In x86 mm code there are multiple instances of page table walks for
different purposes.
Introduce a generic page table walker being able to cover the current
use cases. It will be used for other cases in future, too.
The page table walker needs some per-level data, so add a table for
that data. Merge it with the already existing pt_prot[] array.
Rewrite get_pgt() to use the new walker.
Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- add idx_from_va_lvl() helper (Samuel Thibault)
---
arch/x86/mm.c | 157 +++++++++++++++++++++++++++++++++++++-------------
1 file changed, 118 insertions(+), 39 deletions(-)
diff --git a/arch/x86/mm.c b/arch/x86/mm.c
index 7ddf16e4..9849b985 100644
--- a/arch/x86/mm.c
+++ b/arch/x86/mm.c
@@ -125,20 +125,30 @@ void arch_mm_preinit(void *p)
}
#endif
+static const struct {
+ unsigned int shift;
+ unsigned int entries;
+ pgentry_t prot;
+} ptdata[PAGETABLE_LEVELS + 1] = {
+ { 0, 0, 0 },
+ { L1_PAGETABLE_SHIFT, L1_PAGETABLE_ENTRIES, L1_PROT },
+ { L2_PAGETABLE_SHIFT, L2_PAGETABLE_ENTRIES, L2_PROT },
+ { L3_PAGETABLE_SHIFT, L3_PAGETABLE_ENTRIES, L3_PROT },
+#if defined(__x86_64__)
+ { L4_PAGETABLE_SHIFT, L4_PAGETABLE_ENTRIES, L4_PROT },
+#endif
+};
+
+static inline unsigned int idx_from_va_lvl(unsigned long va, unsigned int lvl)
+{
+ return (va >> ptdata[lvl].shift) & (ptdata[lvl].entries - 1);
+}
+
/*
* Make pt_pfn a new 'level' page table frame and hook it into the page
* table at offset in previous level MFN (pref_l_mfn). pt_pfn is a guest
* PFN.
*/
-static pgentry_t pt_prot[PAGETABLE_LEVELS] = {
- L1_PROT,
- L2_PROT,
- L3_PROT,
-#if defined(__x86_64__)
- L4_PROT,
-#endif
-};
-
static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
unsigned long offset, unsigned long level)
{
@@ -170,7 +180,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
mmu_updates[0].ptr = (tab[l2_table_offset(pt_page)] & PAGE_MASK) +
sizeof(pgentry_t) * l1_table_offset(pt_page);
mmu_updates[0].val = (pgentry_t)pfn_to_mfn(*pt_pfn) << PAGE_SHIFT |
- (pt_prot[level - 1] & ~_PAGE_RW);
+ (ptdata[level].prot & ~_PAGE_RW);
if ( (rc = HYPERVISOR_mmu_update(mmu_updates, 1, NULL, DOMID_SELF)) < 0 )
{
@@ -183,7 +193,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
mmu_updates[0].ptr =
((pgentry_t)prev_l_mfn << PAGE_SHIFT) + sizeof(pgentry_t) * offset;
mmu_updates[0].val = (pgentry_t)pfn_to_mfn(*pt_pfn) << PAGE_SHIFT |
- pt_prot[level];
+ ptdata[level + 1].prot;
if ( (rc = HYPERVISOR_mmu_update(mmu_updates, 1, NULL, DOMID_SELF)) < 0 )
{
@@ -192,7 +202,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
}
#else
tab = mfn_to_virt(prev_l_mfn);
- tab[offset] = (*pt_pfn << PAGE_SHIFT) | pt_prot[level];
+ tab[offset] = (*pt_pfn << PAGE_SHIFT) | ptdata[level + 1].prot;
#endif
*pt_pfn += 1;
@@ -202,6 +212,82 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
static mmu_update_t mmu_updates[L1_PAGETABLE_ENTRIES + 1];
#endif
+/*
+ * Walk recursively through all PTEs calling a specified function. The function
+ * is allowed to change the PTE, the walker will follow the new value.
+ * The walk will cover the virtual address range [from_va .. to_va].
+ * The supplied function will be called with the following parameters:
+ * va: base virtual address of the area covered by the current PTE
+ * lvl: page table level of the PTE (1 = lowest level, PAGETABLE_LEVELS =
+ * PTE in page table addressed by %cr3)
+ * is_leaf: true if PTE doesn't address another page table (it is either at
+ * level 1, or invalid, or has its PSE bit set)
+ * pte: address of the PTE
+ * par: parameter, passed to walk_pt() by caller
+ * Return value of func() being non-zero will terminate walk_pt(), walk_pt()
+ * will return that value in this case, zero else.
+ */
+static int walk_pt(unsigned long from_va, unsigned long to_va,
+ int (func)(unsigned long va, unsigned int lvl,
+ bool is_leaf, pgentry_t *pte, void *par),
+ void *par)
+{
+ unsigned int lvl = PAGETABLE_LEVELS;
+ unsigned int ptindex[PAGETABLE_LEVELS + 1];
+ unsigned long va = round_pgdown(from_va);
+ unsigned long va_lvl;
+ pgentry_t *tab[PAGETABLE_LEVELS + 1];
+ pgentry_t *pte;
+ bool is_leaf;
+ int ret;
+
+ /* Start at top level page table. */
+ tab[lvl] = pt_base;
+ ptindex[lvl] = idx_from_va_lvl(va, lvl);
+
+ while ( va < (to_va | (PAGE_SIZE - 1)) )
+ {
+ pte = tab[lvl] + ptindex[lvl];
+ is_leaf = (lvl == L1_FRAME) || (*pte & _PAGE_PSE) ||
+ !(*pte & _PAGE_PRESENT);
+ va_lvl = va & ~((1UL << ptdata[lvl].shift) - 1);
+ ret = func(va_lvl, lvl, is_leaf, pte, par);
+ if ( ret )
+ return ret;
+
+ /* PTE might have been modified by func(), reevaluate leaf state. */
+ is_leaf = (lvl == L1_FRAME) || (*pte & _PAGE_PSE) ||
+ !(*pte & _PAGE_PRESENT);
+
+ if ( is_leaf )
+ {
+ /* Reached a leaf PTE. Advance to next page. */
+ va += 1UL << ptdata[lvl].shift;
+ ptindex[lvl]++;
+
+ /* Check for the need to traverse up again. */
+ while ( ptindex[lvl] == ptdata[lvl].entries )
+ {
+ /* End of virtual address space? */
+ if ( lvl == PAGETABLE_LEVELS )
+ return 0;
+ /* Reached end of current page table, one level up. */
+ lvl++;
+ ptindex[lvl]++;
+ }
+ }
+ else
+ {
+ /* Not a leaf, walk one level down. */
+ lvl--;
+ tab[lvl] = mfn_to_virt(pte_to_mfn(*pte));
+ ptindex[lvl] = idx_from_va_lvl(va, lvl);
+ }
+ }
+
+ return 0;
+}
+
/*
* Build the initial pagetable.
*/
@@ -407,36 +493,29 @@ static void set_readonly(void *text, void *etext)
/*
* get the PTE for virtual address va if it exists. Otherwise NULL.
*/
-static pgentry_t *get_pgt(unsigned long va)
+static int get_pgt_func(unsigned long va, unsigned int lvl, bool is_leaf,
+ pgentry_t *pte, void *par)
{
- unsigned long mfn;
- pgentry_t *tab;
- unsigned offset;
+ pgentry_t **result;
- tab = pt_base;
- mfn = virt_to_mfn(pt_base);
+ if ( !(*pte & _PAGE_PRESENT) && lvl > L1_FRAME )
+ return -1;
-#if defined(__x86_64__)
- offset = l4_table_offset(va);
- if ( !(tab[offset] & _PAGE_PRESENT) )
- return NULL;
- mfn = pte_to_mfn(tab[offset]);
- tab = mfn_to_virt(mfn);
-#endif
- offset = l3_table_offset(va);
- if ( !(tab[offset] & _PAGE_PRESENT) )
- return NULL;
- mfn = pte_to_mfn(tab[offset]);
- tab = mfn_to_virt(mfn);
- offset = l2_table_offset(va);
- if ( !(tab[offset] & _PAGE_PRESENT) )
- return NULL;
- if ( tab[offset] & _PAGE_PSE )
- return &tab[offset];
- mfn = pte_to_mfn(tab[offset]);
- tab = mfn_to_virt(mfn);
- offset = l1_table_offset(va);
- return &tab[offset];
+ if ( lvl > L1_FRAME && !(*pte & _PAGE_PSE) )
+ return 0;
+
+ result = par;
+ *result = pte;
+
+ return 0;
+}
+
+static pgentry_t *get_pgt(unsigned long va)
+{
+ pgentry_t *tab = NULL;
+
+ walk_pt(va, va, get_pgt_func, &tab);
+ return tab;
}
--
2.43.0Juergen Gross, le mar. 13 août 2024 15:41:56 +0200, a ecrit:
> In x86 mm code there are multiple instances of page table walks for
> different purposes.
>
> Introduce a generic page table walker being able to cover the current
> use cases. It will be used for other cases in future, too.
>
> The page table walker needs some per-level data, so add a table for
> that data. Merge it with the already existing pt_prot[] array.
>
> Rewrite get_pgt() to use the new walker.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: SAmuel Thibault <samuel.thibault@ens-lyon.org>
> ---
> V2:
> - add idx_from_va_lvl() helper (Samuel Thibault)
> ---
> arch/x86/mm.c | 157 +++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 118 insertions(+), 39 deletions(-)
>
> diff --git a/arch/x86/mm.c b/arch/x86/mm.c
> index 7ddf16e4..9849b985 100644
> --- a/arch/x86/mm.c
> +++ b/arch/x86/mm.c
> @@ -125,20 +125,30 @@ void arch_mm_preinit(void *p)
> }
> #endif
>
> +static const struct {
> + unsigned int shift;
> + unsigned int entries;
> + pgentry_t prot;
> +} ptdata[PAGETABLE_LEVELS + 1] = {
> + { 0, 0, 0 },
> + { L1_PAGETABLE_SHIFT, L1_PAGETABLE_ENTRIES, L1_PROT },
> + { L2_PAGETABLE_SHIFT, L2_PAGETABLE_ENTRIES, L2_PROT },
> + { L3_PAGETABLE_SHIFT, L3_PAGETABLE_ENTRIES, L3_PROT },
> +#if defined(__x86_64__)
> + { L4_PAGETABLE_SHIFT, L4_PAGETABLE_ENTRIES, L4_PROT },
> +#endif
> +};
> +
> +static inline unsigned int idx_from_va_lvl(unsigned long va, unsigned int lvl)
> +{
> + return (va >> ptdata[lvl].shift) & (ptdata[lvl].entries - 1);
> +}
> +
> /*
> * Make pt_pfn a new 'level' page table frame and hook it into the page
> * table at offset in previous level MFN (pref_l_mfn). pt_pfn is a guest
> * PFN.
> */
> -static pgentry_t pt_prot[PAGETABLE_LEVELS] = {
> - L1_PROT,
> - L2_PROT,
> - L3_PROT,
> -#if defined(__x86_64__)
> - L4_PROT,
> -#endif
> -};
> -
> static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
> unsigned long offset, unsigned long level)
> {
> @@ -170,7 +180,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
> mmu_updates[0].ptr = (tab[l2_table_offset(pt_page)] & PAGE_MASK) +
> sizeof(pgentry_t) * l1_table_offset(pt_page);
> mmu_updates[0].val = (pgentry_t)pfn_to_mfn(*pt_pfn) << PAGE_SHIFT |
> - (pt_prot[level - 1] & ~_PAGE_RW);
> + (ptdata[level].prot & ~_PAGE_RW);
>
> if ( (rc = HYPERVISOR_mmu_update(mmu_updates, 1, NULL, DOMID_SELF)) < 0 )
> {
> @@ -183,7 +193,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
> mmu_updates[0].ptr =
> ((pgentry_t)prev_l_mfn << PAGE_SHIFT) + sizeof(pgentry_t) * offset;
> mmu_updates[0].val = (pgentry_t)pfn_to_mfn(*pt_pfn) << PAGE_SHIFT |
> - pt_prot[level];
> + ptdata[level + 1].prot;
>
> if ( (rc = HYPERVISOR_mmu_update(mmu_updates, 1, NULL, DOMID_SELF)) < 0 )
> {
> @@ -192,7 +202,7 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
> }
> #else
> tab = mfn_to_virt(prev_l_mfn);
> - tab[offset] = (*pt_pfn << PAGE_SHIFT) | pt_prot[level];
> + tab[offset] = (*pt_pfn << PAGE_SHIFT) | ptdata[level + 1].prot;
> #endif
>
> *pt_pfn += 1;
> @@ -202,6 +212,82 @@ static void new_pt_frame(unsigned long *pt_pfn, unsigned long prev_l_mfn,
> static mmu_update_t mmu_updates[L1_PAGETABLE_ENTRIES + 1];
> #endif
>
> +/*
> + * Walk recursively through all PTEs calling a specified function. The function
> + * is allowed to change the PTE, the walker will follow the new value.
> + * The walk will cover the virtual address range [from_va .. to_va].
> + * The supplied function will be called with the following parameters:
> + * va: base virtual address of the area covered by the current PTE
> + * lvl: page table level of the PTE (1 = lowest level, PAGETABLE_LEVELS =
> + * PTE in page table addressed by %cr3)
> + * is_leaf: true if PTE doesn't address another page table (it is either at
> + * level 1, or invalid, or has its PSE bit set)
> + * pte: address of the PTE
> + * par: parameter, passed to walk_pt() by caller
> + * Return value of func() being non-zero will terminate walk_pt(), walk_pt()
> + * will return that value in this case, zero else.
> + */
> +static int walk_pt(unsigned long from_va, unsigned long to_va,
> + int (func)(unsigned long va, unsigned int lvl,
> + bool is_leaf, pgentry_t *pte, void *par),
> + void *par)
> +{
> + unsigned int lvl = PAGETABLE_LEVELS;
> + unsigned int ptindex[PAGETABLE_LEVELS + 1];
> + unsigned long va = round_pgdown(from_va);
> + unsigned long va_lvl;
> + pgentry_t *tab[PAGETABLE_LEVELS + 1];
> + pgentry_t *pte;
> + bool is_leaf;
> + int ret;
> +
> + /* Start at top level page table. */
> + tab[lvl] = pt_base;
> + ptindex[lvl] = idx_from_va_lvl(va, lvl);
> +
> + while ( va < (to_va | (PAGE_SIZE - 1)) )
> + {
> + pte = tab[lvl] + ptindex[lvl];
> + is_leaf = (lvl == L1_FRAME) || (*pte & _PAGE_PSE) ||
> + !(*pte & _PAGE_PRESENT);
> + va_lvl = va & ~((1UL << ptdata[lvl].shift) - 1);
> + ret = func(va_lvl, lvl, is_leaf, pte, par);
> + if ( ret )
> + return ret;
> +
> + /* PTE might have been modified by func(), reevaluate leaf state. */
> + is_leaf = (lvl == L1_FRAME) || (*pte & _PAGE_PSE) ||
> + !(*pte & _PAGE_PRESENT);
> +
> + if ( is_leaf )
> + {
> + /* Reached a leaf PTE. Advance to next page. */
> + va += 1UL << ptdata[lvl].shift;
> + ptindex[lvl]++;
> +
> + /* Check for the need to traverse up again. */
> + while ( ptindex[lvl] == ptdata[lvl].entries )
> + {
> + /* End of virtual address space? */
> + if ( lvl == PAGETABLE_LEVELS )
> + return 0;
> + /* Reached end of current page table, one level up. */
> + lvl++;
> + ptindex[lvl]++;
> + }
> + }
> + else
> + {
> + /* Not a leaf, walk one level down. */
> + lvl--;
> + tab[lvl] = mfn_to_virt(pte_to_mfn(*pte));
> + ptindex[lvl] = idx_from_va_lvl(va, lvl);
> + }
> + }
> +
> + return 0;
> +}
> +
> /*
> * Build the initial pagetable.
> */
> @@ -407,36 +493,29 @@ static void set_readonly(void *text, void *etext)
> /*
> * get the PTE for virtual address va if it exists. Otherwise NULL.
> */
> -static pgentry_t *get_pgt(unsigned long va)
> +static int get_pgt_func(unsigned long va, unsigned int lvl, bool is_leaf,
> + pgentry_t *pte, void *par)
> {
> - unsigned long mfn;
> - pgentry_t *tab;
> - unsigned offset;
> + pgentry_t **result;
>
> - tab = pt_base;
> - mfn = virt_to_mfn(pt_base);
> + if ( !(*pte & _PAGE_PRESENT) && lvl > L1_FRAME )
> + return -1;
>
> -#if defined(__x86_64__)
> - offset = l4_table_offset(va);
> - if ( !(tab[offset] & _PAGE_PRESENT) )
> - return NULL;
> - mfn = pte_to_mfn(tab[offset]);
> - tab = mfn_to_virt(mfn);
> -#endif
> - offset = l3_table_offset(va);
> - if ( !(tab[offset] & _PAGE_PRESENT) )
> - return NULL;
> - mfn = pte_to_mfn(tab[offset]);
> - tab = mfn_to_virt(mfn);
> - offset = l2_table_offset(va);
> - if ( !(tab[offset] & _PAGE_PRESENT) )
> - return NULL;
> - if ( tab[offset] & _PAGE_PSE )
> - return &tab[offset];
> - mfn = pte_to_mfn(tab[offset]);
> - tab = mfn_to_virt(mfn);
> - offset = l1_table_offset(va);
> - return &tab[offset];
> + if ( lvl > L1_FRAME && !(*pte & _PAGE_PSE) )
> + return 0;
> +
> + result = par;
> + *result = pte;
> +
> + return 0;
> +}
> +
> +static pgentry_t *get_pgt(unsigned long va)
> +{
> + pgentry_t *tab = NULL;
> +
> + walk_pt(va, va, get_pgt_func, &tab);
> + return tab;
> }
>
>
> --
> 2.43.0
>
--
Samuel
<N> je déteste import
<N> parce que lorsque tu fais du python et que tu oublies le #!/bin/env python et que tu mets le fichier exécutable
<N> import est exécuté
-+- #ens-mim - pourquoi mon script python change le curseur de la souris ?! -+-
On 20.08.2024 13:52, Samuel Thibault wrote: > Juergen Gross, le mar. 13 août 2024 15:41:56 +0200, a ecrit: >> In x86 mm code there are multiple instances of page table walks for >> different purposes. >> >> Introduce a generic page table walker being able to cover the current >> use cases. It will be used for other cases in future, too. >> >> The page table walker needs some per-level data, so add a table for >> that data. Merge it with the already existing pt_prot[] array. >> >> Rewrite get_pgt() to use the new walker. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> > > Reviewed-by: SAmuel Thibault <samuel.thibault@ens-lyon.org> Samuel - I've taken the liberty to convert the odd upper-case A. Jürgen - looking at the mini-os short-log is quite odd, and increasingly so. In the mini-os repo surely all commits are about mini-os; the subject prefixes are kind of pointless. To nevertheless identify such patches on xen-devel@, may I suggest to use (taking this patch as an example) "[PATCH MINI-OS] mm: introduce generic page table walk function" instead (or, of course, whatever variation thereof you may like better)? Jan
Jan Beulich, le mar. 20 août 2024 16:17:26 +0200, a ecrit: > On 20.08.2024 13:52, Samuel Thibault wrote: > > Juergen Gross, le mar. 13 août 2024 15:41:56 +0200, a ecrit: > >> In x86 mm code there are multiple instances of page table walks for > >> different purposes. > >> > >> Introduce a generic page table walker being able to cover the current > >> use cases. It will be used for other cases in future, too. > >> > >> The page table walker needs some per-level data, so add a table for > >> that data. Merge it with the already existing pt_prot[] array. > >> > >> Rewrite get_pgt() to use the new walker. > >> > >> Signed-off-by: Juergen Gross <jgross@suse.com> > > > > Reviewed-by: SAmuel Thibault <samuel.thibault@ens-lyon.org> > > Samuel - I've taken the liberty to convert the odd upper-case A. Oh, sure, thanks :) Samuel
On 20.08.24 16:17, Jan Beulich wrote: > On 20.08.2024 13:52, Samuel Thibault wrote: >> Juergen Gross, le mar. 13 août 2024 15:41:56 +0200, a ecrit: >>> In x86 mm code there are multiple instances of page table walks for >>> different purposes. >>> >>> Introduce a generic page table walker being able to cover the current >>> use cases. It will be used for other cases in future, too. >>> >>> The page table walker needs some per-level data, so add a table for >>> that data. Merge it with the already existing pt_prot[] array. >>> >>> Rewrite get_pgt() to use the new walker. >>> >>> Signed-off-by: Juergen Gross <jgross@suse.com> >> >> Reviewed-by: SAmuel Thibault <samuel.thibault@ens-lyon.org> > > Samuel - I've taken the liberty to convert the odd upper-case A. > > Jürgen - looking at the mini-os short-log is quite odd, and increasingly > so. In the mini-os repo surely all commits are about mini-os; the > subject prefixes are kind of pointless. To nevertheless identify such > patches on xen-devel@, may I suggest to use (taking this patch as an > example) "[PATCH MINI-OS] mm: introduce generic page table walk function" > instead (or, of course, whatever variation thereof you may like better)? Okay, fine with me. Juergen
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