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Message-ID: <CA+EHjTw48LTFt=sKtPwS1rmA=ma6Sj9O-D=17FXoMybqZ7+g5g@mail.gmail.com>
Date: Tue, 10 Dec 2024 14:41:12 +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 11/18] KVM: arm64: Introduce __pkvm_host_unshare_guest()
Hi Quentin,
On Tue, 3 Dec 2024 at 10:38, Quentin Perret <qperret@...gle.com> wrote:
>
> In preparation for letting the host unmap pages from non-protected
> guests, introduce a new hypercall implementing the host-unshare-guest
> transition.
>
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 1 +
> arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 +
> arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 5 ++
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 24 +++++++
> arch/arm64/kvm/hyp/nvhe/mem_protect.c | 67 +++++++++++++++++++
> 5 files changed, 98 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 449337f5b2a3..0b6c4d325134 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -66,6 +66,7 @@ enum __kvm_host_smccc_func {
> __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___pkvm_host_unshare_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/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> index a7976e50f556..e528a42ed60e 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> @@ -40,6 +40,7 @@ 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);
> +int __pkvm_host_unshare_guest(u64 gfn, struct pkvm_hyp_vm *hyp_vm);
The parameters of share_guest and unshare_guest are quite different. I
think that the unshare makes more sense, that it uses the hyp_vm as
opposed to the hyp_vcpu. Still, I think that one of the two should
change.
> 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/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> index be52c5b15e21..5dfc9ece9aa5 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
> @@ -64,6 +64,11 @@ static inline bool pkvm_hyp_vcpu_is_protected(struct pkvm_hyp_vcpu *hyp_vcpu)
> return vcpu_is_protected(&hyp_vcpu->vcpu);
> }
>
> +static inline bool pkvm_hyp_vm_is_protected(struct pkvm_hyp_vm *hyp_vm)
> +{
> + return kvm_vm_is_protected(&hyp_vm->kvm);
> +}
> +
> void pkvm_hyp_vm_table_init(void *tbl);
>
> int __pkvm_init_vm(struct kvm *host_kvm, unsigned long vm_hva,
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index d659462fbf5d..04a9053ae1d5 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -244,6 +244,29 @@ static void handle___pkvm_host_share_guest(struct kvm_cpu_context *host_ctxt)
> cpu_reg(host_ctxt, 1) = ret;
> }
>
> +static void handle___pkvm_host_unshare_guest(struct kvm_cpu_context *host_ctxt)
> +{
> + DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1);
> + DECLARE_REG(u64, gfn, host_ctxt, 2);
> + struct pkvm_hyp_vm *hyp_vm;
> + int ret = -EINVAL;
> +
> + if (!is_protected_kvm_enabled())
> + goto out;
> +
> + hyp_vm = get_pkvm_hyp_vm(handle);
> + if (!hyp_vm)
> + goto out;
> + if (pkvm_hyp_vm_is_protected(hyp_vm))
> + goto put_hyp_vm;
bikeshedding: is -EINVAL the best return value, or might -EPERM be
better if the VM is protected?
> +
> + ret = __pkvm_host_unshare_guest(gfn, hyp_vm);
> +put_hyp_vm:
> + put_pkvm_hyp_vm(hyp_vm);
> +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);
> @@ -454,6 +477,7 @@ 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(__pkvm_host_unshare_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 a69d7212b64c..aa27a3e42e5e 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -1413,3 +1413,70 @@ int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
>
> return ret;
> }
> +
> +static int __check_host_unshare_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ipa)
nit: sometimes (in this and other patches) you use vm to refer to
pkvm_hyp_vm, and other times you use hyp_vm. Makes grepping/searching
a bit more tricky.
Cheers,
/fuad
> +{
> + enum pkvm_page_state state;
> + struct hyp_page *page;
> + kvm_pte_t pte;
> + u64 phys;
> + s8 level;
> + int ret;
> +
> + ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level);
> + if (ret)
> + return ret;
> + if (level != KVM_PGTABLE_LAST_LEVEL)
> + return -E2BIG;
> + if (!kvm_pte_valid(pte))
> + return -ENOENT;
> +
> + state = guest_get_page_state(pte, ipa);
> + if (state != PKVM_PAGE_SHARED_BORROWED)
> + return -EPERM;
> +
> + phys = kvm_pte_to_phys(pte);
> + ret = range_is_allowed_memory(phys, phys + PAGE_SIZE);
> + if (WARN_ON(ret))
> + return ret;
> +
> + page = hyp_phys_to_page(phys);
> + if (page->host_state != PKVM_PAGE_SHARED_OWNED)
> + return -EPERM;
> + if (WARN_ON(!page->host_share_guest_count))
> + return -EINVAL;
> +
> + *__phys = phys;
> +
> + return 0;
> +}
> +
> +int __pkvm_host_unshare_guest(u64 gfn, struct pkvm_hyp_vm *hyp_vm)
> +{
> + u64 ipa = hyp_pfn_to_phys(gfn);
> + struct hyp_page *page;
> + u64 phys;
> + int ret;
> +
> + host_lock_component();
> + guest_lock_component(hyp_vm);
> +
> + ret = __check_host_unshare_guest(hyp_vm, &phys, ipa);
> + if (ret)
> + goto unlock;
> +
> + ret = kvm_pgtable_stage2_unmap(&hyp_vm->pgt, ipa, PAGE_SIZE);
> + if (ret)
> + goto unlock;
> +
> + page = hyp_phys_to_page(phys);
> + page->host_share_guest_count--;
> + if (!page->host_share_guest_count)
> + WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_OWNED));
> +
> +unlock:
> + guest_unlock_component(hyp_vm);
> + host_unlock_component();
> +
> + return ret;
> +}
> --
> 2.47.0.338.g60cca15819-goog
>
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