Re: [PATCH v2 17/43] arm64: RME: Allow VMM to set RIPAS

Fuad Tabba
2024-04-25T09:54:00Z

Hi,

On Fri, Apr 12, 2024 at 9:43 AM Steven Price <steven.price@arm.com> wrote:
>
> Each page within the protected region of the realm guest can be marked
> as either RAM or EMPTY. Allow the VMM to control this before the guest
> has started and provide the equivalent functions to change this (with
> the guest's approval) at runtime.
>
> When transitioning from RIPAS RAM (1) to RIPAS EMPTY (0) the memory is
> unmapped from the guest and undelegated allowing the memory to be reused
> by the host. When transitioning to RIPAS RAM the actual population of
> the leaf RTTs is done later on stage 2 fault, however it may be
> necessary to allocate additional RTTs to represent the range requested.
>
> When freeing a block mapping it is necessary to temporarily unfold the
> RTT which requires delegating an extra page to the RMM, this page can
> then be recovered once the contents of the block mapping have been
> freed. A spare, delegated page (spare_page) is used for this purpose.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/include/asm/kvm_rme.h | 16 ++
> arch/arm64/kvm/mmu.c | 8 +-
> arch/arm64/kvm/rme.c | 390 +++++++++++++++++++++++++++++++
> 3 files changed, 411 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
> index 915e76068b00..cc8f81cfc3c0 100644
> --- a/arch/arm64/include/asm/kvm_rme.h
> +++ b/arch/arm64/include/asm/kvm_rme.h
> @@ -96,6 +96,14 @@ void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits);
> int kvm_create_rec(struct kvm_vcpu *vcpu);
> void kvm_destroy_rec(struct kvm_vcpu *vcpu);
>
> +void kvm_realm_unmap_range(struct kvm *kvm,
> + unsigned long ipa,
> + u64 size,
> + bool unmap_private);
> +int realm_set_ipa_state(struct kvm_vcpu *vcpu,
> + unsigned long addr, unsigned long end,
> + unsigned long ripas);
> +
> #define RME_RTT_BLOCK_LEVEL 2
> #define RME_RTT_MAX_LEVEL 3
>
> @@ -114,4 +122,12 @@ static inline unsigned long rme_rtt_level_mapsize(int level)
> return (1UL << RME_RTT_LEVEL_SHIFT(level));
> }
>
> +static inline bool realm_is_addr_protected(struct realm *realm,
> + unsigned long addr)
> +{
> + unsigned int ia_bits = realm->ia_bits;
> +
> + return !(addr & ~(BIT(ia_bits - 1) - 1));
> +}
> +
> #endif
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 46f0c4e80ace..8a7b5449697f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -310,6 +310,7 @@ static void invalidate_icache_guest_page(void *va, size_t size)
> * @start: The intermediate physical base address of the range to unmap
> * @size: The size of the area to unmap
> * @may_block: Whether or not we are permitted to block
> + * @only_shared: If true then protected mappings should not be unmapped
> *
> * Clear a range of stage-2 mappings, lowering the various ref-counts. Must
> * be called while holding mmu_lock (unless for freeing the stage2 pgd before
> @@ -317,7 +318,7 @@ static void invalidate_icache_guest_page(void *va, size_t size)
> * with things behind our backs.
> */
> static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size,
> - bool may_block)
> + bool may_block, bool only_shared)

I found the new added only_shared parameter to be a bit confusing,
since this patch also introduces kvm_realm_unmap_range(..., bool
unmap_private), where unmap_private has a different meaning, which I
think is really unmap_all.. It might be better if the parameter meant
the same thing everywhere. Having helpers to sort this out, similar
to what you have with realm_unmap_range_*() might be even clearer.

Thanks,
/fuad

> {
> struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
> phys_addr_t end = start + size;
> @@ -330,7 +331,7 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64
>
> static void unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size)
> {
> - __unmap_stage2_range(mmu, start, size, true);
> + __unmap_stage2_range(mmu, start, size, true, false);
> }
>
> static void stage2_flush_memslot(struct kvm *kvm,
> @@ -1771,7 +1772,8 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
>
> __unmap_stage2_range(&kvm->arch.mmu, range->start << PAGE_SHIFT,
> (range->end - range->start) << PAGE_SHIFT,
> - range->may_block);
> + range->may_block,
> + range->only_shared);
>
> return false;
> }
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index 629a095bea61..9e5983c51393 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -79,6 +79,12 @@ static phys_addr_t __alloc_delegated_page(struct realm *realm,
> return phys;
> }
>
> +static phys_addr_t alloc_delegated_page(struct realm *realm,
> + struct kvm_mmu_memory_cache *mc)
> +{
> + return __alloc_delegated_page(realm, mc, GFP_KERNEL);
> +}
> +
> static void free_delegated_page(struct realm *realm, phys_addr_t phys)
> {
> if (realm->spare_page == PHYS_ADDR_MAX) {
> @@ -94,6 +100,151 @@ static void free_delegated_page(struct realm *realm, phys_addr_t phys)
> free_page((unsigned long)phys_to_virt(phys));
> }
>
> +static int realm_rtt_create(struct realm *realm,
> + unsigned long addr,
> + int level,
> + phys_addr_t phys)
> +{
> + addr = ALIGN_DOWN(addr, rme_rtt_level_mapsize(level - 1));
> + return rmi_rtt_create(virt_to_phys(realm->rd), phys, addr, level);
> +}
> +
> +static int realm_rtt_fold(struct realm *realm,
> + unsigned long addr,
> + int level,
> + phys_addr_t *rtt_granule)
> +{
> + unsigned long out_rtt;
> + int ret;
> +
> + ret = rmi_rtt_fold(virt_to_phys(realm->rd), addr, level, &out_rtt);
> +
> + if (RMI_RETURN_STATUS(ret) == RMI_SUCCESS && rtt_granule)
> + *rtt_granule = out_rtt;
> +
> + return ret;
> +}
> +
> +static int realm_destroy_protected(struct realm *realm,
> + unsigned long ipa,
> + unsigned long *next_addr)
> +{
> + unsigned long rd = virt_to_phys(realm->rd);
> + unsigned long addr;
> + phys_addr_t rtt;
> + int ret;
> +
> +loop:
> + ret = rmi_data_destroy(rd, ipa, &addr, next_addr);
> + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
> + if (*next_addr > ipa)
> + return 0; /* UNASSIGNED */
> + rtt = alloc_delegated_page(realm, NULL);
> + if (WARN_ON(rtt == PHYS_ADDR_MAX))
> + return -1;
> + /* ASSIGNED - ipa is mapped as a block, so split */
> + ret = realm_rtt_create(realm, ipa,
> + RMI_RETURN_INDEX(ret) + 1, rtt);
> + if (WARN_ON(ret)) {
> + free_delegated_page(realm, rtt);
> + return -1;
> + }
> + /* retry */
> + goto loop;
> + } else if (WARN_ON(ret)) {
> + return -1;
> + }
> + ret = rmi_granule_undelegate(addr);
> +
> + /*
> + * If the undelegate fails then something has gone seriously
> + * wrong: take an extra reference to just leak the page
> + */
> + if (WARN_ON(ret))
> + get_page(phys_to_page(addr));
> +
> + return 0;
> +}
> +
> +static void realm_unmap_range_shared(struct kvm *kvm,
> + int level,
> + unsigned long start,
> + unsigned long end)
> +{
> + struct realm *realm = &kvm->arch.realm;
> + unsigned long rd = virt_to_phys(realm->rd);
> + ssize_t map_size = rme_rtt_level_mapsize(level);
> + unsigned long next_addr, addr;
> + unsigned long shared_bit = BIT(realm->ia_bits - 1);
> +
> + if (WARN_ON(level > RME_RTT_MAX_LEVEL))
> + return;
> +
> + start |= shared_bit;
> + end |= shared_bit;
> +
> + for (addr = start; addr < end; addr = next_addr) {
> + unsigned long align_addr = ALIGN(addr, map_size);
> + int ret;
> +
> + next_addr = ALIGN(addr + 1, map_size);
> +
> + if (align_addr != addr || next_addr > end) {
> + /* Need to recurse deeper */
> + if (addr < align_addr)
> + next_addr = align_addr;
> + realm_unmap_range_shared(kvm, level + 1, addr,
> + min(next_addr, end));
> + continue;
> + }
> +
> + ret = rmi_rtt_unmap_unprotected(rd, addr, level, &next_addr);
> + switch (RMI_RETURN_STATUS(ret)) {
> + case RMI_SUCCESS:
> + break;
> + case RMI_ERROR_RTT:
> + if (next_addr == addr) {
> + next_addr = ALIGN(addr + 1, map_size);
> + realm_unmap_range_shared(kvm, level + 1, addr,
> + next_addr);
> + }
> + break;
> + default:
> + WARN_ON(1);
> + }
> + }
> +}
> +
> +static void realm_unmap_range_private(struct kvm *kvm,
> + unsigned long start,
> + unsigned long end)
> +{
> + struct realm *realm = &kvm->arch.realm;
> + ssize_t map_size = RME_PAGE_SIZE;
> + unsigned long next_addr, addr;
> +
> + for (addr = start; addr < end; addr = next_addr) {
> + int ret;
> +
> + next_addr = ALIGN(addr + 1, map_size);
> +
> + ret = realm_destroy_protected(realm, addr, &next_addr);
> +
> + if (WARN_ON(ret))
> + break;
> + }
> +}
> +
> +static void realm_unmap_range(struct kvm *kvm,
> + unsigned long start,
> + unsigned long end,
> + bool unmap_private)
> +{
> + realm_unmap_range_shared(kvm, RME_RTT_MAX_LEVEL - 1, start, end);
> + if (unmap_private)
> + realm_unmap_range_private(kvm, start, end);
> +}
> +
> u32 kvm_realm_ipa_limit(void)
> {
> return u64_get_bits(rmm_feat_reg0, RMI_FEATURE_REGISTER_0_S2SZ);
> @@ -190,6 +341,30 @@ static int realm_rtt_destroy(struct realm *realm, unsigned long addr,
> return ret;
> }
>
> +static int realm_create_rtt_levels(struct realm *realm,
> + unsigned long ipa,
> + int level,
> + int max_level,
> + struct kvm_mmu_memory_cache *mc)
> +{
> + if (WARN_ON(level == max_level))
> + return 0;
> +
> + while (level++ < max_level) {
> + phys_addr_t rtt = alloc_delegated_page(realm, mc);
> +
> + if (rtt == PHYS_ADDR_MAX)
> + return -ENOMEM;
> +
> + if (realm_rtt_create(realm, ipa, level, rtt)) {
> + free_delegated_page(realm, rtt);
> + return -ENXIO;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int realm_tear_down_rtt_level(struct realm *realm, int level,
> unsigned long start, unsigned long end)
> {
> @@ -265,6 +440,68 @@ static int realm_tear_down_rtt_range(struct realm *realm,
> start, end);
> }
>
> +/*
> + * Returns 0 on successful fold, a negative value on error, a positive value if
> + * we were not able to fold all tables at this level.
> + */
> +static int realm_fold_rtt_level(struct realm *realm, int level,
> + unsigned long start, unsigned long end)
> +{
> + int not_folded = 0;
> + ssize_t map_size;
> + unsigned long addr, next_addr;
> +
> + if (WARN_ON(level > RME_RTT_MAX_LEVEL))
> + return -EINVAL;
> +
> + map_size = rme_rtt_level_mapsize(level - 1);
> +
> + for (addr = start; addr < end; addr = next_addr) {
> + phys_addr_t rtt_granule;
> + int ret;
> + unsigned long align_addr = ALIGN(addr, map_size);
> +
> + next_addr = ALIGN(addr + 1, map_size);
> +
> + ret = realm_rtt_fold(realm, align_addr, level, &rtt_granule);
> +
> + switch (RMI_RETURN_STATUS(ret)) {
> + case RMI_SUCCESS:
> + if (!WARN_ON(rmi_granule_undelegate(rtt_granule)))
> + free_page((unsigned long)phys_to_virt(rtt_granule));
> + break;
> + case RMI_ERROR_RTT:
> + if (level == RME_RTT_MAX_LEVEL ||
> + RMI_RETURN_INDEX(ret) < level) {
> + not_folded++;
> + break;
> + }
> + /* Recurse a level deeper */
> + ret = realm_fold_rtt_level(realm,
> + level + 1,
> + addr,
> + next_addr);
> + if (ret < 0)
> + return ret;
> + else if (ret == 0)
> + /* Try again at this level */
> + next_addr = addr;
> + break;
> + default:
> + return -ENXIO;
> + }
> + }
> +
> + return not_folded;
> +}
> +
> +static int realm_fold_rtt_range(struct realm *realm,
> + unsigned long start, unsigned long end)
> +{
> + return realm_fold_rtt_level(realm, get_start_level(realm) + 1,
> + start, end);
> +}
> +
> static void ensure_spare_page(struct realm *realm)
> {
> phys_addr_t tmp_rtt;
> @@ -295,6 +532,147 @@ void kvm_realm_destroy_rtts(struct kvm *kvm, u32 ia_bits)
> WARN_ON(realm_tear_down_rtt_range(realm, 0, (1UL << ia_bits)));
> }
>
> +void kvm_realm_unmap_range(struct kvm *kvm, unsigned long ipa, u64 size,
> + bool unmap_private)
> +{
> + unsigned long end = ipa + size;
> + struct realm *realm = &kvm->arch.realm;
> +
> + end = min(BIT(realm->ia_bits - 1), end);
> +
> + ensure_spare_page(realm);
> +
> + realm_unmap_range(kvm, ipa, end, unmap_private);
> +
> + realm_fold_rtt_range(realm, ipa, end);
> +}
> +
> +static int find_map_level(struct realm *realm,
> + unsigned long start,
> + unsigned long end)
> +{
> + int level = RME_RTT_MAX_LEVEL;
> +
> + while (level > get_start_level(realm)) {
> + unsigned long map_size = rme_rtt_level_mapsize(level - 1);
> +
> + if (!IS_ALIGNED(start, map_size) ||
> + (start + map_size) > end)
> + break;
> +
> + level--;
> + }
> +
> + return level;
> +}
> +
> +int realm_set_ipa_state(struct kvm_vcpu *vcpu,
> + unsigned long start,
> + unsigned long end,
> + unsigned long ripas)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + struct realm *realm = &kvm->arch.realm;
> + struct realm_rec *rec = &vcpu->arch.rec;
> + phys_addr_t rd_phys = virt_to_phys(realm->rd);
> + phys_addr_t rec_phys = virt_to_phys(rec->rec_page);
> + struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
> + unsigned long ipa = start;
> + int ret = 0;
> +
> + while (ipa < end) {
> + unsigned long next;
> +
> + ret = rmi_rtt_set_ripas(rd_phys, rec_phys, ipa, end, &next);
> +
> + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
> + int walk_level = RMI_RETURN_INDEX(ret);
> + int level = find_map_level(realm, ipa, end);
> +
> + if (walk_level < level) {
> + ret = realm_create_rtt_levels(realm, ipa,
> + walk_level,
> + level,
> + memcache);
> + if (!ret)
> + continue;
> + } else {
> + ret = -EINVAL;
> + }
> +
> + break;
> + } else if (RMI_RETURN_STATUS(ret) != RMI_SUCCESS) {
> + WARN(1, "Unexpected error in %s: %#x\n", __func__,
> + ret);
> + ret = -EINVAL;
> + break;
> + }
> + ipa = next;
> + }
> +
> + if (ripas == RMI_EMPTY && ipa != start)
> + kvm_realm_unmap_range(kvm, start, ipa - start, true);
> +
> + return ret;
> +}
> +
> +static int realm_init_ipa_state(struct realm *realm,
> + unsigned long ipa,
> + unsigned long end)
> +{
> + phys_addr_t rd_phys = virt_to_phys(realm->rd);
> + int ret;
> +
> + while (ipa < end) {
> + unsigned long next;
> +
> + ret = rmi_rtt_init_ripas(rd_phys, ipa, end, &next);
> +
> + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
> + int err_level = RMI_RETURN_INDEX(ret);
> + int level = find_map_level(realm, ipa, end);
> +
> + if (WARN_ON(err_level >= level))
> + return -ENXIO;
> +
> + ret = realm_create_rtt_levels(realm, ipa,
> + err_level,
> + level, NULL);
> + if (ret)
> + return ret;
> + /* Retry with the RTT levels in place */
> + continue;
> + } else if (WARN_ON(ret)) {
> + return -ENXIO;
> + }
> +
> + ipa = next;
> + }
> +
> + return 0;
> +}
> +
> +static int kvm_init_ipa_range_realm(struct kvm *kvm,
> + struct kvm_cap_arm_rme_init_ipa_args *args)
> +{
> + int ret = 0;
> + gpa_t addr, end;
> + struct realm *realm = &kvm->arch.realm;
> +
> + addr = args->init_ipa_base;
> + end = addr + args->init_ipa_size;
> +
> + if (end < addr)
> + return -EINVAL;
> +
> + if (kvm_realm_state(kvm) != REALM_STATE_NEW)
> + return -EINVAL;
> +
> + ret = realm_init_ipa_state(realm, addr, end);
> +
> + return ret;
> +}
> +
> /* Protects access to rme_vmid_bitmap */
> static DEFINE_SPINLOCK(rme_vmid_lock);
> static unsigned long *rme_vmid_bitmap;
> @@ -418,6 +796,18 @@ int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
> case KVM_CAP_ARM_RME_CREATE_RD:
> r = kvm_create_realm(kvm);
> break;
> + case KVM_CAP_ARM_RME_INIT_IPA_REALM: {
> + struct kvm_cap_arm_rme_init_ipa_args args;
> + void __user *argp = u64_to_user_ptr(cap->args[1]);
> +
> + if (copy_from_user(&args, argp, sizeof(args))) {
> + r = -EFAULT;
> + break;
> + }
> +
> + r = kvm_init_ipa_range_realm(kvm, &args);
> + break;
> + }
> default:
> r = -EINVAL;
> break;
> --
> 2.34.1
>