[RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA
piliu
piliu at redhat.com
Thu Jan 14 05:03:23 EST 2021
On 1/14/21 4:25 PM, kazuhito.hagio at gmail.com wrote:
> From: Kazuhito Hagio <k-hagio-ab at nec.com>
>
> Based on Bhupesh's patch and contains Pingfan's idea.
>
> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> ---
> arch/arm64.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> makedumpfile.c | 2 ++
> makedumpfile.h | 1 +
> 3 files changed, 83 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm64.c b/arch/arm64.c
> index 61ec89a..4ece19d 100644
> --- a/arch/arm64.c
> +++ b/arch/arm64.c
> @@ -47,6 +47,8 @@ typedef struct {
> static int lpa_52_bit_support_available;
> static int pgtable_level;
> static int va_bits;
> +static int vabits_actual;
> +static int flipped_va;
> static unsigned long kimage_voffset;
>
> #define SZ_4K 4096
> @@ -58,7 +60,6 @@ static unsigned long kimage_voffset;
> #define PAGE_OFFSET_42 ((0xffffffffffffffffUL) << 42)
> #define PAGE_OFFSET_47 ((0xffffffffffffffffUL) << 47)
> #define PAGE_OFFSET_48 ((0xffffffffffffffffUL) << 48)
> -#define PAGE_OFFSET_52 ((0xffffffffffffffffUL) << 52)
>
> #define pgd_val(x) ((x).pgd)
> #define pud_val(x) (pgd_val((x).pgd))
> @@ -218,12 +219,20 @@ pmd_page_paddr(pmd_t pmd)
> #define pte_index(vaddr) (((vaddr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))
> #define pte_offset(dir, vaddr) (pmd_page_paddr((*dir)) + pte_index(vaddr) * sizeof(pte_t))
>
> +/*
> + * The linear kernel range starts at the bottom of the virtual address
> + * space. Testing the top bit for the start of the region is a
> + * sufficient check and avoids having to worry about the tag.
> + */
> +#define is_linear_addr(addr) (flipped_va ? \
> + (!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))) : \
> + (!!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))))
> +
> static unsigned long long
> __pa(unsigned long vaddr)
> {
> - if (kimage_voffset == NOT_FOUND_NUMBER ||
> - (vaddr >= PAGE_OFFSET))
> - return (vaddr - PAGE_OFFSET + info->phys_base);
> + if (kimage_voffset == NOT_FOUND_NUMBER || is_linear_addr(vaddr))
> + return ((vaddr & ~PAGE_OFFSET) + info->phys_base);
> else
> return (vaddr - kimage_voffset);
> }
> @@ -253,6 +262,7 @@ static int calculate_plat_config(void)
> (PAGESIZE() == SZ_64K && va_bits == 42)) {
> pgtable_level = 2;
> } else if ((PAGESIZE() == SZ_64K && va_bits == 48) ||
> + (PAGESIZE() == SZ_64K && va_bits == 52) ||
> (PAGESIZE() == SZ_4K && va_bits == 39) ||
> (PAGESIZE() == SZ_16K && va_bits == 47)) {
> pgtable_level = 3;
> @@ -263,6 +273,7 @@ static int calculate_plat_config(void)
> PAGESIZE(), va_bits);
> return FALSE;
> }
> + DEBUG_MSG("pgtable_level: %d\n", pgtable_level);
>
> return TRUE;
> }
> @@ -383,22 +394,54 @@ get_va_bits_from_stext_arm64(void)
> return TRUE;
> }
>
> +static void
> +get_page_offset_arm64(void)
> +{
> + ulong page_end;
> + int vabits_min;
> +
> + /*
> + * See arch/arm64/include/asm/memory.h for more details of
> + * the PAGE_OFFSET calculation.
> + */
> + vabits_min = (va_bits > 48) ? 48 : va_bits;
> + page_end = -(1UL << (vabits_min - 1));
> +
> + if (SYMBOL(_stext) > page_end) {
> + flipped_va = TRUE;
> + info->page_offset = -(1UL << vabits_actual);
> + } else {
> + flipped_va = FALSE;
> + info->page_offset = -(1UL << (vabits_actual - 1));
> + }
> +
> + DEBUG_MSG("page_offset : %lx (from page_end check)\n",
> + info->page_offset);
> +}
> +
> int
> get_machdep_info_arm64(void)
> {
> + /* Check if va_bits is still not initialized. If still 0, call
> + * get_versiondep_info() to initialize the same.
> + */
> + if (!va_bits)
> + get_versiondep_info_arm64();
> +
> /* 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);
> if (info->max_physmem_bits == 52)
> lpa_52_bit_support_available = 1;
> - } else
> - info->max_physmem_bits = 48;
> + } else {
> + if (va_bits == 52)
> + info->max_physmem_bits = 52; /* just guess */
> + 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.
> - */
> - if (!va_bits)
> - get_versiondep_info_arm64();
> + DEBUG_MSG("max_physmem_bits : %ld (guess)\n", info->max_physmem_bits);
> + }
>
> if (!calculate_plat_config()) {
> ERRMSG("Can't determine platform config values\n");
> @@ -409,7 +452,6 @@ 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);
>
> return TRUE;
> @@ -444,10 +486,33 @@ get_versiondep_info_arm64(void)
> return FALSE;
> }
>
> - info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> + /*
> + * See TCR_EL1, Translation Control Register (EL1) register
> + * description in the ARMv8 Architecture Reference Manual.
> + * Basically, we can use the TCR_EL1.T1SZ
> + * value to determine the virtual addressing range supported
> + * in the kernel-space (i.e. vabits_actual) since Linux 5.9.
> + */
> + if (NUMBER(TCR_EL1_T1SZ) != NOT_FOUND_NUMBER) {
> + vabits_actual = 64 - NUMBER(TCR_EL1_T1SZ);
> + DEBUG_MSG("vabits_actual : %d (vmcoreinfo)\n", vabits_actual);
> + } else if ((va_bits == 52) && (SYMBOL(mem_section) != NOT_FOUND_SYMBOL)) {
> + /*
> + * Linux 5.4 through 5.10 have the following linear space:
> + * 48-bit: 0xffff000000000000 - 0xffff7fffffffffff
> + * 58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
> + */
> + if (SYMBOL(mem_section) & (1UL << (52 - 1)))
Sorry but I do not think any SYMBOL(x) is inside the range of linear
mapping address. All of them should be beyond kimage_vaddr.
Having vabits_actual is introduced and precise to resolve
is_lm_address(), but if it is not available, could we survive?
_PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
Translating into numbers:
0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 <
0xffff800000000000
Refer to linux/Documentation/arm64/memory.rst, the line
ffffa00010000000 fffff81ffffeffff ~88TB vmalloc
It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).
So is_lm_address() can looks like
if (addr > _PAGE_END(48)), it is kimage
else, it is linear mapping
So even more aggressive, we can exclude the need of vabits_actual
totally in this patch.
Thanks,
Pingfan
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