[PATCH 2/2] KVM: RISC-V: Use common KVM implementation of MMU memory caches
Anup Patel
anup at brainfault.org
Mon Nov 22 21:14:52 PST 2021
On Thu, Nov 4, 2021 at 10:11 PM Sean Christopherson <seanjc at google.com> wrote:
>
> Use common KVM's implementation of the MMU memory caches, which for all
> intents and purposes is semantically identical to RISC-V's version, the
> only difference being that the common implementation will fall back to an
> atomic allocation if there's a KVM bug that triggers a cache underflow.
>
> RISC-V appears to have based its MMU code on arm64 before the conversion
> to the common caches in commit c1a33aebe91d ("KVM: arm64: Use common KVM
> implementation of MMU memory caches"), despite having also copy-pasted
> the definition of KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE in kvm_types.h.
Yes, I missed moving to common KVM memory cache APIs in the recent revisions
of the KVM RISC-V series. Thanks for this patch.
>
> Opportunistically drop the superfluous wrapper
> kvm_riscv_stage2_flush_cache(), whose name is very, very confusing as
> "cache flush" in the context of MMU code almost always refers to flushing
> hardware caches, not freeing unused software objects.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc at google.com>
I have queued this for 5.17.
Thanks,
Anup
> ---
> arch/riscv/include/asm/kvm_host.h | 10 +----
> arch/riscv/include/asm/kvm_types.h | 2 +-
> arch/riscv/kvm/mmu.c | 64 +++++-------------------------
> arch/riscv/kvm/vcpu.c | 5 ++-
> 4 files changed, 16 insertions(+), 65 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 25ba21f98504..37589b953bcb 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -79,13 +79,6 @@ struct kvm_sbi_context {
> int return_handled;
> };
>
> -#define KVM_MMU_PAGE_CACHE_NR_OBJS 32
> -
> -struct kvm_mmu_page_cache {
> - int nobjs;
> - void *objects[KVM_MMU_PAGE_CACHE_NR_OBJS];
> -};
> -
> struct kvm_cpu_trap {
> unsigned long sepc;
> unsigned long scause;
> @@ -195,7 +188,7 @@ struct kvm_vcpu_arch {
> struct kvm_sbi_context sbi_context;
>
> /* Cache pages needed to program page tables with spinlock held */
> - struct kvm_mmu_page_cache mmu_page_cache;
> + struct kvm_mmu_memory_cache mmu_page_cache;
>
> /* VCPU power-off state */
> bool power_off;
> @@ -223,7 +216,6 @@ void __kvm_riscv_hfence_gvma_all(void);
> int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
> struct kvm_memory_slot *memslot,
> gpa_t gpa, unsigned long hva, bool is_write);
> -void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu);
> int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm);
> void kvm_riscv_stage2_free_pgd(struct kvm *kvm);
> void kvm_riscv_stage2_update_hgatp(struct kvm_vcpu *vcpu);
> diff --git a/arch/riscv/include/asm/kvm_types.h b/arch/riscv/include/asm/kvm_types.h
> index e476b404eb67..e15765f98d7a 100644
> --- a/arch/riscv/include/asm/kvm_types.h
> +++ b/arch/riscv/include/asm/kvm_types.h
> @@ -2,6 +2,6 @@
> #ifndef _ASM_RISCV_KVM_TYPES_H
> #define _ASM_RISCV_KVM_TYPES_H
>
> -#define KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE 40
> +#define KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE 32
>
> #endif /* _ASM_RISCV_KVM_TYPES_H */
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index fc058ff5f4b6..b8b902b08deb 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -83,43 +83,6 @@ static int stage2_level_to_page_size(u32 level, unsigned long *out_pgsize)
> return 0;
> }
>
> -static int stage2_cache_topup(struct kvm_mmu_page_cache *pcache,
> - int min, int max)
> -{
> - void *page;
> -
> - BUG_ON(max > KVM_MMU_PAGE_CACHE_NR_OBJS);
> - if (pcache->nobjs >= min)
> - return 0;
> - while (pcache->nobjs < max) {
> - page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> - if (!page)
> - return -ENOMEM;
> - pcache->objects[pcache->nobjs++] = page;
> - }
> -
> - return 0;
> -}
> -
> -static void stage2_cache_flush(struct kvm_mmu_page_cache *pcache)
> -{
> - while (pcache && pcache->nobjs)
> - free_page((unsigned long)pcache->objects[--pcache->nobjs]);
> -}
> -
> -static void *stage2_cache_alloc(struct kvm_mmu_page_cache *pcache)
> -{
> - void *p;
> -
> - if (!pcache)
> - return NULL;
> -
> - BUG_ON(!pcache->nobjs);
> - p = pcache->objects[--pcache->nobjs];
> -
> - return p;
> -}
> -
> static bool stage2_get_leaf_entry(struct kvm *kvm, gpa_t addr,
> pte_t **ptepp, u32 *ptep_level)
> {
> @@ -171,7 +134,7 @@ static void stage2_remote_tlb_flush(struct kvm *kvm, u32 level, gpa_t addr)
> }
>
> static int stage2_set_pte(struct kvm *kvm, u32 level,
> - struct kvm_mmu_page_cache *pcache,
> + struct kvm_mmu_memory_cache *pcache,
> gpa_t addr, const pte_t *new_pte)
> {
> u32 current_level = stage2_pgd_levels - 1;
> @@ -186,7 +149,7 @@ static int stage2_set_pte(struct kvm *kvm, u32 level,
> return -EEXIST;
>
> if (!pte_val(*ptep)) {
> - next_ptep = stage2_cache_alloc(pcache);
> + next_ptep = kvm_mmu_memory_cache_alloc(pcache);
> if (!next_ptep)
> return -ENOMEM;
> *ptep = pfn_pte(PFN_DOWN(__pa(next_ptep)),
> @@ -209,7 +172,7 @@ static int stage2_set_pte(struct kvm *kvm, u32 level,
> }
>
> static int stage2_map_page(struct kvm *kvm,
> - struct kvm_mmu_page_cache *pcache,
> + struct kvm_mmu_memory_cache *pcache,
> gpa_t gpa, phys_addr_t hpa,
> unsigned long page_size,
> bool page_rdonly, bool page_exec)
> @@ -384,7 +347,10 @@ static int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
> int ret = 0;
> unsigned long pfn;
> phys_addr_t addr, end;
> - struct kvm_mmu_page_cache pcache = { 0, };
> + struct kvm_mmu_memory_cache pcache;
> +
> + memset(&pcache, 0, sizeof(pcache));
> + pcache.gfp_zero = __GFP_ZERO;
>
> end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
> pfn = __phys_to_pfn(hpa);
> @@ -395,9 +361,7 @@ static int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
> if (!writable)
> pte = pte_wrprotect(pte);
>
> - ret = stage2_cache_topup(&pcache,
> - stage2_pgd_levels,
> - KVM_MMU_PAGE_CACHE_NR_OBJS);
> + ret = kvm_mmu_topup_memory_cache(&pcache, stage2_pgd_levels);
> if (ret)
> goto out;
>
> @@ -411,7 +375,7 @@ static int stage2_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
> }
>
> out:
> - stage2_cache_flush(&pcache);
> + kvm_mmu_free_memory_cache(&pcache);
> return ret;
> }
>
> @@ -646,7 +610,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
> gfn_t gfn = gpa >> PAGE_SHIFT;
> struct vm_area_struct *vma;
> struct kvm *kvm = vcpu->kvm;
> - struct kvm_mmu_page_cache *pcache = &vcpu->arch.mmu_page_cache;
> + struct kvm_mmu_memory_cache *pcache = &vcpu->arch.mmu_page_cache;
> bool logging = (memslot->dirty_bitmap &&
> !(memslot->flags & KVM_MEM_READONLY)) ? true : false;
> unsigned long vma_pagesize, mmu_seq;
> @@ -681,8 +645,7 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
> }
>
> /* We need minimum second+third level pages */
> - ret = stage2_cache_topup(pcache, stage2_pgd_levels,
> - KVM_MMU_PAGE_CACHE_NR_OBJS);
> + ret = kvm_mmu_topup_memory_cache(pcache, stage2_pgd_levels);
> if (ret) {
> kvm_err("Failed to topup stage2 cache\n");
> return ret;
> @@ -731,11 +694,6 @@ int kvm_riscv_stage2_map(struct kvm_vcpu *vcpu,
> return ret;
> }
>
> -void kvm_riscv_stage2_flush_cache(struct kvm_vcpu *vcpu)
> -{
> - stage2_cache_flush(&vcpu->arch.mmu_page_cache);
> -}
> -
> int kvm_riscv_stage2_alloc_pgd(struct kvm *kvm)
> {
> struct page *pgd_page;
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index e3d3aed46184..a50abe400ea8 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -77,6 +77,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>
> /* Mark this VCPU never ran */
> vcpu->arch.ran_atleast_once = false;
> + vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
>
> /* Setup ISA features available to VCPU */
> vcpu->arch.isa = riscv_isa_extension_base(NULL) & KVM_RISCV_ISA_ALLOWED;
> @@ -107,8 +108,8 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> /* Cleanup VCPU timer */
> kvm_riscv_vcpu_timer_deinit(vcpu);
>
> - /* Flush the pages pre-allocated for Stage2 page table mappings */
> - kvm_riscv_stage2_flush_cache(vcpu);
> + /* Free unused pages pre-allocated for Stage2 page table mappings */
> + kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
> }
>
> int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
> --
> 2.34.0.rc0.344.g81b53c2807-goog
>
>
> --
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