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?
>
> 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;
>
--
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Corporate Competence Center Embedded Linux
