Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time
From: Kirill A. Shutemov
Date: Tue Jul 25 2017 - 05:06:41 EST
On Tue, Jul 18, 2017 at 04:24:06PM +0200, Juergen Gross wrote:
> Xen PV guests will never run with 5-level-paging enabled. So I guess you
> can drop the complete if (IS_ENABLED(CONFIG_X86_5LEVEL)) {} block.
There is more code to drop from mmu_pv.c.
But while there, I thought if with boot-time 5-level paging switching we
can allow kernel to compile with XEN_PV and XEN_PVH, so the kernel image
can be used in these XEN modes with 4-level paging.
Could you check if with the patch below we can boot in XEN_PV and XEN_PVH
modes?
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 7ebb56e99389..6d67d3530698 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -37,12 +37,12 @@
*
*/
+#define l4_index(x) (((x) >> P4D_SHIFT) & 511)
#define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
-#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
-PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE48)
-PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
-#endif
+L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE48)
+L4_START_KERNEL = l4_index(__START_KERNEL_map)
+
L3_START_KERNEL = pud_index(__START_KERNEL_map)
.text
@@ -347,9 +347,9 @@ NEXT_PAGE(early_dynamic_pgts)
#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
NEXT_PAGE(init_top_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .org init_top_pgt + PGD_PAGE_OFFSET*8, 0
+ .org init_top_pgt + L4_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .org init_top_pgt + PGD_START_KERNEL*8, 0
+ .org init_top_pgt + L4_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 1ecd419811a2..027987638e98 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -17,9 +17,6 @@ config XEN_PV
bool "Xen PV guest support"
default y
depends on XEN
- # XEN_PV is not ready to work with 5-level paging.
- # Changes to hypervisor are also required.
- depends on !X86_5LEVEL
select XEN_HAVE_PVMMU
select XEN_HAVE_VPMU
help
@@ -78,6 +75,4 @@ config XEN_DEBUG_FS
config XEN_PVH
bool "Support for running as a PVH guest"
depends on XEN && XEN_PVHVM && ACPI
- # Pre-built page tables are not ready to handle 5-level paging.
- depends on !X86_5LEVEL
def_bool n
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index b0530184c637..3116649302f2 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -469,7 +469,7 @@ __visible pmd_t xen_make_pmd(pmdval_t pmd)
}
PV_CALLEE_SAVE_REGS_THUNK(xen_make_pmd);
-#if CONFIG_PGTABLE_LEVELS == 4
+#ifdef CONFIG_X86_64
__visible pudval_t xen_pud_val(pud_t pud)
{
return pte_mfn_to_pfn(pud.pud);
@@ -558,7 +558,7 @@ static void xen_set_p4d(p4d_t *ptr, p4d_t val)
xen_mc_issue(PARAVIRT_LAZY_MMU);
}
-#endif /* CONFIG_PGTABLE_LEVELS == 4 */
+#endif /* CONFIG_X86_64 */
static int xen_pmd_walk(struct mm_struct *mm, pmd_t *pmd,
int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
@@ -600,21 +600,17 @@ static int xen_p4d_walk(struct mm_struct *mm, p4d_t *p4d,
int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
bool last, unsigned long limit)
{
- int i, nr, flush = 0;
+ int flush = 0;
+ pud_t *pud;
- nr = last ? p4d_index(limit) + 1 : PTRS_PER_P4D;
- for (i = 0; i < nr; i++) {
- pud_t *pud;
- if (p4d_none(p4d[i]))
- continue;
+ if (p4d_none(*p4d))
+ return flush;
- pud = pud_offset(&p4d[i], 0);
- if (PTRS_PER_PUD > 1)
- flush |= (*func)(mm, virt_to_page(pud), PT_PUD);
- flush |= xen_pud_walk(mm, pud, func,
- last && i == nr - 1, limit);
- }
+ pud = pud_offset(p4d, 0);
+ if (PTRS_PER_PUD > 1)
+ flush |= (*func)(mm, virt_to_page(pud), PT_PUD);
+ flush |= xen_pud_walk(mm, pud, func, last, limit);
return flush;
}
@@ -664,8 +660,6 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t *pgd,
continue;
p4d = p4d_offset(&pgd[i], 0);
- if (PTRS_PER_P4D > 1)
- flush |= (*func)(mm, virt_to_page(p4d), PT_P4D);
flush |= xen_p4d_walk(mm, p4d, func, i == nr - 1, limit);
}
@@ -1197,22 +1191,14 @@ static void __init xen_cleanmfnmap(unsigned long vaddr)
{
pgd_t *pgd;
p4d_t *p4d;
- unsigned int i;
bool unpin;
unpin = (vaddr == 2 * PGDIR_SIZE);
vaddr &= PMD_MASK;
pgd = pgd_offset_k(vaddr);
p4d = p4d_offset(pgd, 0);
- for (i = 0; i < PTRS_PER_P4D; i++) {
- if (p4d_none(p4d[i]))
- continue;
- xen_cleanmfnmap_p4d(p4d + i, unpin);
- }
- if (!p4d_folded) {
- set_pgd(pgd, __pgd(0));
- xen_cleanmfnmap_free_pgtbl(p4d, unpin);
- }
+ if (!p4d_none(*p4d))
+ xen_cleanmfnmap_p4d(p4d, unpin);
}
static void __init xen_pagetable_p2m_free(void)
@@ -1718,7 +1704,7 @@ static void xen_release_pmd(unsigned long pfn)
xen_release_ptpage(pfn, PT_PMD);
}
-#if CONFIG_PGTABLE_LEVELS >= 4
+#ifdef CONFIG_X86_64
static void xen_alloc_pud(struct mm_struct *mm, unsigned long pfn)
{
xen_alloc_ptpage(mm, pfn, PT_PUD);
@@ -2055,13 +2041,12 @@ static phys_addr_t __init xen_early_virt_to_phys(unsigned long vaddr)
*/
void __init xen_relocate_p2m(void)
{
- phys_addr_t size, new_area, pt_phys, pmd_phys, pud_phys, p4d_phys;
+ phys_addr_t size, new_area, pt_phys, pmd_phys, pud_phys;
unsigned long p2m_pfn, p2m_pfn_end, n_frames, pfn, pfn_end;
- int n_pte, n_pt, n_pmd, n_pud, n_p4d, idx_pte, idx_pt, idx_pmd, idx_pud, idx_p4d;
+ int n_pte, n_pt, n_pmd, n_pud, idx_pte, idx_pt, idx_pmd, idx_pud;
pte_t *pt;
pmd_t *pmd;
pud_t *pud;
- p4d_t *p4d = NULL;
pgd_t *pgd;
unsigned long *new_p2m;
int save_pud;
@@ -2071,11 +2056,7 @@ void __init xen_relocate_p2m(void)
n_pt = roundup(size, PMD_SIZE) >> PMD_SHIFT;
n_pmd = roundup(size, PUD_SIZE) >> PUD_SHIFT;
n_pud = roundup(size, P4D_SIZE) >> P4D_SHIFT;
- if (PTRS_PER_P4D > 1)
- n_p4d = roundup(size, PGDIR_SIZE) >> PGDIR_SHIFT;
- else
- n_p4d = 0;
- n_frames = n_pte + n_pt + n_pmd + n_pud + n_p4d;
+ n_frames = n_pte + n_pt + n_pmd + n_pud;
new_area = xen_find_free_area(PFN_PHYS(n_frames));
if (!new_area) {
@@ -2091,76 +2072,56 @@ void __init xen_relocate_p2m(void)
* To avoid any possible virtual address collision, just use
* 2 * PUD_SIZE for the new area.
*/
- p4d_phys = new_area;
- pud_phys = p4d_phys + PFN_PHYS(n_p4d);
+ pud_phys = new_area;
pmd_phys = pud_phys + PFN_PHYS(n_pud);
pt_phys = pmd_phys + PFN_PHYS(n_pmd);
p2m_pfn = PFN_DOWN(pt_phys) + n_pt;
pgd = __va(read_cr3_pa());
new_p2m = (unsigned long *)(2 * PGDIR_SIZE);
- idx_p4d = 0;
save_pud = n_pud;
- do {
- if (n_p4d > 0) {
- p4d = early_memremap(p4d_phys, PAGE_SIZE);
- clear_page(p4d);
- n_pud = min(save_pud, PTRS_PER_P4D);
- }
- for (idx_pud = 0; idx_pud < n_pud; idx_pud++) {
- pud = early_memremap(pud_phys, PAGE_SIZE);
- clear_page(pud);
- for (idx_pmd = 0; idx_pmd < min(n_pmd, PTRS_PER_PUD);
- idx_pmd++) {
- pmd = early_memremap(pmd_phys, PAGE_SIZE);
- clear_page(pmd);
- for (idx_pt = 0; idx_pt < min(n_pt, PTRS_PER_PMD);
- idx_pt++) {
- pt = early_memremap(pt_phys, PAGE_SIZE);
- clear_page(pt);
- for (idx_pte = 0;
- idx_pte < min(n_pte, PTRS_PER_PTE);
- idx_pte++) {
- set_pte(pt + idx_pte,
- pfn_pte(p2m_pfn, PAGE_KERNEL));
- p2m_pfn++;
- }
- n_pte -= PTRS_PER_PTE;
- early_memunmap(pt, PAGE_SIZE);
- make_lowmem_page_readonly(__va(pt_phys));
- pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE,
- PFN_DOWN(pt_phys));
- set_pmd(pmd + idx_pt,
- __pmd(_PAGE_TABLE | pt_phys));
- pt_phys += PAGE_SIZE;
+ for (idx_pud = 0; idx_pud < n_pud; idx_pud++) {
+ pud = early_memremap(pud_phys, PAGE_SIZE);
+ clear_page(pud);
+ for (idx_pmd = 0; idx_pmd < min(n_pmd, PTRS_PER_PUD);
+ idx_pmd++) {
+ pmd = early_memremap(pmd_phys, PAGE_SIZE);
+ clear_page(pmd);
+ for (idx_pt = 0; idx_pt < min(n_pt, PTRS_PER_PMD);
+ idx_pt++) {
+ pt = early_memremap(pt_phys, PAGE_SIZE);
+ clear_page(pt);
+ for (idx_pte = 0;
+ idx_pte < min(n_pte, PTRS_PER_PTE);
+ idx_pte++) {
+ set_pte(pt + idx_pte,
+ pfn_pte(p2m_pfn, PAGE_KERNEL));
+ p2m_pfn++;
}
- n_pt -= PTRS_PER_PMD;
- early_memunmap(pmd, PAGE_SIZE);
- make_lowmem_page_readonly(__va(pmd_phys));
- pin_pagetable_pfn(MMUEXT_PIN_L2_TABLE,
- PFN_DOWN(pmd_phys));
- set_pud(pud + idx_pmd, __pud(_PAGE_TABLE | pmd_phys));
- pmd_phys += PAGE_SIZE;
+ n_pte -= PTRS_PER_PTE;
+ early_memunmap(pt, PAGE_SIZE);
+ make_lowmem_page_readonly(__va(pt_phys));
+ pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE,
+ PFN_DOWN(pt_phys));
+ set_pmd(pmd + idx_pt,
+ __pmd(_PAGE_TABLE | pt_phys));
+ pt_phys += PAGE_SIZE;
}
- n_pmd -= PTRS_PER_PUD;
- early_memunmap(pud, PAGE_SIZE);
- make_lowmem_page_readonly(__va(pud_phys));
- pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(pud_phys));
- if (n_p4d > 0)
- set_p4d(p4d + idx_pud, __p4d(_PAGE_TABLE | pud_phys));
- else
- set_pgd(pgd + 2 + idx_pud, __pgd(_PAGE_TABLE | pud_phys));
- pud_phys += PAGE_SIZE;
- }
- if (n_p4d > 0) {
- save_pud -= PTRS_PER_P4D;
- early_memunmap(p4d, PAGE_SIZE);
- make_lowmem_page_readonly(__va(p4d_phys));
- pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, PFN_DOWN(p4d_phys));
- set_pgd(pgd + 2 + idx_p4d, __pgd(_PAGE_TABLE | p4d_phys));
- p4d_phys += PAGE_SIZE;
+ n_pt -= PTRS_PER_PMD;
+ early_memunmap(pmd, PAGE_SIZE);
+ make_lowmem_page_readonly(__va(pmd_phys));
+ pin_pagetable_pfn(MMUEXT_PIN_L2_TABLE,
+ PFN_DOWN(pmd_phys));
+ set_pud(pud + idx_pmd, __pud(_PAGE_TABLE | pmd_phys));
+ pmd_phys += PAGE_SIZE;
}
- } while (++idx_p4d < n_p4d);
+ n_pmd -= PTRS_PER_PUD;
+ early_memunmap(pud, PAGE_SIZE);
+ make_lowmem_page_readonly(__va(pud_phys));
+ pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(pud_phys));
+ set_pgd(pgd + 2 + idx_pud, __pgd(_PAGE_TABLE | pud_phys));
+ pud_phys += PAGE_SIZE;
+ }
/* Now copy the old p2m info to the new area. */
memcpy(new_p2m, xen_p2m_addr, size);
@@ -2387,7 +2348,7 @@ static void __init xen_post_allocator_init(void)
pv_mmu_ops.set_pte = xen_set_pte;
pv_mmu_ops.set_pmd = xen_set_pmd;
pv_mmu_ops.set_pud = xen_set_pud;
-#if CONFIG_PGTABLE_LEVELS >= 4
+#ifdef CONFIG_X86_64
pv_mmu_ops.set_p4d = xen_set_p4d;
#endif
@@ -2397,7 +2358,7 @@ static void __init xen_post_allocator_init(void)
pv_mmu_ops.alloc_pmd = xen_alloc_pmd;
pv_mmu_ops.release_pte = xen_release_pte;
pv_mmu_ops.release_pmd = xen_release_pmd;
-#if CONFIG_PGTABLE_LEVELS >= 4
+#ifdef CONFIG_X86_64
pv_mmu_ops.alloc_pud = xen_alloc_pud;
pv_mmu_ops.release_pud = xen_release_pud;
#endif
@@ -2463,14 +2424,14 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
.make_pmd = PV_CALLEE_SAVE(xen_make_pmd),
.pmd_val = PV_CALLEE_SAVE(xen_pmd_val),
-#if CONFIG_PGTABLE_LEVELS >= 4
+#ifdef CONFIG_X86_64
.pud_val = PV_CALLEE_SAVE(xen_pud_val),
.make_pud = PV_CALLEE_SAVE(xen_make_pud),
.set_p4d = xen_set_p4d_hyper,
.alloc_pud = xen_alloc_pmd_init,
.release_pud = xen_release_pmd_init,
-#endif /* CONFIG_PGTABLE_LEVELS == 4 */
+#endif /* CONFIG_X86_64 */
.activate_mm = xen_activate_mm,
.dup_mmap = xen_dup_mmap,
--
Kirill A. Shutemov