On Sun, Feb 16, 2020 at 11:41:07AM +0100, Christophe Leroy wrote: > > > Le 16/02/2020 à 09:18, Mike Rapoport a écrit : > > From: Mike Rapoport <r...@linux.ibm.com> > > > > Implement primitives necessary for the 4th level folding, add walks of p4d > > level where appropriate and replace 5level-fixup.h with pgtable-nop4d.h. > > I don't think it is worth adding all this additionnals walks of p4d, this > patch could be limited to changes like: > > - pud = pud_offset(pgd, gpa); > + pud = pud_offset(p4d_offset(pgd, gpa), gpa); > > The additionnal walks should be added through another patch the day powerpc > need them.
Ok, I'll update the patch to reduce walking the p4d. > See below for more comments. > > > > > Signed-off-by: Mike Rapoport <r...@linux.ibm.com> > > Tested-by: Christophe Leroy <christophe.le...@c-s.fr> # 8xx and 83xx > > --- ... > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h > > b/arch/powerpc/include/asm/book3s/64/pgtable.h > > index 201a69e6a355..ddddbafff0ab 100644 > > --- a/arch/powerpc/include/asm/book3s/64/pgtable.h > > +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h > > @@ -2,7 +2,7 @@ > > #ifndef _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ > > #define _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ > > -#include <asm-generic/5level-fixup.h> > > +#include <asm-generic/pgtable-nop4d.h> > > #ifndef __ASSEMBLY__ > > #include <linux/mmdebug.h> > > @@ -251,7 +251,7 @@ extern unsigned long __pmd_frag_size_shift; > > /* Bits to mask out from a PUD to get to the PMD page */ > > #define PUD_MASKED_BITS 0xc0000000000000ffUL > > /* Bits to mask out from a PGD to get to the PUD page */ > > -#define PGD_MASKED_BITS 0xc0000000000000ffUL > > +#define P4D_MASKED_BITS 0xc0000000000000ffUL > > /* > > * Used as an indicator for rcu callback functions > > @@ -949,54 +949,60 @@ static inline bool pud_access_permitted(pud_t pud, > > bool write) > > return pte_access_permitted(pud_pte(pud), write); > > } > > -#define pgd_write(pgd) pte_write(pgd_pte(pgd)) > > +#define __p4d_raw(x) ((p4d_t) { __pgd_raw(x) }) > > +static inline __be64 p4d_raw(p4d_t x) > > +{ > > + return pgd_raw(x.pgd); > > +} > > + > > Shouldn't this be defined in asm/pgtable-be-types.h, just like other > __pxx_raw() ? Ideally yes, but this creates weird header file dependencies and untangling them would generate way too much churn. > > +#define p4d_write(p4d) pte_write(p4d_pte(p4d)) > > -static inline void pgd_clear(pgd_t *pgdp) > > +static inline void p4d_clear(p4d_t *p4dp) > > { > > - *pgdp = __pgd(0); > > + *p4dp = __p4d(0); > > } ... > > @@ -573,9 +596,15 @@ int kvmppc_create_pte(struct kvm *kvm, pgd_t *pgtable, > > pte_t pte, > > /* Traverse the guest's 2nd-level tree, allocate new levels needed */ > > pgd = pgtable + pgd_index(gpa); > > - pud = NULL; > > + p4d = NULL; > > if (pgd_present(*pgd)) > > - pud = pud_offset(pgd, gpa); > > + p4d = p4d_offset(pgd, gpa); > > + else > > + new_p4d = p4d_alloc_one(kvm->mm, gpa); > > + > > + pud = NULL; > > + if (p4d_present(*p4d)) > > + pud = pud_offset(p4d, gpa); > > Is it worth adding all this new code ? > > My understanding is that the series objective is to get rid of > __ARCH_HAS_5LEVEL_HACK, to to add support for 5 levels to an architecture > that not need it (at least for now). > If we want to add support for 5 levels, it can be done later in another > patch. > > Here I think your change could be limited to: > > - pud = pud_offset(pgd, gpa); > + pud = pud_offset(p4d_offset(pgd, gpa), gpa); This won't work. Without __ARCH_USE_5LEVEL_HACK defined pgd_present() is hardwired to 1 and the actual check for the top level is performed with p4d_present(). The 'else' clause that allocates p4d will never be taken and it could be removed, but I prefer to keep it for consistency. > > else > > new_pud = pud_alloc_one(kvm->mm, gpa); > > @@ -597,12 +626,18 @@ int kvmppc_create_pte(struct kvm *kvm, pgd_t > > *pgtable, pte_t pte, > > /* Now traverse again under the lock and change the tree */ > > ret = -ENOMEM; > > if (pgd_none(*pgd)) { > > + if (!new_p4d) > > + goto out_unlock; > > + pgd_populate(kvm->mm, pgd, new_p4d); > > + new_p4d = NULL; > > + } > > + if (p4d_none(*p4d)) { > > if (!new_pud) > > goto out_unlock; > > - pgd_populate(kvm->mm, pgd, new_pud); > > + p4d_populate(kvm->mm, p4d, new_pud); > > new_pud = NULL; > > } > > - pud = pud_offset(pgd, gpa); > > + pud = pud_offset(p4d, gpa); > > if (pud_is_leaf(*pud)) { > > unsigned long hgpa = gpa & PUD_MASK; > > @@ -1220,6 +1255,7 @@ static ssize_t debugfs_radix_read(struct file *file, > > char __user *buf, > > pgd_t *pgt; > > struct kvm_nested_guest *nested; > > pgd_t pgd, *pgdp; > > + p4d_t p4d, *p4dp; > > pud_t pud, *pudp; > > pmd_t pmd, *pmdp; > > pte_t *ptep; > > @@ -1298,7 +1334,14 @@ static ssize_t debugfs_radix_read(struct file *file, > > char __user *buf, > > continue; > > } > > - pudp = pud_offset(&pgd, gpa); > > + p4dp = p4d_offset(&pgd, gpa); > > + p4d = READ_ONCE(*p4dp); > > + if (!(p4d_val(p4d) & _PAGE_PRESENT)) { > > + gpa = (gpa & P4D_MASK) + P4D_SIZE; > > + continue; > > + } > > + > > + pudp = pud_offset(&p4d, gpa); > > Same, here you are forcing a useless read with READ_ONCE(). > > Your change could be limited to > > - pudp = pud_offset(&pgd, gpa); > + pudp = pud_offset(p4d_offset(&pgd, gpa), gpa); Here again the actual check must be done against p4d rather than pgd. We could skip READ_ONCE() for pgd, but since it is a debugfs method I don't think it is more important than code consistency. > This comment applies to many other places. I'll make another pass to see where we can take the shortcut and use pudp = pud_offset(p4d_offset(...)) > > pud = READ_ONCE(*pudp); > > if (!(pud_val(pud) & _PAGE_PRESENT)) { > > gpa = (gpa & PUD_MASK) + PUD_SIZE; > > diff --git a/arch/powerpc/lib/code-patching.c > > b/arch/powerpc/lib/code-patching.c > > index 3345f039a876..7a59f6863cec 100644 > > --- a/arch/powerpc/lib/code-patching.c > > +++ b/arch/powerpc/lib/code-patching.c > > @@ -107,13 +107,18 @@ static inline int unmap_patch_area(unsigned long addr) > > pte_t *ptep; > > pmd_t *pmdp; > > pud_t *pudp; > > + p4d_t *p4dp; > > pgd_t *pgdp; > > pgdp = pgd_offset_k(addr); > > if (unlikely(!pgdp)) > > return -EINVAL; > > - pudp = pud_offset(pgdp, addr); > > + p4dp = p4d_offset(pgdp, addr); > > + if (unlikely(!p4dp)) > > + return -EINVAL; > > + > > + pudp = pud_offset(p4dp, addr); > > if (unlikely(!pudp)) > > return -EINVAL; > > diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c > > index 0a1c65a2c565..b2fc3e71165c 100644 > > --- a/arch/powerpc/mm/book3s32/mmu.c > > +++ b/arch/powerpc/mm/book3s32/mmu.c > > @@ -312,7 +312,7 @@ void hash_preload(struct mm_struct *mm, unsigned long > > ea) > > if (!Hash) > > return; > > - pmd = pmd_offset(pud_offset(pgd_offset(mm, ea), ea), ea); > > + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, ea), ea), ea), > > ea); > > If we continue like this, in ten years this like is going to be many > kilometers long. > > I think the above would be worth a generic helper. Agree. My plan was to first unify all the architectures and then start introducing the generic helpers, like e.g. pmd_offset_mm(). > > if (!pmd_none(*pmd)) > > add_hash_page(mm->context.id, ea, pmd_val(*pmd)); > > } > > diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c > > index 2fcd321040ff..175bc33b41b7 100644 > > --- a/arch/powerpc/mm/book3s32/tlb.c > > +++ b/arch/powerpc/mm/book3s32/tlb.c > > @@ -87,7 +87,7 @@ static void flush_range(struct mm_struct *mm, unsigned > > long start, > > if (start >= end) > > return; > > end = (end - 1) | ~PAGE_MASK; > > - pmd = pmd_offset(pud_offset(pgd_offset(mm, start), start), start); > > + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, start), start), > > start), start); > > for (;;) { > > pmd_end = ((start + PGDIR_SIZE) & PGDIR_MASK) - 1; > > if (pmd_end > end) > > @@ -145,7 +145,7 @@ void flush_tlb_page(struct vm_area_struct *vma, > > unsigned long vmaddr) > > return; > > } > > mm = (vmaddr < TASK_SIZE)? vma->vm_mm: &init_mm; > > - pmd = pmd_offset(pud_offset(pgd_offset(mm, vmaddr), vmaddr), vmaddr); > > + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, vmaddr), vmaddr), > > vmaddr), vmaddr); > > if (!pmd_none(*pmd)) > > flush_hash_pages(mm->context.id, vmaddr, pmd_val(*pmd), 1); > > } > > diff --git a/arch/powerpc/mm/book3s64/hash_pgtable.c > > b/arch/powerpc/mm/book3s64/hash_pgtable.c > > index 64733b9cb20a..9cd15937e88a 100644 > > --- a/arch/powerpc/mm/book3s64/hash_pgtable.c > > +++ b/arch/powerpc/mm/book3s64/hash_pgtable.c > > @@ -148,6 +148,7 @@ void hash__vmemmap_remove_mapping(unsigned long start, > > int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t > > prot) > > { > > pgd_t *pgdp; > > + p4d_t *p4dp; > > pud_t *pudp; > > pmd_t *pmdp; > > pte_t *ptep; > > @@ -155,7 +156,8 @@ int hash__map_kernel_page(unsigned long ea, unsigned > > long pa, pgprot_t prot) > > BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE); > > if (slab_is_available()) { > > pgdp = pgd_offset_k(ea); > > - pudp = pud_alloc(&init_mm, pgdp, ea); > > + p4dp = p4d_offset(pgdp, ea); > > + pudp = pud_alloc(&init_mm, p4dp, ea); > > Could be a single line, without a new var. > > - pudp = pud_alloc(&init_mm, pgdp, ea); > + pudp = pud_alloc(&init_mm, p4d_offset(pgdp, ea), ea); > > > Same kind of comments as already done apply to the rest. > > Christophe -- Sincerely yours, Mike. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm