From c353fde17d8f7e710884532da50393cd22ddbfbe Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Wed, 21 May 2025 13:48:34 +0100 Subject: [PATCH] KVM: arm64: np-guest CMOs with PMD_SIZE fixmap With the introduction of stage-2 huge mappings in the pKVM hypervisor, guest pages CMO is needed for PMD_SIZE size. Fixmap only supports PAGE_SIZE and iterating over the huge-page is time consuming (mostly due to TLBI on hyp_fixmap_unmap) which is a problem for EL2 latency. Introduce a shared PMD_SIZE fixmap (hyp_fixblock_map/hyp_fixblock_unmap) to improve guest page CMOs when stage-2 huge mappings are installed. On a Pixel6, the iterative solution resulted in a latency of ~700us, while the PMD_SIZE fixmap reduces it to ~100us. Because of the horrendous private range allocation that would be necessary, this is disabled for 64KiB pages systems. Suggested-by: Quentin Perret Signed-off-by: Vincent Donnefort Signed-off-by: Quentin Perret Link: https://lore.kernel.org/r/20250521124834.1070650-11-vdonnefort@google.com Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_pgtable.h | 5 ++ arch/arm64/kvm/hyp/include/nvhe/mm.h | 4 +- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 42 +++++++----- arch/arm64/kvm/hyp/nvhe/mm.c | 97 ++++++++++++++++++++++++--- arch/arm64/kvm/hyp/nvhe/setup.c | 2 +- arch/arm64/kvm/hyp/pgtable.c | 6 -- 6 files changed, 123 insertions(+), 33 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 1b43bcd2a679..2888b5d03757 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -59,6 +59,11 @@ typedef u64 kvm_pte_t; #define KVM_PHYS_INVALID (-1ULL) +#define KVM_PTE_TYPE BIT(1) +#define KVM_PTE_TYPE_BLOCK 0 +#define KVM_PTE_TYPE_PAGE 1 +#define KVM_PTE_TYPE_TABLE 1 + #define KVM_PTE_LEAF_ATTR_LO GENMASK(11, 2) #define KVM_PTE_LEAF_ATTR_LO_S1_ATTRIDX GENMASK(4, 2) diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h index 230e4f2527de..6e83ce35c2f2 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h @@ -13,9 +13,11 @@ extern struct kvm_pgtable pkvm_pgtable; extern hyp_spinlock_t pkvm_pgd_lock; -int hyp_create_pcpu_fixmap(void); +int hyp_create_fixmap(void); void *hyp_fixmap_map(phys_addr_t phys); void hyp_fixmap_unmap(void); +void *hyp_fixblock_map(phys_addr_t phys, size_t *size); +void hyp_fixblock_unmap(void); int hyp_create_idmap(u32 hyp_va_bits); int hyp_map_vectors(void); diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 1490820b9ebe..e359cd24ecf0 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -216,34 +216,42 @@ static void guest_s2_put_page(void *addr) hyp_put_page(¤t_vm->pool, addr); } -static void clean_dcache_guest_page(void *va, size_t size) +static void __apply_guest_page(void *va, size_t size, + void (*func)(void *addr, size_t size)) { size += va - PTR_ALIGN_DOWN(va, PAGE_SIZE); va = PTR_ALIGN_DOWN(va, PAGE_SIZE); size = PAGE_ALIGN(size); while (size) { - __clean_dcache_guest_page(hyp_fixmap_map(__hyp_pa(va)), - PAGE_SIZE); - hyp_fixmap_unmap(); - va += PAGE_SIZE; - size -= PAGE_SIZE; + size_t map_size = PAGE_SIZE; + void *map; + + if (IS_ALIGNED((unsigned long)va, PMD_SIZE) && size >= PMD_SIZE) + map = hyp_fixblock_map(__hyp_pa(va), &map_size); + else + map = hyp_fixmap_map(__hyp_pa(va)); + + func(map, map_size); + + if (map_size == PMD_SIZE) + hyp_fixblock_unmap(); + else + hyp_fixmap_unmap(); + + size -= map_size; + va += map_size; } } -static void invalidate_icache_guest_page(void *va, size_t size) +static void clean_dcache_guest_page(void *va, size_t size) { - size += va - PTR_ALIGN_DOWN(va, PAGE_SIZE); - va = PTR_ALIGN_DOWN(va, PAGE_SIZE); - size = PAGE_ALIGN(size); + __apply_guest_page(va, size, __clean_dcache_guest_page); +} - while (size) { - __invalidate_icache_guest_page(hyp_fixmap_map(__hyp_pa(va)), - PAGE_SIZE); - hyp_fixmap_unmap(); - va += PAGE_SIZE; - size -= PAGE_SIZE; - } +static void invalidate_icache_guest_page(void *va, size_t size) +{ + __apply_guest_page(va, size, __invalidate_icache_guest_page); } int kvm_guest_prepare_stage2(struct pkvm_hyp_vm *vm, void *pgd) diff --git a/arch/arm64/kvm/hyp/nvhe/mm.c b/arch/arm64/kvm/hyp/nvhe/mm.c index f41c7440b34b..ae8391baebc3 100644 --- a/arch/arm64/kvm/hyp/nvhe/mm.c +++ b/arch/arm64/kvm/hyp/nvhe/mm.c @@ -229,9 +229,8 @@ int hyp_map_vectors(void) return 0; } -void *hyp_fixmap_map(phys_addr_t phys) +static void *fixmap_map_slot(struct hyp_fixmap_slot *slot, phys_addr_t phys) { - struct hyp_fixmap_slot *slot = this_cpu_ptr(&fixmap_slots); kvm_pte_t pte, *ptep = slot->ptep; pte = *ptep; @@ -243,10 +242,21 @@ void *hyp_fixmap_map(phys_addr_t phys) return (void *)slot->addr; } +void *hyp_fixmap_map(phys_addr_t phys) +{ + return fixmap_map_slot(this_cpu_ptr(&fixmap_slots), phys); +} + static void fixmap_clear_slot(struct hyp_fixmap_slot *slot) { kvm_pte_t *ptep = slot->ptep; u64 addr = slot->addr; + u32 level; + + if (FIELD_GET(KVM_PTE_TYPE, *ptep) == KVM_PTE_TYPE_PAGE) + level = KVM_PGTABLE_LAST_LEVEL; + else + level = KVM_PGTABLE_LAST_LEVEL - 1; /* create_fixblock() guarantees PMD level */ WRITE_ONCE(*ptep, *ptep & ~KVM_PTE_VALID); @@ -260,7 +270,7 @@ static void fixmap_clear_slot(struct hyp_fixmap_slot *slot) * https://lore.kernel.org/kvm/20221017115209.2099-1-will@kernel.org/T/#mf10dfbaf1eaef9274c581b81c53758918c1d0f03 */ dsb(ishst); - __tlbi_level(vale2is, __TLBI_VADDR(addr, 0), KVM_PGTABLE_LAST_LEVEL); + __tlbi_level(vale2is, __TLBI_VADDR(addr, 0), level); dsb(ish); isb(); } @@ -273,9 +283,9 @@ void hyp_fixmap_unmap(void) static int __create_fixmap_slot_cb(const struct kvm_pgtable_visit_ctx *ctx, enum kvm_pgtable_walk_flags visit) { - struct hyp_fixmap_slot *slot = per_cpu_ptr(&fixmap_slots, (u64)ctx->arg); + struct hyp_fixmap_slot *slot = (struct hyp_fixmap_slot *)ctx->arg; - if (!kvm_pte_valid(ctx->old) || ctx->level != KVM_PGTABLE_LAST_LEVEL) + if (!kvm_pte_valid(ctx->old) || (ctx->end - ctx->start) != kvm_granule_size(ctx->level)) return -EINVAL; slot->addr = ctx->addr; @@ -296,13 +306,84 @@ static int create_fixmap_slot(u64 addr, u64 cpu) struct kvm_pgtable_walker walker = { .cb = __create_fixmap_slot_cb, .flags = KVM_PGTABLE_WALK_LEAF, - .arg = (void *)cpu, + .arg = per_cpu_ptr(&fixmap_slots, cpu), }; return kvm_pgtable_walk(&pkvm_pgtable, addr, PAGE_SIZE, &walker); } -int hyp_create_pcpu_fixmap(void) +#if PAGE_SHIFT < 16 +#define HAS_FIXBLOCK +static struct hyp_fixmap_slot hyp_fixblock_slot; +static DEFINE_HYP_SPINLOCK(hyp_fixblock_lock); +#endif + +static int create_fixblock(void) +{ +#ifdef HAS_FIXBLOCK + struct kvm_pgtable_walker walker = { + .cb = __create_fixmap_slot_cb, + .flags = KVM_PGTABLE_WALK_LEAF, + .arg = &hyp_fixblock_slot, + }; + unsigned long addr; + phys_addr_t phys; + int ret, i; + + /* Find a RAM phys address, PMD aligned */ + for (i = 0; i < hyp_memblock_nr; i++) { + phys = ALIGN(hyp_memory[i].base, PMD_SIZE); + if (phys + PMD_SIZE < (hyp_memory[i].base + hyp_memory[i].size)) + break; + } + + if (i >= hyp_memblock_nr) + return -EINVAL; + + hyp_spin_lock(&pkvm_pgd_lock); + addr = ALIGN(__io_map_base, PMD_SIZE); + ret = __pkvm_alloc_private_va_range(addr, PMD_SIZE); + if (ret) + goto unlock; + + ret = kvm_pgtable_hyp_map(&pkvm_pgtable, addr, PMD_SIZE, phys, PAGE_HYP); + if (ret) + goto unlock; + + ret = kvm_pgtable_walk(&pkvm_pgtable, addr, PMD_SIZE, &walker); + +unlock: + hyp_spin_unlock(&pkvm_pgd_lock); + + return ret; +#else + return 0; +#endif +} + +void *hyp_fixblock_map(phys_addr_t phys, size_t *size) +{ +#ifdef HAS_FIXBLOCK + *size = PMD_SIZE; + hyp_spin_lock(&hyp_fixblock_lock); + return fixmap_map_slot(&hyp_fixblock_slot, phys); +#else + *size = PAGE_SIZE; + return hyp_fixmap_map(phys); +#endif +} + +void hyp_fixblock_unmap(void) +{ +#ifdef HAS_FIXBLOCK + fixmap_clear_slot(&hyp_fixblock_slot); + hyp_spin_unlock(&hyp_fixblock_lock); +#else + hyp_fixmap_unmap(); +#endif +} + +int hyp_create_fixmap(void) { unsigned long addr, i; int ret; @@ -322,7 +403,7 @@ int hyp_create_pcpu_fixmap(void) return ret; } - return 0; + return create_fixblock(); } int hyp_create_idmap(u32 hyp_va_bits) diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c index c19860fc8183..a48d3f5a5afb 100644 --- a/arch/arm64/kvm/hyp/nvhe/setup.c +++ b/arch/arm64/kvm/hyp/nvhe/setup.c @@ -312,7 +312,7 @@ void __noreturn __pkvm_init_finalise(void) if (ret) goto out; - ret = hyp_create_pcpu_fixmap(); + ret = hyp_create_fixmap(); if (ret) goto out; diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index df5cc74a7dd0..c351b4abd5db 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -11,12 +11,6 @@ #include #include - -#define KVM_PTE_TYPE BIT(1) -#define KVM_PTE_TYPE_BLOCK 0 -#define KVM_PTE_TYPE_PAGE 1 -#define KVM_PTE_TYPE_TABLE 1 - struct kvm_pgtable_walk_data { struct kvm_pgtable_walker *walker; -- 2.50.1