[Qemu-devel] [PATCH v2 for-2.0] target-i386: x86_cpu_get_phys_page_debug(): support 1GB page translation

[Luiz Capitulino <lcapitulino@redhat.com>]

Linux guests, when using more than 4GB of RAM, may end up using 1GB pages
to store (kernel) data. When this happens, we're unable to debug a running
Linux kernel with GDB:

(gdb) p node_data[0]->node_id
Cannot access memory at address 0xffff88013fffd3a0
(gdb)

GDB returns this error because x86_cpu_get_phys_page_debug() doesn't support
translating 1GB pages in IA-32e paging mode and returns an error to GDB.

This commit adds support for 1GB page translation for IA32e paging.

Signed-off-by: Luiz capitulino <lcapitulino@redhat.com>
---

- I'm proposing this patch for 2.0 because GDB debugging of large Linux
  guests is kind of broken

- Changelog v2:
  - Move PS bit handling to if (env->hflags & HF_LMA_MASK) block
  - Update changelog

 target-i386/helper.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 4f447b8..7cee501 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -941,6 +941,14 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
             pdpe = ldq_phys(cs->as, pdpe_addr);
             if (!(pdpe & PG_PRESENT_MASK))
                 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;
+            }
+
         } else
 #endif
         {
@@ -993,6 +1001,7 @@ 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;
-- 
1.8.3.1