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KVM: arm64: Implement the MEM_SHARE hypercall for protected VMs

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Implement the ARM_SMCCC_KVM_FUNC_MEM_SHARE hypercall to allow protected
VMs to share memory (e.g. the swiotlb bounce buffers) back to the host.

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/20260330144841.26181-30-will@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Will Deacon 2026-03-30 15:48:30 +01:00 committed by Marc Zyngier
parent 94c5250515
commit 03313efed5
3 changed files with 94 additions and 0 deletions
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1
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
View File

@ -34,6 +34,7 @@ extern unsigned long hyp_nr_cpus;
int __pkvm_prot_finalize(void); int __pkvm_prot_finalize(void);
int __pkvm_host_share_hyp(u64 pfn); int __pkvm_host_share_hyp(u64 pfn);
int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn);
int __pkvm_host_unshare_hyp(u64 pfn); int __pkvm_host_unshare_hyp(u64 pfn);
int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages); int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages);
int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages); int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages);

32
arch/arm64/kvm/hyp/nvhe/mem_protect.c
View File

@ -959,6 +959,38 @@ int __pkvm_host_share_hyp(u64 pfn)
return ret; return ret;
} }
int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn)
{
struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
u64 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_OWNED)
goto unlock;
if (__host_check_page_state_range(phys, PAGE_SIZE, PKVM_NOPAGE))
goto unlock;
ret = 0;
WARN_ON(kvm_pgtable_stage2_map(&vm->pgt, ipa, PAGE_SIZE, phys,
pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED),
&vcpu->vcpu.arch.pkvm_memcache, 0));
WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED));
unlock:
guest_unlock_component(vm);
host_unlock_component();
return ret;
}
int __pkvm_host_unshare_hyp(u64 pfn) int __pkvm_host_unshare_hyp(u64 pfn)
{ {
u64 phys = hyp_pfn_to_phys(pfn); u64 phys = hyp_pfn_to_phys(pfn);

61
arch/arm64/kvm/hyp/nvhe/pkvm.c
View File

@ -973,6 +973,58 @@ int __pkvm_finalize_teardown_vm(pkvm_handle_t handle)
hyp_spin_unlock(&vm_table_lock); hyp_spin_unlock(&vm_table_lock);
return err; return err;
} }
static u64 __pkvm_memshare_page_req(struct kvm_vcpu *vcpu, u64 ipa)
{
u64 elr;
/* Fake up a data abort (level 3 translation fault on write) */
vcpu->arch.fault.esr_el2 = (ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT) |
ESR_ELx_WNR | ESR_ELx_FSC_FAULT |
FIELD_PREP(ESR_ELx_FSC_LEVEL, 3);
/* Shuffle the IPA around into the HPFAR */
vcpu->arch.fault.hpfar_el2 = (HPFAR_EL2_NS | (ipa >> 8)) & HPFAR_MASK;
/* This is a virtual address. 0's good. Let's go with 0. */
vcpu->arch.fault.far_el2 = 0;
/* Rewind the ELR so we return to the HVC once the IPA is mapped */
elr = read_sysreg(elr_el2);
elr -= 4;
write_sysreg(elr, elr_el2);
return ARM_EXCEPTION_TRAP;
}
static bool pkvm_memshare_call(u64 *ret, struct kvm_vcpu *vcpu, u64 *exit_code)
{
struct pkvm_hyp_vcpu *hyp_vcpu;
u64 ipa = smccc_get_arg1(vcpu);
if (!PAGE_ALIGNED(ipa))
goto out_guest;
hyp_vcpu = container_of(vcpu, struct pkvm_hyp_vcpu, vcpu);
switch (__pkvm_guest_share_host(hyp_vcpu, hyp_phys_to_pfn(ipa))) {
case 0:
ret[0] = SMCCC_RET_SUCCESS;
goto out_guest;
case -ENOENT:
/*
* Convert the exception into a data abort so that the page
* being shared is mapped into the guest next time.
*/
*exit_code = __pkvm_memshare_page_req(vcpu, ipa);
goto out_host;
}
out_guest:
return true;
out_host:
return false;
}
/* /*
* Handler for protected VM HVC calls. * Handler for protected VM HVC calls.
* *
@ -989,6 +1041,7 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code)
case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID: case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES); val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
val[0] |= BIT(ARM_SMCCC_KVM_FUNC_HYP_MEMINFO); val[0] |= BIT(ARM_SMCCC_KVM_FUNC_HYP_MEMINFO);
val[0] |= BIT(ARM_SMCCC_KVM_FUNC_MEM_SHARE);
break; break;
case ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID: case ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID:
if (smccc_get_arg1(vcpu) || if (smccc_get_arg1(vcpu) ||
@ -999,6 +1052,14 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code)
val[0] = PAGE_SIZE; val[0] = PAGE_SIZE;
break; break;
case ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID:
if (smccc_get_arg2(vcpu) ||
smccc_get_arg3(vcpu)) {
break;
}
handled = pkvm_memshare_call(val, vcpu, exit_code);
break;
default: default:
/* Punt everything else back to the host, for now. */ /* Punt everything else back to the host, for now. */
handled = false; handled = false;