On Tue, 18 Mar 2014 08:19:52 +0100
Jan Kiszka <jan.kis...@siemens.com> wrote:
> On 2014-03-18 02:54, Luiz Capitulino wrote:
> > If you start a Linux guest with more than 4GB of memory and try to look at a
> > memory address, you will get an error from gdb:
> >
> > (gdb) p node_data[0]->node_id
> > Cannot access memory at address 0xffff88013fffd3a0
> > (gdb)
>
> I suppose this is x86-64, not 32-bit with PTE, right?
Right.
>
> >
> > I debugged this down to x86_cpu_get_phys_page_debug(), it doesn't handle the
> > case where the PDPTE has the PS bit set (although I didn't check where Linux
> > sets that bit). This commit adds the PS bit handling, which fixes the
> > problem
> > for me.
> >
> > Signed-off-by: Luiz capitulino <lcapitul...@redhat.com>
> > ---
> >
> > Two observations:
> >
> > 1. This bug has always existed, so it's not a regression, so I'm not sure
> > it's worth it to fix for 2.0
> >
> > 2. I'm not familiar with every detail of x86_cpu_get_phys_page_debug(),
> > so I'm not completely sure this is the right thing to do
> >
> > target-i386/helper.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/target-i386/helper.c b/target-i386/helper.c
> > index 4f447b8..9b7803f 100644
> > --- a/target-i386/helper.c
> > +++ b/target-i386/helper.c
> > @@ -951,6 +951,13 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr
> > addr)
> > return -1;
> > }
> >
> > + if (pdpe & PG_PSE_MASK) {
> > + page_size = 1024 * 1024 * 1024;
> > + pte = pdpe & ~( (page_size - 1) & ~0xfff);
> > + pte &= ~(PG_NX_MASK | PG_HI_USER_MASK);
> > + goto out;
> > + }
>
> Does this also apply if we are not in long mode?
>
> I'll check this more carefully later.
>
> Jan
>
> > +
> > pde_addr = ((pdpe & ~0xfff & ~(PG_NX_MASK | PG_HI_USER_MASK)) +
> > (((addr >> 21) & 0x1ff) << 3)) & env->a20_mask;
> > pde = ldq_phys(cs->as, pde_addr);
> > @@ -993,6 +1000,7 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr
> > addr)
> > pte = pte & env->a20_mask;
> > }
> >
> > +out:
> > page_offset = (addr & TARGET_PAGE_MASK) & (page_size - 1);
> > paddr = (pte & TARGET_PAGE_MASK) + page_offset;
> > return paddr;
> >
>
