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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 5/6] xen: modify page table construction
On Thu, Feb 11, 2016 at 03:35:45PM +0100, Juergen Gross wrote:
> On 11/02/16 13:47, Daniel Kiper wrote:
> > On Thu, Feb 11, 2016 at 08:53:25AM +0100, Juergen Gross wrote:
> >> Modify the page table construction to allow multiple virtual regions
> >> to be mapped. This is done as preparation for removing the p2m list
> >> from the initial kernel mapping in order to support huge pv domains.
> >>
> >> This allows a cleaner approach for mapping the relocator page by
> >> using this capability.
> >>
> >> The interface to the assembler level of the relocator has to be changed
> >> in order to be able to process multiple page table areas.
> >
> > I hope that older kernels could be loaded as is and everything works as
> > expected.
>
> See Patch 0/6. I have tested old kernels, too.
That is great! I just wanted to be sure.
> >> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >> ---
> >> grub-core/lib/i386/xen/relocator.S | 47 +++---
> >> grub-core/lib/x86_64/xen/relocator.S | 44 +++--
> >> grub-core/lib/xen/relocator.c | 22 ++-
> >> grub-core/loader/i386/xen.c | 313
> >> +++++++++++++++++++++++------------
> >> include/grub/xen/relocator.h | 6 +-
> >> 5 files changed, 277 insertions(+), 155 deletions(-)
> >>
> >> diff --git a/grub-core/lib/i386/xen/relocator.S
> >> b/grub-core/lib/i386/xen/relocator.S
> >> index 694a54c..c23b405 100644
> >> --- a/grub-core/lib/i386/xen/relocator.S
> >> +++ b/grub-core/lib/i386/xen/relocator.S
> >> @@ -50,41 +50,45 @@ VARIABLE(grub_relocator_xen_remapper_map_high)
> >> jmp *%ebx
> >>
> >> LOCAL(cont):
> >> - xorl %eax, %eax
> >> - movl %eax, %ebp
> >> + /* mov imm32, %eax */
> >> + .byte 0xb8
> >> +VARIABLE(grub_relocator_xen_paging_areas_addr)
> >> + .long 0
> >> + movl %eax, %ebx
> >> 1:
> >> -
> >> + movl 0(%ebx), %ebp
> >> + movl 4(%ebx), %ecx
> >
> > Oh... No, please use constants not plain numbers and
> > explain in comments what is going on. Otherwise it
> > is unreadable.
>
> Hmm, yes, some comments wouldn't hurt. :-)
> Regarding constants: do you really think I should introduce their
> first usage in this file with my patch?
I would not afraid that. At least in code you change/touch. If you
are not sure please ask maintainer about that.
> >> + testl %ecx, %ecx
> >> + jz 3f
> >> + addl $8, %ebx
> >> + movl %ebx, %esp
> >> +
> >> +2:
> >> + movl %ecx, %edi
> >> /* mov imm32, %eax */
> >> .byte 0xb8
> >> VARIABLE(grub_relocator_xen_mfn_list)
> >> .long 0
> >> - movl %eax, %edi
> >> - movl %ebp, %eax
> >> - movl 0(%edi, %eax, 4), %ecx
> >> -
> >> - /* mov imm32, %ebx */
> >> - .byte 0xbb
> >> -VARIABLE(grub_relocator_xen_paging_start)
> >> - .long 0
> >> - shll $12, %eax
> >> - addl %eax, %ebx
> >> + movl 0(%eax, %ebp, 4), %ecx
> >> + movl %ebp, %ebx
> >> + shll $12, %ebx
> >
> > Ditto.
>
> Look at the removed line above: I just switched register usage.
It does not hurt to change number to constant here too.
> >> movl %ecx, %edx
> >> shll $12, %ecx
> >> shrl $20, %edx
> >> orl $5, %ecx
> >> movl $2, %esi
> >> movl $__HYPERVISOR_update_va_mapping, %eax
> >> - int $0x82
> >> + int $0x82 /* parameters: eax, ebx, ecx, edx, esi */
> >
> > Please use more verbose comments.
>
> :-)
>
> >
> >>
> >> incl %ebp
> >> - /* mov imm32, %ecx */
> >> - .byte 0xb9
> >> -VARIABLE(grub_relocator_xen_paging_size)
> >> - .long 0
> >> - cmpl %ebp, %ecx
> >> + movl %edi, %ecx
> >> +
> >> + loop 2b
> >>
> >> - ja 1b
> >> + mov %esp, %ebx
> >> + jmp 1b
> >>
> >> +3:
> >> /* mov imm32, %ebx */
> >> .byte 0xbb
> >> VARIABLE(grub_relocator_xen_mmu_op_addr)
> >> @@ -102,6 +106,9 @@ VARIABLE(grub_relocator_xen_remap_continue)
> >>
> >> jmp *%eax
> >>
> >> +VARIABLE(grub_relocator_xen_paging_areas)
> >> + .long 0, 0, 0, 0, 0, 0, 0, 0
> >> +
> >> VARIABLE(grub_relocator_xen_mmu_op)
> >> .space 256
> >>
> >> diff --git a/grub-core/lib/x86_64/xen/relocator.S
> >> b/grub-core/lib/x86_64/xen/relocator.S
> >> index 92e9e72..dbb90c7 100644
> >> --- a/grub-core/lib/x86_64/xen/relocator.S
> >> +++ b/grub-core/lib/x86_64/xen/relocator.S
> >
> > Is to possible to split this patch to i386 and x86-64 stuff patches?
>
> I don't think so. The C-part is common and assembler sources must both
> match.
Yep, I am aware of that. However, I was able to that in my patch series.
So, maybe it is possible here. Could you try it?
> >> @@ -50,31 +50,24 @@ VARIABLE(grub_relocator_xen_remapper_map)
> >>
> >> LOCAL(cont):
> >>
> >> - /* mov imm64, %rcx */
> >> - .byte 0x48
> >> - .byte 0xb9
> >> -VARIABLE(grub_relocator_xen_paging_size)
> >> - .quad 0
> >> -
> >> - /* mov imm64, %rax */
> >> - .byte 0x48
> >> - .byte 0xb8
> >> -VARIABLE(grub_relocator_xen_paging_start)
> >> - .quad 0
> >> -
> >> - movq %rax, %r12
> >> -
> >> /* mov imm64, %rax */
> >> .byte 0x48
> >> .byte 0xb8
> >> VARIABLE(grub_relocator_xen_mfn_list)
> >> .quad 0
> >>
> >> - movq %rax, %rsi
> >> + movq %rax, %rbx
> >> + leaq EXT_C(grub_relocator_xen_paging_areas) (%rip), %r8
> >> +
> >> 1:
> >> + movq 0(%r8), %r12
> >> + movq 8(%r8), %rcx
> >
> > Ditto.
> >
> >> + testq %rcx, %rcx
> >> + jz 3f
> >> +2:
> >> movq %r12, %rdi
> >> - movq %rsi, %rbx
> >> - movq 0(%rsi), %rsi
> >> + shlq $12, %rdi
> >> + movq (%rbx, %r12, 8), %rsi
> >
> > Ditto.
> >
> >> shlq $12, %rsi
> >> orq $5, %rsi
> >> movq $2, %rdx
> >> @@ -83,13 +76,15 @@ VARIABLE(grub_relocator_xen_mfn_list)
> >> syscall
> >>
> >> movq %r9, %rcx
> >> - addq $8, %rbx
> >> - addq $4096, %r12
> >> - movq %rbx, %rsi
> >> + incq %r12
> >> +
> >> + loop 2b
> >>
> >> - loop 1b
> >> + addq $16, %r8
> >
> > Ditto.
> >
> >> + jmp 1b
> >>
> >> - leaq LOCAL(mmu_op) (%rip), %rdi
> >> +3:
> >> + leaq EXT_C(grub_relocator_xen_mmu_op) (%rip), %rdi
> >> movq $3, %rsi
> >> movq $0, %rdx
> >> movq $0x7FF0, %r10
> >
> > Ugh... Please fix this too. Probably in separate patch.
>
> I don't mind cleaning the assembler sources by using more comments
> and constants. I just don't think this should be part of this series.
I think that you can safely fix that issue in code you touch. I do not
insist on fixing rest of the code in the same patch. However, it would
be nice if you remove such worst/obvious warts at least at the end of
this patch series.
> >> @@ -104,7 +99,10 @@ VARIABLE(grub_relocator_xen_remap_continue)
> >>
> >> jmp *%rax
> >>
> >> -LOCAL(mmu_op):
> >> +VARIABLE(grub_relocator_xen_paging_areas)
> >> + /* array of start, size pairs, size 0 is end marker */
> >> + .quad 0, 0, 0, 0, 0, 0, 0, 0
> >> +
> >> VARIABLE(grub_relocator_xen_mmu_op)
> >> .space 256
> >>
> >> diff --git a/grub-core/lib/xen/relocator.c b/grub-core/lib/xen/relocator.c
> >> index 8f427d3..bc29055 100644
> >> --- a/grub-core/lib/xen/relocator.c
> >> +++ b/grub-core/lib/xen/relocator.c
> >> @@ -36,15 +36,15 @@ extern grub_uint8_t grub_relocator_xen_remap_end;
> >> extern grub_xen_reg_t grub_relocator_xen_stack;
> >> extern grub_xen_reg_t grub_relocator_xen_start_info;
> >> extern grub_xen_reg_t grub_relocator_xen_entry_point;
> >> -extern grub_xen_reg_t grub_relocator_xen_paging_start;
> >> -extern grub_xen_reg_t grub_relocator_xen_paging_size;
> >> extern grub_xen_reg_t grub_relocator_xen_remapper_virt;
> >> extern grub_xen_reg_t grub_relocator_xen_remapper_virt2;
> >> extern grub_xen_reg_t grub_relocator_xen_remapper_map;
> >> extern grub_xen_reg_t grub_relocator_xen_mfn_list;
> >> +extern grub_xen_reg_t grub_relocator_xen_paging_areas[2 *
> >> XEN_MAX_MAPPINGS];
> >> extern grub_xen_reg_t grub_relocator_xen_remap_continue;
> >> #ifdef __i386__
> >> extern grub_xen_reg_t grub_relocator_xen_mmu_op_addr;
> >> +extern grub_xen_reg_t grub_relocator_xen_paging_areas_addr;
> >> extern grub_xen_reg_t grub_relocator_xen_remapper_map_high;
> >> #endif
> >> extern mmuext_op_t grub_relocator_xen_mmu_op[3];
> >> @@ -61,6 +61,7 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
> >> {
> >> grub_err_t err;
> >> void *relst;
> >> + int i;
> >> grub_relocator_chunk_t ch, ch_tramp;
> >> grub_xen_mfn_t *mfn_list =
> >> (grub_xen_mfn_t *) grub_xen_start_page_addr->mfn_list;
> >> @@ -77,8 +78,11 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
> >> grub_relocator_xen_stack = state.stack;
> >> grub_relocator_xen_start_info = state.start_info;
> >> grub_relocator_xen_entry_point = state.entry_point;
> >> - grub_relocator_xen_paging_start = state.paging_start << 12;
> >> - grub_relocator_xen_paging_size = state.paging_size;
> >> + for (i = 0; i < XEN_MAX_MAPPINGS; i++)
> >> + {
> >> + grub_relocator_xen_paging_areas[2 * i] = state.paging_start[i];
> >> + grub_relocator_xen_paging_areas[2 * i + 1] = state.paging_size[i];
> >
> > Why 2 and 1? Constants?
>
> I guess I should probably define grub_relocator_xen_paging_areas as
> an array of struct { grub_xen_reg_t start; grub_xen_reg_t size; };
Make sense for me.
> >> + }
> >> grub_relocator_xen_remapper_virt = remapper_virt;
> >> grub_relocator_xen_remapper_virt2 = remapper_virt;
> >> grub_relocator_xen_remap_continue = trampoline_virt;
> >> @@ -88,10 +92,12 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
> >> grub_relocator_xen_remapper_map_high = (mfn_list[remapper_pfn] >> 20);
> >> grub_relocator_xen_mmu_op_addr = (char *) &grub_relocator_xen_mmu_op
> >> - (char *) &grub_relocator_xen_remap_start + remapper_virt;
> >> + grub_relocator_xen_paging_areas_addr =
> >> + (char *) &grub_relocator_xen_paging_areas
> >> + - (char *) &grub_relocator_xen_remap_start + remapper_virt;
> >> #endif
> >>
> >> - grub_relocator_xen_mfn_list = state.mfn_list
> >> - + state.paging_start * sizeof (grub_addr_t);
> >> + grub_relocator_xen_mfn_list = state.mfn_list;
> >>
> >> grub_memset (grub_relocator_xen_mmu_op, 0,
> >> sizeof (grub_relocator_xen_mmu_op));
> >> @@ -100,9 +106,9 @@ grub_relocator_xen_boot (struct grub_relocator *rel,
> >> #else
> >> grub_relocator_xen_mmu_op[0].cmd = MMUEXT_PIN_L4_TABLE;
> >> #endif
> >> - grub_relocator_xen_mmu_op[0].arg1.mfn = mfn_list[state.paging_start];
> >> + grub_relocator_xen_mmu_op[0].arg1.mfn = mfn_list[state.paging_start[0]];
> >> grub_relocator_xen_mmu_op[1].cmd = MMUEXT_NEW_BASEPTR;
> >> - grub_relocator_xen_mmu_op[1].arg1.mfn = mfn_list[state.paging_start];
> >> + grub_relocator_xen_mmu_op[1].arg1.mfn = mfn_list[state.paging_start[0]];
> >> grub_relocator_xen_mmu_op[2].cmd = MMUEXT_UNPIN_TABLE;
> >> grub_relocator_xen_mmu_op[2].arg1.mfn =
> >> mfn_list[grub_xen_start_page_addr->pt_base >> 12];
> >> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
> >> index 0f41048..5e10420 100644
> >> --- a/grub-core/loader/i386/xen.c
> >> +++ b/grub-core/loader/i386/xen.c
> >> @@ -42,6 +42,29 @@
> >>
> >> GRUB_MOD_LICENSE ("GPLv3+");
> >>
> >> +#ifdef __x86_64__
> >> +#define NUMBER_OF_LEVELS 4
> >> +#define INTERMEDIATE_OR 7
> >> +#define VIRT_MASK 0x0000ffffffffffffULL
> >> +#else
> >> +#define NUMBER_OF_LEVELS 3
> >> +#define INTERMEDIATE_OR 3
> >> +#define VIRT_MASK 0x00000000ffffffffULL
> >
> > Long expected constants... Nice!
>
> Just to please you. :-)
> They were just moved up some lines as they are used in the new
> structure definitions.
>
> Using constants was unavoidable here. ;-)
Thanks a lot! :-)))
> >> +#endif
> >> +
> >> +struct grub_xen_mapping_lvl {
> >> + grub_uint64_t virt_start;
> >> + grub_uint64_t virt_end;
> >> + grub_uint64_t pfn_start;
> >> + grub_uint64_t n_pt_pages;
> >> +};
> >> +
> >> +struct grub_xen_mapping {
> >> + grub_uint64_t *where;
> >> + struct grub_xen_mapping_lvl area;
> >> + struct grub_xen_mapping_lvl lvls[NUMBER_OF_LEVELS];
> >> +};
> >> +
> >> static struct grub_relocator *relocator = NULL;
> >> static grub_uint64_t max_addr;
> >> static grub_dl_t my_mod;
> >> @@ -56,9 +79,10 @@ static struct grub_relocator_xen_state state;
> >> static grub_xen_mfn_t *virt_mfn_list;
> >> static struct start_info *virt_start_info;
> >> static grub_xen_mfn_t console_pfn;
> >> -static grub_uint64_t *virt_pgtable;
> >> -static grub_uint64_t pgtbl_start;
> >> static grub_uint64_t pgtbl_end;
> >> +static struct grub_xen_mapping mappings[XEN_MAX_MAPPINGS];
> >> +static int n_mappings;
> >> +static struct grub_xen_mapping *map_reloc;
> >>
> >> #define PAGE_SIZE 4096
> >> #define MAX_MODULES (PAGE_SIZE / sizeof (struct xen_multiboot_mod_list))
> >> @@ -75,100 +99,162 @@ page2offset (grub_uint64_t page)
> >> return page << PAGE_SHIFT;
> >> }
> >>
> >> -#ifdef __x86_64__
> >> -#define NUMBER_OF_LEVELS 4
> >> -#define INTERMEDIATE_OR 7
> >> -#else
> >> -#define NUMBER_OF_LEVELS 3
> >> -#define INTERMEDIATE_OR 3
> >> -#endif
> >> -
> >> -static grub_uint64_t
> >> -get_pgtable_size (grub_uint64_t total_pages, grub_uint64_t virt_base)
> >> +static grub_err_t
> >> +get_pgtable_size (grub_uint64_t from, grub_uint64_t to, grub_uint64_t pfn)
> >> {
> >> - if (!virt_base)
> >> - total_pages++;
> >> - grub_uint64_t ret = 0;
> >> - grub_uint64_t ll = total_pages;
> >> - int i;
> >> - for (i = 0; i < NUMBER_OF_LEVELS; i++)
> >> - {
> >> - ll = (ll + POINTERS_PER_PAGE - 1) >> LOG_POINTERS_PER_PAGE;
> >> - /* PAE wants all 4 root directories present. */
> >> -#ifdef __i386__
> >> - if (i == 1)
> >> - ll = 4;
> >> -#endif
> >> - ret += ll;
> >> - }
> >> - for (i = 1; i < NUMBER_OF_LEVELS; i++)
> >> - if (virt_base >> (PAGE_SHIFT + i * LOG_POINTERS_PER_PAGE))
> >> - ret++;
> >> - return ret;
> >> -}
> >> + struct grub_xen_mapping *map, *map_cmp;
> >> + grub_uint64_t mask, bits;
> >> + int i, m;
> >>
> >> -static void
> >> -generate_page_table (grub_uint64_t *where, grub_uint64_t paging_start,
> >> - grub_uint64_t paging_end, grub_uint64_t total_pages,
> >> - grub_uint64_t virt_base, grub_xen_mfn_t *mfn_list)
> >> -{
> >> - if (!virt_base)
> >> - paging_end++;
> >> + if (n_mappings == XEN_MAX_MAPPINGS)
> >> + return grub_error (GRUB_ERR_BUG, "too many mapped areas");
> >> +
> >> + grub_dprintf ("xen", "get_pgtable_size %d from=%llx, to=%llx,
> >> pfn=%llx\n",
> >> + n_mappings, (unsigned long long) from, (unsigned long long) to,
> >> + (unsigned long long) pfn);
> >>
> >> - grub_uint64_t lx[NUMBER_OF_LEVELS], lxs[NUMBER_OF_LEVELS];
> >> - grub_uint64_t nlx, nls, sz = 0;
> >> - int l;
> >> + map = mappings + n_mappings;
> >> + grub_memset (map, 0, sizeof (*map));
> >>
> >> - nlx = paging_end;
> >> - nls = virt_base >> PAGE_SHIFT;
> >> - for (l = 0; l < NUMBER_OF_LEVELS; l++)
> >> + map->area.virt_start = from & VIRT_MASK;
> >> + map->area.virt_end = (to - 1) & VIRT_MASK;
> >> + map->area.n_pt_pages = 0;
> >> +
> >> + for (i = NUMBER_OF_LEVELS - 1; i >= 0; i--)
> >> {
> >> - nlx = (nlx + POINTERS_PER_PAGE - 1) >> LOG_POINTERS_PER_PAGE;
> >> - /* PAE wants all 4 root directories present. */
> >> + map->lvls[i].pfn_start = pfn + map->area.n_pt_pages;
> >> + if (i == NUMBER_OF_LEVELS - 1)
> >> + {
> >> + if (n_mappings == 0)
> >> + {
> >> + map->lvls[i].virt_start = 0;
> >> + map->lvls[i].virt_end = VIRT_MASK;
> >> + map->lvls[i].n_pt_pages = 1;
> >> + map->area.n_pt_pages++;
> >> + }
> >> + continue;
> >> + }
> >> +
> >> + bits = PAGE_SHIFT + (i + 1) * LOG_POINTERS_PER_PAGE;
> >> + mask = (1ULL << bits) - 1;
> >> + map->lvls[i].virt_start = map->area.virt_start & ~mask;
> >> + map->lvls[i].virt_end = map->area.virt_end | mask;
> >> #ifdef __i386__
> >> - if (l == 1)
> >> - nlx = 4;
> >> + /* PAE wants last root directory present. */
> >> + if (i == 1 && to <= 0xc0000000 && n_mappings == 0)
> >
> > Ditto.
> >
> >> + map->lvls[i].virt_end = VIRT_MASK;
> >> #endif
> >> - lx[l] = nlx;
> >> - sz += lx[l];
> >> - lxs[l] = nls & (POINTERS_PER_PAGE - 1);
> >> - if (nls && l != 0)
> >> - sz++;
> >> - nls >>= LOG_POINTERS_PER_PAGE;
> >> + for (m = 0; m < n_mappings; m++)
> >> + {
> >> + map_cmp = mappings + m;
> >> + if (map_cmp->lvls[i].virt_start == map_cmp->lvls[i].virt_end)
> >> + continue;
> >> + if (map->lvls[i].virt_start >= map_cmp->lvls[i].virt_start &&
> >> + map->lvls[i].virt_end <= map_cmp->lvls[i].virt_end)
> >> + {
> >> + map->lvls[i].virt_start = 0;
> >> + map->lvls[i].virt_end = 0;
> >> + break;
> >> + }
> >> + if (map->lvls[i].virt_start >= map_cmp->lvls[i].virt_start &&
> >> + map->lvls[i].virt_start <= map_cmp->lvls[i].virt_end)
> >> + map->lvls[i].virt_start = map_cmp->lvls[i].virt_end + 1;
> >> + if (map->lvls[i].virt_end >= map_cmp->lvls[i].virt_start &&
> >> + map->lvls[i].virt_end <= map_cmp->lvls[i].virt_end)
> >> + map->lvls[i].virt_end = map_cmp->lvls[i].virt_start - 1;
> >> + }
> >> + if (map->lvls[i].virt_start < map->lvls[i].virt_end)
> >> + map->lvls[i].n_pt_pages =
> >> + ((map->lvls[i].virt_end - map->lvls[i].virt_start) >> bits) + 1;
> >> + map->area.n_pt_pages += map->lvls[i].n_pt_pages;
> >> + grub_dprintf ("xen", "get_pgtable_size level %d: virt %llx-%llx %d
> >> pts\n",
> >> + i, (unsigned long long) map->lvls[i].virt_start,
> >> + (unsigned long long) map->lvls[i].virt_end,
> >> + (int) map->lvls[i].n_pt_pages);
> >> }
> >>
> >> - grub_uint64_t lp;
> >> - grub_uint64_t j;
> >> - grub_uint64_t *pg = (grub_uint64_t *) where;
> >> - int pr = 0;
> >> + grub_dprintf ("xen", "get_pgtable_size return: %d page tables\n",
> >> + (int) map->area.n_pt_pages);
> >> +
> >> + state.paging_start[n_mappings] = pfn;
> >> + state.paging_size[n_mappings] = map->area.n_pt_pages;
> >> +
> >> + return GRUB_ERR_NONE;
> >> +}
> >> +
> >> +static grub_uint64_t *
> >> +get_pg_table_virt (int mapping, int level)
> >> +{
> >> + grub_uint64_t pfn;
> >> + struct grub_xen_mapping *map;
> >> +
> >> + map = mappings + mapping;
> >> + pfn = map->lvls[level].pfn_start - map->lvls[NUMBER_OF_LEVELS -
> >> 1].pfn_start;
> >> + return map->where + pfn * POINTERS_PER_PAGE;
> >> +}
> >>
> >> - grub_memset (pg, 0, sz * PAGE_SIZE);
> >> +static grub_uint64_t
> >> +get_pg_table_prot (int level, grub_uint64_t pfn)
> >> +{
> >> + int m;
> >> + grub_uint64_t pfn_s, pfn_e;
> >>
> >> - lp = paging_start + lx[NUMBER_OF_LEVELS - 1];
> >> - for (l = NUMBER_OF_LEVELS - 1; l >= 1; l--)
> >> + if (level > 0)
> >> + return INTERMEDIATE_OR;
> >> + for (m = 0; m < n_mappings; m++)
> >> {
> >> - if (lxs[l] || pr)
> >> - pg[0] = page2offset (mfn_list[lp++]) | INTERMEDIATE_OR;
> >> - if (pr)
> >> - pg += POINTERS_PER_PAGE;
> >> - for (j = 0; j < lx[l - 1]; j++)
> >> - pg[j + lxs[l]] = page2offset (mfn_list[lp++]) | INTERMEDIATE_OR;
> >> - pg += lx[l] * POINTERS_PER_PAGE;
> >> - if (lxs[l])
> >> - pr = 1;
> >> + pfn_s = mappings[m].lvls[NUMBER_OF_LEVELS - 1].pfn_start;
> >> + pfn_e = mappings[m].area.n_pt_pages + pfn_s;
> >> + if (pfn >= pfn_s && pfn < pfn_e)
> >> + return 5;
> >> }
> >> + return 7;
> >
> > What 7 and 5 means?
>
> Page table protection bits.
Constants or at least comments please. Yep, I am boring. I know.
That is my style.
> > I am exhausted. Please fix above stuff and I will review this patch
> > again after fixes.
>
> I'd really like to have the maintainer's opinion on usage of constants
> vs. pure numbers. Up to now I have the impression that constants are
> used only to abstract i386 vs. x86-64. I wouldn't mind changing that,
> but I don't like modifying all my patches which are then rejected due to
> that change.
OK, let's wait for maintainer opinion. However, I feel that using
constants ease code reading. Though it does not mean that I think
that every number/string should be changed to constant. We should
find a proper balance and if plain numbers are used then there
should be at least one line comment what this number means.
> Thanks for doing the review,
You are welcome.
Daniel
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