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Re: [Qemu-devel] [PATCH v2 for-2.0] target-i386: x86_cpu_get_phys_page_d
From: |
Luiz Capitulino |
Subject: |
Re: [Qemu-devel] [PATCH v2 for-2.0] target-i386: x86_cpu_get_phys_page_debug(): support 1GB page translation |
Date: |
Thu, 27 Mar 2014 13:48:08 -0400 |
On Wed, 19 Mar 2014 17:03:53 -0400
Luiz Capitulino <address@hidden> wrote:
> 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.
Peter, can you pick up this one please?
>
> Signed-off-by: Luiz capitulino <address@hidden>
> ---
>
> - 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;