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KVM: arm64: Implement the MEM_UNSHARE hypercall for protected VMs

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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: Vincent Donnefort <vdonnefort@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260330144841.26181-31-will@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Will Deacon
2026-03-30 15:48:31 +01:00
committed by Marc Zyngier
parent 03313efed5
commit 246c976c37
3 changed files with 57 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
View File

@@ -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);

34
arch/arm64/kvm/hyp/nvhe/mem_protect.c
View File

@@ -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);

22
arch/arm64/kvm/hyp/nvhe/pkvm.c
View File

@@ -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;