Hello Cliff,
>>From: Cliff Wickman <cpw at sgi.com>
>>
>>Applies to the development branch as of 10/13/2015.
>>Incorporates review 10/22 by kumagai-atsushi.
>>Incorporates review 10/26 by kumagai-atsushi. (arch x86_64-only implementation)
>
>Thanks for your great work.
>I don't want to delay v1.5.9 release anymore, I'll merge this patch
>into v1.6.0.
Now I'm testing for v1.6.0 release, I found that this feature
will be disabled on some environments.
[skip to find_vmemmap_x86_64()]
>>+/*
>>+ * Scan the kernel page table for the pfn's of the page structs
>>+ * Place them in array gvmem_pfns[nr_gvmem_pfns]
>>+ */
>>+int
>>+find_vmemmap_x86_64()
>>+{
>>+ int i;
>>+ int pgd_index, pud_index;
>>+ int start_range = 1;
>>+ int num_pmds=0, num_pmds_valid=0;
>>+ int break_in_valids, break_after_invalids;
>>+ int do_break, done = 0;
>>+ int last_valid=0, last_invalid=0;
>>+ int pagestructsize, structsperhpage, hugepagesize;
>>+ long page_structs_per_pud;
>>+ long num_puds, groups = 0;
>>+ long pgdindex, pudindex, pmdindex;
>>+ long vaddr, vaddr_base;
>>+ long rep_pfn_start = 0, rep_pfn_end = 0;
>>+ unsigned long init_level4_pgt;
>>+ unsigned long max_paddr, high_pfn;
>>+ unsigned long pgd_addr, pud_addr, pmd_addr;
>>+ unsigned long *pgdp, *pudp, *pmdp;
>>+ unsigned long pud_page[PTRS_PER_PUD];
>>+ unsigned long pmd_page[PTRS_PER_PMD];
>>+ unsigned long vmap_offset_start = 0, vmap_offset_end = 0;
>>+ unsigned long pmd, tpfn;
>>+ unsigned long pvaddr = 0;
>>+ unsigned long data_addr = 0, last_data_addr = 0, start_data_addr = 0;
>>+ /*
>>+ * data_addr is the paddr of the page holding the page structs.
>>+ * We keep lists of contiguous pages and the pfn's that their
>>+ * page structs represent.
>>+ * start_data_addr and last_data_addr mark start/end of those
>>+ * contiguous areas.
>>+ * An area descriptor is vmap start/end pfn and rep start/end
>>+ * of the pfn's represented by the vmap start/end.
>>+ */
>>+ struct vmap_pfns *vmapp, *vmaphead = NULL, *cur, *tail;
>>+
>>+ init_level4_pgt = SYMBOL(init_level4_pgt);
>>+ if (init_level4_pgt == NOT_FOUND_SYMBOL) {
>>+ ERRMSG("init_level4_pgt not found\n");
>>+ return FAILED;
>>+ }
>>+ pagestructsize = size_table.page;
>>+ hugepagesize = PTRS_PER_PMD * info->page_size;
>>+ vaddr_base = info->vmemmap_start;
>>+ vaddr = vaddr_base;
>>+ max_paddr = get_max_paddr();
>>+ /*
>>+ * the page structures are mapped at VMEMMAP_START (info->vmemmap_start)
>>+ * for max_paddr >> 12 page structures
>>+ */
>>+ high_pfn = max_paddr >> 12;
>>+ pgd_index = pgd4_index(vaddr_base);
>>+ pud_index = pud_index(vaddr_base);
>>+ pgd_addr = vaddr_to_paddr(init_level4_pgt); /* address of pgd */
>>+ pgd_addr += pgd_index * sizeof(unsigned long);
>>+ page_structs_per_pud = (PTRS_PER_PUD * PTRS_PER_PMD * info->page_size) /
>>+ pagestructsize;
>>+ num_puds = (high_pfn + page_structs_per_pud - 1) / page_structs_per_pud;
>>+ pvaddr = VMEMMAP_START;
>>+ structsperhpage = hugepagesize / pagestructsize;
>>+
>>+ /* outer loop is for pud entries in the pgd */
>>+ for (pgdindex = 0, pgdp = (unsigned long *)pgd_addr; pgdindex < num_puds;
>>+ pgdindex++, pgdp++) {
>>+ /* read the pgd one word at a time, into pud_addr */
>>+ if (!readmem(PADDR, (unsigned long long)pgdp, (void *)&pud_addr,
>>+ sizeof(unsigned long))) {
>>+ ERRMSG("Can't get pgd entry for slot %d.\n", pgd_index);
>>+ return FAILED;
>>+ }
>>+ /* mask the pgd entry for the address of the pud page */
>>+ pud_addr &= PMASK;
If the pgd entry is null, the code below will try to read 0x0.
This behavior will cause unexpected results, especially if pfn:0 is on
memory hole.
I think null pgd (and pud) entries should be skipped, how about you ?
I would like you to post the bug fix if you have no objection.
Thanks,
Atsushi Kumagai
>>+ /* read the entire pud page */
>>+ if (!readmem(PADDR, (unsigned long long)pud_addr, (void *)pud_page,
>>+ PTRS_PER_PUD * sizeof(unsigned long))) {
>>+ ERRMSG("Can't get pud entry for pgd slot %ld.\n", pgdindex);
>>+ return FAILED;
>>+ }
>>+ /* step thru each pmd address in the pud page */
>>+ /* pudp points to an entry in the pud page */
>>+ for (pudp = (unsigned long *)pud_page, pudindex = 0;
>>+ pudindex < PTRS_PER_PUD; pudindex++, pudp++) {
>>+ pmd_addr = *pudp & PMASK;
>>+ /* read the entire pmd page */
>>+ if (!readmem(PADDR, pmd_addr, (void *)pmd_page,
>>+ PTRS_PER_PMD * sizeof(unsigned long))) {
>>+ ERRMSG("Can't get pud entry for slot %ld.\n", pudindex);
>>+ return FAILED;
>>+ }
>>+ /* pmdp points to an entry in the pmd */
>>+ for (pmdp = (unsigned long *)pmd_page, pmdindex = 0;
>>+ pmdindex < PTRS_PER_PMD; pmdindex++, pmdp++) {
>>+ /* linear page position in this page table: */
>>+ pmd = *pmdp;
>>+ num_pmds++;
>>+ tpfn = (pvaddr - VMEMMAP_START) /
>>+ pagestructsize;
>>+ if (tpfn >= high_pfn) {
>>+ done = 1;
>>+ break;
>>+ }
>>+ /*
>>+ * vmap_offset_start:
>>+ * Starting logical position in the
>>+ * vmemmap array for the group stays
>>+ * constant until a hole in the table
>>+ * or a break in contiguousness.
>>+ */
>>+
>>+ /*
>>+ * Ending logical position in the
>>+ * vmemmap array:
>>+ */
>>+ vmap_offset_end += hugepagesize;
>>+ do_break = 0;
>>+ break_in_valids = 0;
>>+ break_after_invalids = 0;
>>+ /*
>>+ * We want breaks either when:
>>+ * - we hit a hole (invalid)
>>+ * - we discontiguous page is a string of valids
>>+ */
>>+ if (pmd) {
>>+ data_addr = (pmd & PMASK);
>>+ if (start_range) {
>>+ /* first-time kludge */
>>+ start_data_addr = data_addr;
>>+ last_data_addr = start_data_addr
>>+ - hugepagesize;
>>+ start_range = 0;
>>+ }
>>+ if (last_invalid) {
>>+ /* end of a hole */
>>+ start_data_addr = data_addr;
>>+ last_data_addr = start_data_addr
>>+ - hugepagesize;
>>+ /* trigger update of offset */
>>+ do_break = 1;
>>+ }
>>+ last_valid = 1;
>>+ last_invalid = 0;
>>+ /*
>>+ * we have a gap in physical
>>+ * contiguousness in the table.
>>+ */
>>+ /* ?? consecutive holes will have
>>+ same data_addr */
>>+ if (data_addr !=
>>+ last_data_addr + hugepagesize) {
>>+ do_break = 1;
>>+ break_in_valids = 1;
>>+ }
>>+ DEBUG_MSG("valid: pud %ld pmd %ld pfn %#lx"
>>+ " pvaddr %#lx pfns %#lx-%lx"
>>+ " start %#lx end %#lx\n",
>>+ pudindex, pmdindex,
>>+ data_addr >> 12,
>>+ pvaddr, tpfn,
>>+ tpfn + structsperhpage - 1,
>>+ vmap_offset_start,
>>+ vmap_offset_end);
>>+ num_pmds_valid++;
>>+ if (!(pmd & _PAGE_PSE)) {
>>+ printf("vmemmap pmd not huge, abort\n");
>>+ return FAILED;
>>+ }
>>+ } else {
>>+ if (last_valid) {
>>+ /* this a hole after some valids */
>>+ do_break = 1;
>>+ break_in_valids = 1;
>>+ break_after_invalids = 0;
>>+ }
>>+ last_valid = 0;
>>+ last_invalid = 1;
>>+ /*
>>+ * There are holes in this sparsely
>>+ * populated table; they are 2MB gaps
>>+ * represented by null pmd entries.
>>+ */
>>+ DEBUG_MSG("invalid: pud %ld pmd %ld %#lx"
>>+ " pfns %#lx-%lx start %#lx end"
>>+ " %#lx\n", pudindex, pmdindex,
>>+ pvaddr, tpfn,
>>+ tpfn + structsperhpage - 1,
>>+ vmap_offset_start,
>>+ vmap_offset_end);
>>+ }
>>+ if (do_break) {
>>+ /* The end of a hole is not summarized.
>>+ * It must be the start of a hole or
>>+ * hitting a discontiguous series.
>>+ */
>>+ if (break_in_valids || break_after_invalids) {
>>+ /*
>>+ * calculate that pfns
>>+ * represented by the current
>>+ * offset in the vmemmap.
>>+ */
>>+ /* page struct even partly on this page */
>>+ rep_pfn_start = vmap_offset_start /
>>+ pagestructsize;
>>+ /* ending page struct entirely on
>>+ this page */
>>+ rep_pfn_end = ((vmap_offset_end -
>>+ hugepagesize) / pagestructsize);
>>+ DEBUG_MSG("vmap pfns %#lx-%lx "
>>+ "represent pfns %#lx-%lx\n\n",
>>+ start_data_addr >> PAGESHIFT(),
>>+ last_data_addr >> PAGESHIFT(),
>>+ rep_pfn_start, rep_pfn_end);
>>+ groups++;
>>+ vmapp = (struct vmap_pfns *)malloc(
>>+ sizeof(struct vmap_pfns));
>>+ /* pfn of this 2MB page of page structs */
>>+ vmapp->vmap_pfn_start = start_data_addr
>>+ >> PTE_SHIFT;
>>+ vmapp->vmap_pfn_end = last_data_addr
>>+ >> PTE_SHIFT;
>>+ /* these (start/end) are literal pfns
>>+ * on this page, not start and end+1 */
>>+ vmapp->rep_pfn_start = rep_pfn_start;
>>+ vmapp->rep_pfn_end = rep_pfn_end;
>>+
>>+ if (!vmaphead) {
>>+ vmaphead = vmapp;
>>+ vmapp->next = vmapp;
>>+ vmapp->prev = vmapp;
>>+ } else {
>>+ tail = vmaphead->prev;
>>+ vmaphead->prev = vmapp;
>>+ tail->next = vmapp;
>>+ vmapp->next = vmaphead;
>>+ vmapp->prev = tail;
>>+ }
>>+ }
>>+
>>+ /* update logical position at every break */
>>+ vmap_offset_start =
>>+ vmap_offset_end - hugepagesize;
>>+ start_data_addr = data_addr;
>>+ }
>>+
>>+ last_data_addr = data_addr;
>>+ pvaddr += hugepagesize;
>>+ /*
>>+ * pvaddr is current virtual address
>>+ * eg 0xffffea0004200000 if
>>+ * vmap_offset_start is 4200000
>>+ */
>>+ }
>>+ }
>>+ tpfn = (pvaddr - VMEMMAP_START) / pagestructsize;
>>+ if (tpfn >= high_pfn) {
>>+ done = 1;
>>+ break;
>>+ }
>>+ }
>>+ rep_pfn_start = vmap_offset_start / pagestructsize;
>>+ rep_pfn_end = (vmap_offset_end - hugepagesize) / pagestructsize;
>>+ DEBUG_MSG("vmap pfns %#lx-%lx represent pfns %#lx-%lx\n\n",
>>+ start_data_addr >> PAGESHIFT(), last_data_addr >> PAGESHIFT(),
>>+ rep_pfn_start, rep_pfn_end);
>>+ groups++;
>>+ vmapp = (struct vmap_pfns *)malloc(sizeof(struct vmap_pfns));
>>+ vmapp->vmap_pfn_start = start_data_addr >> PTE_SHIFT;
>>+ vmapp->vmap_pfn_end = last_data_addr >> PTE_SHIFT;
>>+ vmapp->rep_pfn_start = rep_pfn_start;
>>+ vmapp->rep_pfn_end = rep_pfn_end;
>>+ if (!vmaphead) {
>>+ vmaphead = vmapp;
>>+ vmapp->next = vmapp;
>>+ vmapp->prev = vmapp;
>>+ } else {
>>+ tail = vmaphead->prev;
>>+ vmaphead->prev = vmapp;
>>+ tail->next = vmapp;
>>+ vmapp->next = vmaphead;
>>+ vmapp->prev = tail;
>>+ }
>>+ DEBUG_MSG("num_pmds: %d num_pmds_valid %d\n", num_pmds, num_pmds_valid);
>>+
>>+ /* transfer the linked list to an array */
>>+ cur = vmaphead;
>>+ gvmem_pfns = (struct vmap_pfns *)malloc(sizeof(struct vmap_pfns) * groups);
>>+ i = 0;
>>+ do {
>>+ vmapp = gvmem_pfns + i;
>>+ vmapp->vmap_pfn_start = cur->vmap_pfn_start;
>>+ vmapp->vmap_pfn_end = cur->vmap_pfn_end;
>>+ vmapp->rep_pfn_start = cur->rep_pfn_start;
>>+ vmapp->rep_pfn_end = cur->rep_pfn_end;
>>+ cur = cur->next;
>>+ free(cur->prev);
>>+ i++;
>>+ } while (cur != vmaphead);
>>+ nr_gvmem_pfns = i;
>>+ return COMPLETED;
>>+}
>>+
>> #endif /* x86_64 */
>>
>
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