Messages in this thread | | | Subject | Re: [PATCH v4 4/7] KVM: arm64: Support PUD hugepage in stage2_is_exec() | From | Suzuki K Poulose <> | Date | Thu, 5 Jul 2018 17:48:37 +0100 |
| |
Hi Punit,
On 05/07/18 15:08, Punit Agrawal wrote: > In preparation for creating PUD hugepages at stage 2, add support for > detecting execute permissions on PUD page table entries. Faults due to > lack of execute permissions on page table entries is used to perform > i-cache invalidation on first execute. > > Provide trivial implementations of arm32 helpers to allow sharing of > code. > > Signed-off-by: Punit Agrawal <punit.agrawal@arm.com> > Cc: Christoffer Dall <christoffer.dall@arm.com> > Cc: Marc Zyngier <marc.zyngier@arm.com> > Cc: Russell King <linux@armlinux.org.uk> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > --- > arch/arm/include/asm/kvm_mmu.h | 6 ++++++ > arch/arm64/include/asm/kvm_mmu.h | 5 +++++ > arch/arm64/include/asm/pgtable-hwdef.h | 2 ++ > virt/kvm/arm/mmu.c | 10 +++++++++- > 4 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h > index c23722f75d5c..d05c8986e495 100644 > --- a/arch/arm/include/asm/kvm_mmu.h > +++ b/arch/arm/include/asm/kvm_mmu.h > @@ -96,6 +96,12 @@ static inline bool kvm_s2pud_readonly(pud_t *pud) > } > > > +static inline bool kvm_s2pud_exec(pud_t *pud) > +{ > + BUG(); > + return false; > +} > + > static inline void kvm_set_pmd(pmd_t *pmd, pmd_t new_pmd) > { > *pmd = new_pmd; > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h > index 84051930ddfe..15bc1be8f82f 100644 > --- a/arch/arm64/include/asm/kvm_mmu.h > +++ b/arch/arm64/include/asm/kvm_mmu.h > @@ -249,6 +249,11 @@ static inline bool kvm_s2pud_readonly(pud_t *pudp) > return kvm_s2pte_readonly((pte_t *)pudp); > } > > +static inline bool kvm_s2pud_exec(pud_t *pudp) > +{ > + return !(READ_ONCE(pud_val(*pudp)) & PUD_S2_XN); > +} > + > static inline bool kvm_page_empty(void *ptr) > { > struct page *ptr_page = virt_to_page(ptr); > diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h > index fd208eac9f2a..10ae592b78b8 100644 > --- a/arch/arm64/include/asm/pgtable-hwdef.h > +++ b/arch/arm64/include/asm/pgtable-hwdef.h > @@ -193,6 +193,8 @@ > #define PMD_S2_RDWR (_AT(pmdval_t, 3) << 6) /* HAP[2:1] */ > #define PMD_S2_XN (_AT(pmdval_t, 2) << 53) /* XN[1:0] */ > > +#define PUD_S2_XN (_AT(pudval_t, 2) << 53) /* XN[1:0] */ > +
The changes above look good to me. Please see below.
> /* > * Memory Attribute override for Stage-2 (MemAttr[3:0]) > */ > diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c > index db04b18218c1..ccdea0edabb3 100644 > --- a/virt/kvm/arm/mmu.c > +++ b/virt/kvm/arm/mmu.c > @@ -1040,10 +1040,18 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache > > static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr) > { > + pud_t *pudp; > pmd_t *pmdp; > pte_t *ptep; > > - pmdp = stage2_get_pmd(kvm, NULL, addr); > + pudp = stage2_get_pud(kvm, NULL, addr); > + if (!pudp || pud_none(*pudp) || !pud_present(*pudp)) > + return false; > + > + if (pud_huge(*pudp)) > + return kvm_s2pud_exec(pudp); > + > + pmdp = stage2_pmd_offset(pudp, addr); > if (!pmdp || pmd_none(*pmdp) || !pmd_present(*pmdp)) > return false;
I am wondering if we need a slightly better way to deal with this kind of operation. We seem to duplicate the above operation (here and in the following patches), i.e, finding the "leaf entry" for a given address and follow the checks one level up at a time.
So instead of doing, stage2_get_pud() and walking down everywhere this is needed, how about adding :
/* Returns true if the leaf entry is found and updates the relevant pointer */ found = stage2_get_leaf_entry(kvm, NULL, addr, &pudp, &pmdp, &ptep)
which could set the appropriate entry and we could check the result here.
Cheers Suzuki
| |