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Date: Mon, 3 Dec 2018 21:16:54 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Punit Agrawal <punit.agrawal@....com>, kvmarm@...ts.cs.columbia.edu
Cc: suzuki.poulose@....com, marc.zyngier@....com,
Catalin Marinas <catalin.marinas@....com>, will.deacon@....com,
linux-kernel@...r.kernel.org,
Christoffer Dall <christoffer.dall@....com>,
punitagrawal@...il.com, Russell King <linux@...linux.org.uk>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 8/8] KVM: arm64: Add support for creating PUD hugepages
at stage 2
On 10/31/2018 11:27 PM, Punit Agrawal wrote:
> KVM only supports PMD hugepages at stage 2. Now that the various page
> handling routines are updated, extend the stage 2 fault handling to
> map in PUD hugepages.
>
> Addition of PUD hugepage support enables additional page sizes (e.g.,
> 1G with 4K granule) which can be useful on cores that support mapping
> larger block sizes in the TLB entries.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Reviewed-by: Suzuki Poulose <suzuki.poulose@....com>
> Cc: Christoffer Dall <christoffer.dall@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> ---
> arch/arm/include/asm/kvm_mmu.h | 20 +++++
> arch/arm/include/asm/stage2_pgtable.h | 5 ++
> arch/arm64/include/asm/kvm_mmu.h | 16 ++++
> arch/arm64/include/asm/pgtable-hwdef.h | 2 +
> arch/arm64/include/asm/pgtable.h | 2 +
> virt/kvm/arm/mmu.c | 104 +++++++++++++++++++++++--
> 6 files changed, 143 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index e62f0913ce7d..6336319a0d5b 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -84,11 +84,14 @@ void kvm_clear_hyp_idmap(void);
>
> #define kvm_pfn_pte(pfn, prot) pfn_pte(pfn, prot)
> #define kvm_pfn_pmd(pfn, prot) pfn_pmd(pfn, prot)
> +#define kvm_pfn_pud(pfn, prot) (__pud(0))
This makes sense. Was not enabled before and getting added here.
>
> #define kvm_pud_pfn(pud) ({ BUG(); 0; })
>
>
> #define kvm_pmd_mkhuge(pmd) pmd_mkhuge(pmd)
> +/* No support for pud hugepages */
> +#define kvm_pud_mkhuge(pud) ( {BUG(); pud; })
>
> /*
> * The following kvm_*pud*() functions are provided strictly to allow
> @@ -105,6 +108,23 @@ static inline bool kvm_s2pud_readonly(pud_t *pud)
> return false;
> }
>
> +static inline void kvm_set_pud(pud_t *pud, pud_t new_pud)
> +{
> + BUG();
> +}
> +
> +static inline pud_t kvm_s2pud_mkwrite(pud_t pud)
> +{
> + BUG();
> + return pud;
> +}
> +
> +static inline pud_t kvm_s2pud_mkexec(pud_t pud)
> +{
> + BUG();
> + return pud;
> +}
> +
But the previous patches have been adding some of these helpers
as well. Needs consolidation.
> static inline bool kvm_s2pud_exec(pud_t *pud)
> {
> BUG();
> diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h
> index f6a7ea805232..f9017167a8d1 100644
> --- a/arch/arm/include/asm/stage2_pgtable.h
> +++ b/arch/arm/include/asm/stage2_pgtable.h
> @@ -68,4 +68,9 @@ stage2_pmd_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> #define stage2_pmd_table_empty(kvm, pmdp) kvm_page_empty(pmdp)
> #define stage2_pud_table_empty(kvm, pudp) false
>
> +static inline bool kvm_stage2_has_pud(struct kvm *kvm)
> +{
> + return false;
> +}
>
Makes sense. Disabled on arm32.
+
> #endif /* __ARM_S2_PGTABLE_H_ */
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 9f941f70775c..8af4b1befa42 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -184,12 +184,16 @@ void kvm_clear_hyp_idmap(void);
> #define kvm_mk_pgd(pudp) \
> __pgd(__phys_to_pgd_val(__pa(pudp)) | PUD_TYPE_TABLE)
>
> +#define kvm_set_pud(pudp, pud) set_pud(pudp, pud)
> +
> #define kvm_pfn_pte(pfn, prot) pfn_pte(pfn, prot)
> #define kvm_pfn_pmd(pfn, prot) pfn_pmd(pfn, prot)
> +#define kvm_pfn_pud(pfn, prot) pfn_pud(pfn, prot)
>
> #define kvm_pud_pfn(pud) pud_pfn(pud)
>
> #define kvm_pmd_mkhuge(pmd) pmd_mkhuge(pmd)
> +#define kvm_pud_mkhuge(pud) pud_mkhuge(pud)
>
> static inline pte_t kvm_s2pte_mkwrite(pte_t pte)
> {
> @@ -203,6 +207,12 @@ static inline pmd_t kvm_s2pmd_mkwrite(pmd_t pmd)
> return pmd;
> }
>
> +static inline pud_t kvm_s2pud_mkwrite(pud_t pud)
> +{
> + pud_val(pud) |= PUD_S2_RDWR;
> + return pud;
> +}
> +
> static inline pte_t kvm_s2pte_mkexec(pte_t pte)
> {
> pte_val(pte) &= ~PTE_S2_XN;
> @@ -215,6 +225,12 @@ static inline pmd_t kvm_s2pmd_mkexec(pmd_t pmd)
> return pmd;
> }
>
> +static inline pud_t kvm_s2pud_mkexec(pud_t pud)
> +{
> + pud_val(pud) &= ~PUD_S2_XN;
> + return pud;
> +}
> +
Should not these be consolidated in previous patches ?
> static inline void kvm_set_s2pte_readonly(pte_t *ptep)
> {
> pteval_t old_pteval, pteval;
> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
> index 336e24cddc87..6f1c187f1c86 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_RDONLY (_AT(pudval_t, 1) << 6) /* HAP[2:1] */
> +#define PUD_S2_RDWR (_AT(pudval_t, 3) << 6) /* HAP[2:1] */
> #define PUD_S2_XN (_AT(pudval_t, 2) << 53) /* XN[1:0] */
All PUD related HW page table definitions should have been added
at once in one of the preparatory patches.
>
> /*
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index bb0f3f17a7a9..576128635f3c 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -390,6 +390,8 @@ static inline int pmd_protnone(pmd_t pmd)
> #define pud_mkyoung(pud) pte_pud(pte_mkyoung(pud_pte(pud)))
> #define pud_write(pud) pte_write(pud_pte(pud))
>
> +#define pud_mkhuge(pud) (__pud(pud_val(pud) & ~PUD_TABLE_BIT))
> +
All new pud_* definitions should have come together at once as well.
> #define __pud_to_phys(pud) __pte_to_phys(pud_pte(pud))
> #define __phys_to_pud_val(phys) __phys_to_pte_val(phys)
> #define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 3893ea6a50bf..2dcff38868d4 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -115,6 +115,25 @@ static void stage2_dissolve_pmd(struct kvm *kvm, phys_addr_t addr, pmd_t *pmd)
> put_page(virt_to_page(pmd));
> }
>
> +/**
> + * stage2_dissolve_pud() - clear and flush huge PUD entry
> + * @kvm: pointer to kvm structure.
> + * @addr: IPA
> + * @pud: pud pointer for IPA
> + *
> + * Function clears a PUD entry, flushes addr 1st and 2nd stage TLBs. Marks all
> + * pages in the range dirty.
> + */
> +static void stage2_dissolve_pud(struct kvm *kvm, phys_addr_t addr, pud_t *pudp)
> +{
> + if (!stage2_pud_huge(kvm, *pudp))
> + return;
> +
> + stage2_pud_clear(kvm, pudp);
> + kvm_tlb_flush_vmid_ipa(kvm, addr);
> + put_page(virt_to_page(pudp));
> +}
> +
> static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
> int min, int max)
> {
> @@ -1022,7 +1041,7 @@ static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
> pmd_t *pmd;
>
> pud = stage2_get_pud(kvm, cache, addr);
> - if (!pud)
> + if (!pud || stage2_pud_huge(kvm, *pud))
> return NULL;
>
> if (stage2_pud_none(kvm, *pud)) {
> @@ -1083,6 +1102,36 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
> return 0;
> }
>
> +static int stage2_set_pud_huge(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
> + phys_addr_t addr, const pud_t *new_pudp)
> +{
> + pud_t *pudp, old_pud;
> +
> + pudp = stage2_get_pud(kvm, cache, addr);
> + VM_BUG_ON(!pudp);
> +
> + old_pud = *pudp;
> +
> + /*
> + * A large number of vcpus faulting on the same stage 2 entry,
> + * can lead to a refault due to the
> + * stage2_pud_clear()/tlb_flush(). Skip updating the page
> + * tables if there is no change.
> + */
> + if (pud_val(old_pud) == pud_val(*new_pudp))
> + return 0;
> +
> + if (stage2_pud_present(kvm, old_pud)) {
> + stage2_pud_clear(kvm, pudp);
> + kvm_tlb_flush_vmid_ipa(kvm, addr);
> + } else {
> + get_page(virt_to_page(pudp));
> + }
> +
> + kvm_set_pud(pudp, *new_pudp);
> + return 0;
> +}
> +
> /*
> * stage2_get_leaf_entry - walk the stage2 VM page tables and return
> * true if a valid and present leaf-entry is found. A pointer to the
> @@ -1149,6 +1198,7 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
> phys_addr_t addr, const pte_t *new_pte,
> unsigned long flags)
> {
> + pud_t *pud;
> pmd_t *pmd;
> pte_t *pte, old_pte;
> bool iomap = flags & KVM_S2PTE_FLAG_IS_IOMAP;
> @@ -1157,7 +1207,31 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
> VM_BUG_ON(logging_active && !cache);
>
> /* Create stage-2 page table mapping - Levels 0 and 1 */
> - pmd = stage2_get_pmd(kvm, cache, addr);
> + pud = stage2_get_pud(kvm, cache, addr);
> + if (!pud) {
> + /*
> + * Ignore calls from kvm_set_spte_hva for unallocated
> + * address ranges.
> + */
> + return 0;
> + }
> +
> + /*
> + * While dirty page logging - dissolve huge PUD, then continue
> + * on to allocate page.
> + */
> + if (logging_active)
> + stage2_dissolve_pud(kvm, addr, pud);
> +
> + if (stage2_pud_none(kvm, *pud)) {
> + if (!cache)
> + return 0; /* ignore calls from kvm_set_spte_hva */
> + pmd = mmu_memory_cache_alloc(cache);
> + stage2_pud_populate(kvm, pud, pmd);
> + get_page(virt_to_page(pud));
> + }
> +
> + pmd = stage2_pmd_offset(kvm, pud, addr);
> if (!pmd) {
> /*
> * Ignore calls from kvm_set_spte_hva for unallocated
> @@ -1557,12 +1631,19 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> }
>
> vma_pagesize = vma_kernel_pagesize(vma);
> - if (vma_pagesize == PMD_SIZE && !logging_active) {
> - gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
> + /*
> + * PUD level may not exist for a VM but PMD is guaranteed to
> + * exist.
> + */
> + if ((vma_pagesize == PMD_SIZE ||
> + (vma_pagesize == PUD_SIZE && kvm_stage2_has_pud(kvm))) &&
> + !logging_active) {
This can be better and wrapped in a helper. Probably arm64 definition
for the helper should check on (PUD_SIZE || PMD_SIZE) but for arm32
it should just check on PMD_SIZE alone. But this is optional.
> + gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
> } else {
> /*
> * Fallback to PTE if it's not one of the Stage 2
> - * supported hugepage sizes
> + * supported hugepage sizes or the corresponding level
> + * doesn't exist
> */
> vma_pagesize = PAGE_SIZE;
>
> @@ -1661,7 +1742,18 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> needs_exec = exec_fault ||
> (fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
>
> - if (vma_pagesize == PMD_SIZE) {
> + if (vma_pagesize == PUD_SIZE) {
> + pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
> +
> + new_pud = kvm_pud_mkhuge(new_pud);
> + if (writable)
> + new_pud = kvm_s2pud_mkwrite(new_pud);
> +
> + if (needs_exec)
> + new_pud = kvm_s2pud_mkexec(new_pud);
> +
> + ret = stage2_set_pud_huge(kvm, memcache, fault_ipa, &new_pud);
> + } else if (vma_pagesize == PMD_SIZE) {
Ran some memory intensive tests on guests with these patches in place but
will continue experimenting and looking for more details in here.
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