On Wed, May 28, 2014 at 01:04:50PM +0100, Marc Zyngier wrote:
> On 26/05/14 16:20, Christoffer Dall wrote:
> > unmap_range() was utterly broken, to quote Marc, and broke in all sorts
> > of situations. It was also quite complicated to follow and didn't
> > follow the usual scheme of having a separate iterating function for each
> > level of page tables.
> >
> > Address this by refactoring the code and introduce a pgd_clear()
> > function.
> >
> > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> > ---
> > arch/arm/include/asm/kvm_mmu.h | 12 ++++
> > arch/arm/kvm/mmu.c | 126 ++++++++++++++++++++++-----------------
> > arch/arm64/include/asm/kvm_mmu.h | 15 +++++
> > 3 files changed, 99 insertions(+), 54 deletions(-)
> >
> > diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> > index 5c7aa3c..5cc0b0f 100644
> > --- a/arch/arm/include/asm/kvm_mmu.h
> > +++ b/arch/arm/include/asm/kvm_mmu.h
> > @@ -127,6 +127,18 @@ static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
> > (__boundary - 1 < (end) - 1)? __boundary: (end); \
> > })
> >
> > +static inline bool kvm_page_empty(void *ptr)
> > +{
> > + struct page *ptr_page = virt_to_page(ptr);
> > + return page_count(ptr_page) == 1;
> > +}
> > +
> > +
> > +#define kvm_pte_table_empty(ptep) kvm_page_empty(ptep)
> > +#define kvm_pmd_table_empty(pmdp) kvm_page_empty(pmdp)
> > +#define kvm_pud_table_empty(pudp) (0)
> > +
> > +
> > struct kvm;
> >
> > #define kvm_flush_dcache_to_poc(a,l) __cpuc_flush_dcache_area((a), (l))
> > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> > index 16f8049..0572522 100644
> > --- a/arch/arm/kvm/mmu.c
> > +++ b/arch/arm/kvm/mmu.c
> > @@ -46,6 +46,10 @@ static phys_addr_t hyp_idmap_vector;
> >
> > #define kvm_pmd_huge(_x) (pmd_huge(_x) || pmd_trans_huge(_x))
> >
> > +#ifndef __unused
> > +# define __unused __attribute__((unused))
> > +#endif
> > +
>
> Do we actually need this?
>
my GCC complains in clear_pgd_entry if pud's are not used. Other
suggestions on how to solve this are very welcome.
> > static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
> > {
> > /*
> > @@ -90,10 +94,13 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
> > return p;
> > }
> >
> > -static bool page_empty(void *ptr)
> > +static void clear_pgd_entry(struct kvm *kvm, pgd_t *pgd, phys_addr_t addr)
> > {
> > - struct page *ptr_page = virt_to_page(ptr);
> > - return page_count(ptr_page) == 1;
> > + pud_t *pud_table __unused = pud_offset(pgd, 0);
> > + pgd_clear(pgd);
> > + kvm_tlb_flush_vmid_ipa(kvm, addr);
> > + pud_free(NULL, pud_table);
> > + put_page(virt_to_page(pgd));
> > }
> >
> > static void clear_pud_entry(struct kvm *kvm, pud_t *pud, phys_addr_t addr)
> > @@ -124,70 +131,81 @@ static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
> > put_page(virt_to_page(pmd));
> > }
> >
> > -static void clear_pte_entry(struct kvm *kvm, pte_t *pte, phys_addr_t addr)
> > +static void unmap_ptes(struct kvm *kvm, pmd_t *pmd,
> > + unsigned long long addr, unsigned long long end)
> > {
> > - if (pte_present(*pte)) {
> > - kvm_set_pte(pte, __pte(0));
> > - put_page(virt_to_page(pte));
> > - kvm_tlb_flush_vmid_ipa(kvm, addr);
> > - }
> > + pte_t *pte, *start_pte;
> > + unsigned long long start_addr = addr;
> > +
> > + start_pte = pte = pte_offset_kernel(pmd, addr);
> > + do {
> > + if (!pte_none(*pte)) {
> > + kvm_set_pte(pte, __pte(0));
> > + put_page(virt_to_page(pte));
> > + kvm_tlb_flush_vmid_ipa(kvm, addr);
> > + }
> > + } while (pte++, addr += PAGE_SIZE, addr != end);
> > +
> > + if (kvm_pte_table_empty(start_pte))
> > + clear_pmd_entry(kvm, pmd, start_addr);
> > }
> >
> > -static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
> > - unsigned long long start, u64 size)
> > +static void unmap_pmds(struct kvm *kvm, pud_t *pud,
> > + unsigned long long addr, unsigned long long end)
> > {
> > - pgd_t *pgd;
> > - pud_t *pud;
> > - pmd_t *pmd;
> > - pte_t *pte;
> > - unsigned long long addr = start, end = start + size;
> > - u64 next;
> > -
> > - while (addr < end) {
> > - pgd = pgdp + pgd_index(addr);
> > - pud = pud_offset(pgd, addr);
> > - pte = NULL;
> > - if (pud_none(*pud)) {
> > - addr = kvm_pud_addr_end(addr, end);
> > - continue;
> > - }
> > + unsigned long long next, start_addr = addr;
> > + pmd_t *pmd, *start_pmd;
> >
> > - if (pud_huge(*pud)) {
> > - /*
> > - * If we are dealing with a huge pud, just clear it and
> > - * move on.
> > - */
> > - clear_pud_entry(kvm, pud, addr);
> > - addr = kvm_pud_addr_end(addr, end);
> > - continue;
> > + start_pmd = pmd = pmd_offset(pud, addr);
> > + do {
> > + next = kvm_pmd_addr_end(addr, end);
> > + if (!pmd_none(*pmd)) {
> > + if (kvm_pmd_huge(*pmd))
> > + clear_pmd_entry(kvm, pmd, addr);
> > + else
> > + unmap_ptes(kvm, pmd, addr, next);
> > }
> > + } while (pmd++, addr = next, addr != end);
> >
> > - pmd = pmd_offset(pud, addr);
> > - if (pmd_none(*pmd)) {
> > - addr = kvm_pmd_addr_end(addr, end);
> > - continue;
> > - }
> > + if (kvm_pmd_table_empty(start_pmd))
> > + clear_pud_entry(kvm, pud, start_addr);
> > +}
> >
> > - if (!kvm_pmd_huge(*pmd)) {
> > - pte = pte_offset_kernel(pmd, addr);
> > - clear_pte_entry(kvm, pte, addr);
> > - next = addr + PAGE_SIZE;
> > - }
> > +static void unmap_puds(struct kvm *kvm, pgd_t *pgd,
> > + unsigned long long addr, unsigned long long end)
> > +{
> > + unsigned long long next, start_addr = addr;
> > + pud_t *pud, *start_pud;
> >
> > - /*
> > - * If the pmd entry is to be cleared, walk back up the ladder
> > - */
> > - if (kvm_pmd_huge(*pmd) || (pte && page_empty(pte))) {
> > - clear_pmd_entry(kvm, pmd, addr);
> > - next = kvm_pmd_addr_end(addr, end);
> > - if (page_empty(pmd) && !page_empty(pud)) {
> > + start_pud = pud = pud_offset(pgd, addr);
> > + do {
> > + next = kvm_pud_addr_end(addr, end);
> > + if (!pud_none(*pud)) {
> > + if (pud_huge(*pid)) {
> > clear_pud_entry(kvm, pud, addr);
> > - next = kvm_pud_addr_end(addr, end);
> > + } else {
> > + unmap_pmds(kvm, pud, addr, next);
> > }
> > }
> > + } while (pud++, addr = next, addr != end);
> >
> > - addr = next;
> > - }
> > + if (kvm_pud_table_empty(start_pud))
> > + clear_pgd_entry(kvm, pgd, start_addr);
> > +}
> > +
> > +
> > +static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
> > + unsigned long long start, u64 size)
> > +{
> > + pgd_t *pgd;
> > + unsigned long long addr = start, end = start + size;
> > + unsigned long long next;
> > +
> > + pgd = pgdp + pgd_index(addr);
> > + do {
> > + next = kvm_pgd_addr_end(addr, end);
> > + unmap_puds(kvm, pgd, addr, next);
> > + } while (pgd++, addr = next, addr != end);
> > }
> >
> > static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
> > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> > index 7d29847..8e138c7 100644
> > --- a/arch/arm64/include/asm/kvm_mmu.h
> > +++ b/arch/arm64/include/asm/kvm_mmu.h
> > @@ -125,6 +125,21 @@ static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
> > #define kvm_pud_addr_end(addr, end) pud_addr_end(addr, end)
> > #define kvm_pmd_addr_end(addr, end) pmd_addr_end(addr, end)
> >
> > +static inline bool kvm_page_empty(void *ptr)
> > +{
> > + struct page *ptr_page = virt_to_page(ptr);
> > + return page_count(ptr_page) == 1;
> > +}
> > +
> > +#define kvm_pte_table_empty(ptep) kvm_page_empty(ptep)
> > +#ifndef CONFIG_ARM64_64K_PAGES
> > +#define kvm_pmd_table_empty(pmdp) kvm_page_empty(pmdp)
> > +#else
> > +#define kvm_pmd_table_empty(pmdp) (0)
> > +#endif
> > +#define kvm_pud_table_empty(pudp) (0)
> > +
> > +
> > struct kvm;
> >
> > #define kvm_flush_dcache_to_poc(a,l) __flush_dcache_area((a), (l))
> >
>
> Other than the odd __unused, looks pretty good. I gave it a quick go on
> my dual A7 rig, and it did worked nicely.
Forgot to say that I tested it using various
provoking-a-lot-of-unmapping operations on my TC2 and the v8 Foundation
Model with and without THP configured, and it works.
>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>
Thanks!
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