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Message-ID: <CA+EHjTwHSyQ1FJc7axbLNuBxSWpRVE6brb34nO+F59=QRmfQEg@mail.gmail.com>
Date: Tue, 10 Dec 2024 13:58:42 +0000
From: Fuad Tabba <tabba@...gle.com>
To: Quentin Perret <qperret@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>, Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Vincent Donnefort <vdonnefort@...gle.com>,
Sebastian Ene <sebastianene@...gle.com>, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/18] KVM: arm64: Introduce __pkvm_host_share_guest()
Hi Quentin,
On Tue, 3 Dec 2024 at 10:37, Quentin Perret <qperret@...gle.com> wrote:
>
> In preparation for handling guest stage-2 mappings at EL2, introduce a
> new pKVM hypercall allowing to share pages with non-protected guests.
>
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 1 +
> arch/arm64/include/asm/kvm_host.h | 3 +
> arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 +
> arch/arm64/kvm/hyp/include/nvhe/memory.h | 2 +
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 34 +++++++++
> arch/arm64/kvm/hyp/nvhe/mem_protect.c | 70 +++++++++++++++++++
> arch/arm64/kvm/hyp/nvhe/pkvm.c | 7 ++
> 7 files changed, 118 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 89c0fac69551..449337f5b2a3 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -65,6 +65,7 @@ enum __kvm_host_smccc_func {
> /* Hypercalls available after pKVM finalisation */
> __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
> __KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
> + __KVM_HOST_SMCCC_FUNC___pkvm_host_share_guest,
> __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
> __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
> __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index e18e9244d17a..f75988e3515b 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -771,6 +771,9 @@ struct kvm_vcpu_arch {
> /* Cache some mmu pages needed inside spinlock regions */
> struct kvm_mmu_memory_cache mmu_page_cache;
>
> + /* Pages to be donated to pkvm/EL2 if it runs out */
Runs out of what? :) I'm being facetious, it's just that the comment
is a bit unclear.
> + struct kvm_hyp_memcache pkvm_memcache;
> +
> /* Virtual SError ESR to restore when HCR_EL2.VSE is set */
> u64 vsesr_el2;
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> index 25038ac705d8..a7976e50f556 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> @@ -39,6 +39,7 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
> int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);
> int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages);
> int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
> +int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_pgtable_prot prot);
>
> bool addr_is_memory(phys_addr_t phys);
> int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> index 08f3a0416d4c..457318215155 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> @@ -47,6 +47,8 @@ struct hyp_page {
>
> /* Host (non-meta) state. Guarded by the host stage-2 lock. */
> enum pkvm_page_state host_state : 8;
> +
> + u32 host_share_guest_count;
> };
>
> extern u64 __hyp_vmemmap;
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 95d78db315b3..d659462fbf5d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -211,6 +211,39 @@ static void handle___kvm_vcpu_run(struct kvm_cpu_context *host_ctxt)
> cpu_reg(host_ctxt, 1) = ret;
> }
>
> +static int pkvm_refill_memcache(struct pkvm_hyp_vcpu *hyp_vcpu)
> +{
> + struct kvm_vcpu *host_vcpu = hyp_vcpu->host_vcpu;
> +
> + return refill_memcache(&hyp_vcpu->vcpu.arch.pkvm_memcache,
> + host_vcpu->arch.pkvm_memcache.nr_pages,
> + &host_vcpu->arch.pkvm_memcache);
> +}
> +
> +static void handle___pkvm_host_share_guest(struct kvm_cpu_context *host_ctxt)
> +{
> + DECLARE_REG(u64, pfn, host_ctxt, 1);
> + DECLARE_REG(u64, gfn, host_ctxt, 2);
> + DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 3);
> + struct pkvm_hyp_vcpu *hyp_vcpu;
> + int ret = -EINVAL;
> +
> + if (!is_protected_kvm_enabled())
> + goto out;
> +
> + hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
> + if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu))
> + goto out;
> +
> + ret = pkvm_refill_memcache(hyp_vcpu);
> + if (ret)
> + goto out;
> +
> + ret = __pkvm_host_share_guest(pfn, gfn, hyp_vcpu, prot);
> +out:
> + cpu_reg(host_ctxt, 1) = ret;
> +}
> +
> static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt)
> {
> DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
> @@ -420,6 +453,7 @@ static const hcall_t host_hcall[] = {
>
> HANDLE_FUNC(__pkvm_host_share_hyp),
> HANDLE_FUNC(__pkvm_host_unshare_hyp),
> + HANDLE_FUNC(__pkvm_host_share_guest),
> HANDLE_FUNC(__kvm_adjust_pc),
> HANDLE_FUNC(__kvm_vcpu_run),
> HANDLE_FUNC(__kvm_flush_vm_context),
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 1595081c4f6b..a69d7212b64c 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -861,6 +861,27 @@ static int hyp_complete_donation(u64 addr,
> return pkvm_create_mappings_locked(start, end, prot);
> }
>
> +static enum pkvm_page_state guest_get_page_state(kvm_pte_t pte, u64 addr)
> +{
> + if (!kvm_pte_valid(pte))
> + return PKVM_NOPAGE;
> +
> + return pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte));
> +}
> +
> +static int __guest_check_page_state_range(struct pkvm_hyp_vcpu *vcpu, u64 addr,
> + u64 size, enum pkvm_page_state state)
> +{
> + struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
> + struct check_walk_data d = {
> + .desired = state,
> + .get_page_state = guest_get_page_state,
> + };
> +
> + hyp_assert_lock_held(&vm->lock);
> + return check_page_state_range(&vm->pgt, addr, size, &d);
> +}
> +
> static int check_share(struct pkvm_mem_share *share)
> {
> const struct pkvm_mem_transition *tx = &share->tx;
> @@ -1343,3 +1364,52 @@ int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages)
>
> return ret;
> }
> +
> +int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
> + enum kvm_pgtable_prot prot)
> +{
> + struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
> + u64 phys = hyp_pfn_to_phys(pfn);
> + u64 ipa = hyp_pfn_to_phys(gfn);
> + struct hyp_page *page;
> + int ret;
> +
> + if (prot & ~KVM_PGTABLE_PROT_RWX)
> + return -EINVAL;
> +
> + ret = range_is_allowed_memory(phys, phys + PAGE_SIZE);
> + if (ret)
> + return ret;
> +
> + host_lock_component();
> + guest_lock_component(vm);
> +
> + ret = __guest_check_page_state_range(vcpu, ipa, PAGE_SIZE, PKVM_NOPAGE);
> + if (ret)
> + goto unlock;
> +
> + page = hyp_phys_to_page(phys);
> + switch (page->host_state) {
> + case PKVM_PAGE_OWNED:
> + WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_OWNED));
> + break;
> + case PKVM_PAGE_SHARED_OWNED:
> + /* Only host to np-guest multi-sharing is tolerated */
Initially I thought the comment was related to the warning below,
which confused me. Now I think what you're trying to say is that we'll
allow the share, and the (unrelated to the comment) warning is to
ensure that the PKVM_PAGE_SHARED_OWNED is consistent with the share
count.
I think what you should have here, which would work better with the
comment, is something like:
/* Only host to np-guest multi-sharing is tolerated */
+ if (pkvm_hyp_vcpu_is_protected(vcpu))
+ return -EPERM;
That would even make the comment unnecessary.
> + WARN_ON(!page->host_share_guest_count);
> + break;
> + default:
> + ret = -EPERM;
> + goto unlock;
> + }
> +
> + WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys,
> + pkvm_mkstate(prot, PKVM_PAGE_SHARED_BORROWED),
> + &vcpu->vcpu.arch.pkvm_memcache, 0));
> + page->host_share_guest_count++;
> +
> +unlock:
> + guest_unlock_component(vm);
> + host_unlock_component();
> +
> + return ret;
> +}
> diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> index d5c23449a64c..d6c61a5e7b6e 100644
> --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
> +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> @@ -795,6 +795,13 @@ int __pkvm_teardown_vm(pkvm_handle_t handle)
> /* Push the metadata pages to the teardown memcache */
> for (idx = 0; idx < hyp_vm->nr_vcpus; ++idx) {
> struct pkvm_hyp_vcpu *hyp_vcpu = hyp_vm->vcpus[idx];
> + struct kvm_hyp_memcache *vcpu_mc = &hyp_vcpu->vcpu.arch.pkvm_memcache;
> +
> + while (vcpu_mc->nr_pages) {
> + void *addr = pop_hyp_memcache(vcpu_mc, hyp_phys_to_virt);
nit: newline
Cheers,
/fuad
> + push_hyp_memcache(mc, addr, hyp_virt_to_phys);
> + unmap_donated_memory_noclear(addr, PAGE_SIZE);
> + }
>
> teardown_donated_memory(mc, hyp_vcpu, sizeof(*hyp_vcpu));
> }
> --
> 2.47.0.338.g60cca15819-goog
>
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