Hi Kazu,
Thanks for the review.
On 02/21/2019 09:05 PM, Kazuhito Hagio wrote:
Hi Bhupesh,
-----Original Message-----
ARMv8.2-LPA architecture extension (if available on underlying hardware)
can support 52-bit physical addresses, while the kernel virtual
addresses remain 48-bit.
This patch is in accordance with ARMv8 Architecture Reference Manual
version D.a
Make sure that we read the 52-bit PA address capability from
'MAX_PHYSMEM_BITS' variable (if available in vmcoreinfo) and
accordingly change the pte_to_phy() mask values and also traverse
the page-table walk accordingly.
Also make sure that it works well for the existing 48-bit PA address
platforms and also on environments which use newer kernels with 52-bit
PA support but hardware which is not ARM8.2-LPA compliant.
I have sent a kernel patch upstream to add 'MAX_PHYSMEM_BITS' to
vmcoreinfo for arm64 (see [0]).
[0]. http://lists.infradead.org/pipermail/kexec/2019-February/022411.html
Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
This patch looks good to me.
For two slight things below, I will remove them when merging.
+/*
+ * Size mapped by an entry at level n ( 0 <= n <= 3)
+ * We map (PAGE_SHIFT - 3) at all translation levels and PAGE_SHIFT bits
+ * in the final page. The maximum number of translation levels supported by
+ * the architecture is 4. Hence, starting at at level n, we have further
+ * ((4 - n) - 1) levels of translation excluding the offset within the page.
+ * So, the total number of bits mapped by an entry at level n is :
+ *
+ * ((4 - n) - 1) * (PAGE_SHIFT - 3) + PAGE_SHIFT
+ *
+ * Rearranging it a bit we get :
+ * (4 - n) * (PAGE_SHIFT - 3) + 3
+ */
Will remove this comment.
Ok.
+#define pmd_offset_pgtbl_lvl_2(dir, vaddr) ((pmd_t *)dir)
+#define pmd_offset_pgtbl_lvl_3(dir, vaddr) (pud_page_paddr((*(dir))) + pmd_index(vaddr) * sizeof(pmd_t))
Will remove these two macros not in use.
Ok.
And, as I said on another thread, I'm thinking to merge the following
patch after your patch 1/2, it tested OK with 48-bit and 52-bit PA
without NUMBER(MAX_PHYSMEM_BITS) in vmcoreinfo.
Do you think of any case that this will not work well?
diff --git a/arch/arm64.c b/arch/arm64.c
index 29247a7..c7e60e0 100644
--- a/arch/arm64.c
+++ b/arch/arm64.c
@@ -127,6 +127,9 @@ typedef unsigned long pgdval_t;
*/
#define SECTIONS_SIZE_BITS 30
+#define _MAX_PHYSMEM_BITS_48 48
+#define _MAX_PHYSMEM_BITS_52 52
+
/*
* Hardware page table definitions.
*
@@ -402,17 +405,27 @@ get_stext_symbol(void)
return(found ? kallsym : FALSE);
}
+static int
+set_max_physmem_bits_arm64(void)
+{
+ long array_len = ARRAY_LENGTH(mem_section);
+
+ info->max_physmem_bits = _MAX_PHYSMEM_BITS_48;
+ if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME()))
+ || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT())))
+ return TRUE;
+
+ info->max_physmem_bits = _MAX_PHYSMEM_BITS_52;
+ if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME()))
+ || (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT())))
+ return TRUE;
+
+ return FALSE;
+}
+
int
get_machdep_info_arm64(void)
{
- /* Determine if the PA address range is 52-bits: ARMv8.2-LPA */
- if (NUMBER(MAX_PHYSMEM_BITS) != NOT_FOUND_NUMBER) {
- info->max_physmem_bits = NUMBER(MAX_PHYSMEM_BITS);
- if (info->max_physmem_bits == 52)
- lpa_52_bit_support_available = 1;
- } else
- info->max_physmem_bits = 48;
-
/* Check if va_bits is still not initialized. If still 0, call
* get_versiondep_info() to initialize the same.
*/
@@ -428,9 +441,24 @@ get_machdep_info_arm64(void)
info->section_size_bits = SECTIONS_SIZE_BITS;
DEBUG_MSG("kimage_voffset : %lx\n", kimage_voffset);
- DEBUG_MSG("max_physmem_bits : %ld\n", info->max_physmem_bits);
DEBUG_MSG("section_size_bits: %ld\n", info->section_size_bits);
+ /* Determine if the PA address range is 52-bits: ARMv8.2-LPA */
+ if (NUMBER(MAX_PHYSMEM_BITS) != NOT_FOUND_NUMBER) {
+ info->max_physmem_bits = NUMBER(MAX_PHYSMEM_BITS);
+ DEBUG_MSG("max_physmem_bits : %ld (vmcoreinfo)\n",
+ info->max_physmem_bits);
+ } else if (set_max_physmem_bits_arm64()) {
+ DEBUG_MSG("max_physmem_bits : %ld (detected)\n",
+ info->max_physmem_bits);
+ } else {
+ ERRMSG("Can't determine max_physmem_bits value\n");
+ return FALSE;
+ }
+
+ if (info->max_physmem_bits == 52)
+ lpa_52_bit_support_available = 1;
+
return TRUE;
}
I have not tested the above suggestion on a real hardware or emulation
model yet, but as we were discussing in the kernel patch review thread
(see [0]), IMO, we don't need to carry the above hoops for
'MAX_PHYSMEM_BITS' calculation in makedumpfile code as it makes the code
less portable for a newer kernel version and also since other user-space
utilities (like crash) also need a mechanism to determine the PA_BITS
supported by the underlying kernel, so we can use the same uniform
method of using an exported 'MAX_PHYSMEM_BITS' value in the vmcoreinfo
so that all user-land applications can use the same.
I think Dave A. (crash utility maintainer) also pointed to a similar
concern in the above thread.
[0]. http://lists.infradead.org/pipermail/kexec/2019-February/022472.html
Thanks,
Bhupesh
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