Il 18/03/2014 08:19, Jan Kiszka ha scritto:
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
Sure, why not?
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?
No, it doesn't. The only valid bits in a PAE PDPTE are P, PWT and PCD.
Bit 7 (PS) is reserved.
Paolo
