $64, %%ax\n"
> > + " movw %%ax, %%ds\n"
> > + " ljmpl $56, $3f\n" /* jump to 16 bit protected-mode */
> > + ".code16\n"
> > + "3:\n"
> > + " movl %%cr0, %%eax\n"
> > + " btcl $0, %%eax\n" /* clear PE */
> > + " movl %%eax, %%cr0\n"
> > + " ljmpl $0, $4f\n" /* jump to real-mode */
> > + "4:\n"
> > + " vmmcall\n"
> > + " movl %%cr0, %%eax\n"
> > + " btsl $0, %%eax\n" /* set PE */
> > + " movl %%eax, %%cr0\n"
> > + " ljmpl $40, $5f\n" /* back to protected mode */
> > + ".code32\n"
> > + "5:\n"
> > + " movl %%cr4, %%eax\n"
> > + " btsl $5, %%eax\n" /* set PAE */
> > + " movl %%eax, %%cr4\n"
> > + " movl $0xc0000080, %%ecx\n" /* EFER */
> > + " rdmsr\n"
> > + " btsl $8, %%eax\n" /* set LME */
> > + " wrmsr\n"
> > + " movl %%cr0, %%eax\n"
> > + " btsl $31, %%eax\n" /* set PG */
> > + " movl %%eax, %%cr0\n"
> > + " ljmpl $8, $6f\n" /* back to long mode */
> > + ".code64\n\t"
> > + "6:\n"
> > + " vmmcall\n"
> > + ::: "rax", "rbx", "rcx", "rdx", "memory");
> > +}
> > +
>
> What is this testing exactly? There is no svm function directly
> associated with mode switch. In fact, most L1s will intercept cr and
> efer access and emulate the mode switch, rather than letting L2 perform
> the mode switch directly.
This is testing the failure case without the nested-svm efer patch I
submitted last week. The sequence above (which switches from long mode
to real mode and back to long mode) fails without this patch.
Joerg
--
AMD Operating System Research Center
Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
