Commit 246c976c authored by Will Deacon's avatar Will Deacon Committed by Marc Zyngier
Browse files

KVM: arm64: Implement the MEM_UNSHARE hypercall for protected VMs 



Implement the ARM_SMCCC_KVM_FUNC_MEM_UNSHARE hypercall to allow
protected VMs to unshare memory that was previously shared with the host
using the ARM_SMCCC_KVM_FUNC_MEM_SHARE hypercall.

Reviewed-by: default avatarVincent Donnefort <vdonnefort@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Tested-by: default avatarMostafa Saleh <smostafa@google.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260330144841.26181-31-will@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 03313efe

arch/arm64/kvm/hyp/include/nvhe/mem_protect.h

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ extern unsigned long hyp_nr_cpus; 
int __pkvm_prot_finalize(void);

int __pkvm_host_share_hyp(u64 pfn);

int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn);

int __pkvm_guest_unshare_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn);

int __pkvm_host_unshare_hyp(u64 pfn);

int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);

int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);

arch/arm64/kvm/hyp/nvhe/mem_protect.c

+34 −0
Original line number Diff line number Diff line
@@ -991,6 +991,40 @@ int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn) 
	return ret;

}



int __pkvm_guest_unshare_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn)

{

	struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);

	u64 meta, phys, ipa = hyp_pfn_to_phys(gfn);

	kvm_pte_t pte;

	int ret;



	host_lock_component();

	guest_lock_component(vm);



	ret = get_valid_guest_pte(vm, ipa, &pte, &phys);

	if (ret)

		goto unlock;



	ret = -EPERM;

	if (pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte)) != PKVM_PAGE_SHARED_OWNED)

		goto unlock;

	if (__host_check_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED))

		goto unlock;



	ret = 0;

	meta = host_stage2_encode_gfn_meta(vm, gfn);

	WARN_ON(host_stage2_set_owner_metadata_locked(phys, PAGE_SIZE,

						      PKVM_ID_GUEST, meta));

	WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys,

				       pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_OWNED),

				       &vcpu->vcpu.arch.pkvm_memcache, 0));

unlock:

	guest_unlock_component(vm);

	host_unlock_component();



	return ret;

}



int __pkvm_host_unshare_hyp(u64 pfn)

{

	u64 phys = hyp_pfn_to_phys(pfn);

arch/arm64/kvm/hyp/nvhe/pkvm.c

+22 −0
Original line number Diff line number Diff line
@@ -1025,6 +1025,19 @@ static bool pkvm_memshare_call(u64 *ret, struct kvm_vcpu *vcpu, u64 *exit_code) 
	return false;

}



static void pkvm_memunshare_call(u64 *ret, struct kvm_vcpu *vcpu)

{

	struct pkvm_hyp_vcpu *hyp_vcpu;

	u64 ipa = smccc_get_arg1(vcpu);



	if (!PAGE_ALIGNED(ipa))

		return;



	hyp_vcpu = container_of(vcpu, struct pkvm_hyp_vcpu, vcpu);

	if (!__pkvm_guest_unshare_host(hyp_vcpu, hyp_phys_to_pfn(ipa)))

		ret[0] = SMCCC_RET_SUCCESS;

}



/*

 * Handler for protected VM HVC calls.

 *
@@ -1042,6 +1055,7 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) 
		val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);

		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_HYP_MEMINFO);

		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MEM_SHARE);

		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MEM_UNSHARE);

		break;

	case ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID:

		if (smccc_get_arg1(vcpu) ||
@@ -1060,6 +1074,14 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code) 


		handled = pkvm_memshare_call(val, vcpu, exit_code);

		break;

	case ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID:

		if (smccc_get_arg2(vcpu) ||

		    smccc_get_arg3(vcpu)) {

			break;

		}



		pkvm_memunshare_call(val, vcpu);

		break;

	default:

		/* Punt everything else back to the host, for now. */

		handled = false;