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[34.34.145.44]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d7f41f5e0sm49020395e9.8.2026.01.06.07.50.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Jan 2026 07:50:10 -0800 (PST) Date: Tue, 6 Jan 2026 15:50:07 +0000 From: Vincent Donnefort To: Will Deacon Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Quentin Perret , Fuad Tabba , Mostafa Saleh Subject: Re: [PATCH 25/30] KVM: arm64: Implement the MEM_UNSHARE hypercall for protected VMs Message-ID: References: <20260105154939.11041-1-will@kernel.org> <20260105154939.11041-26-will@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260105154939.11041-26-will@kernel.org> On Mon, Jan 05, 2026 at 03:49:33PM +0000, Will Deacon wrote: > 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. > > Signed-off-by: Will Deacon Reviewed-by: Vincent Donnefort > --- > arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 32 +++++++++++++++++++ > arch/arm64/kvm/hyp/nvhe/pkvm.c | 22 +++++++++++++ > 3 files changed, 55 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > index 42fd60c5cfc9..e41a128b0854 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > @@ -36,6 +36,7 @@ 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); > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > index 365c769c82a4..c1600b88c316 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -920,6 +920,38 @@ 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 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; > + WARN_ON(host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_GUEST)); > + 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); > diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c > index d8afa2b98542..2890328f4a78 100644 > --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c > +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c > @@ -988,6 +988,19 @@ 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. > * > @@ -1005,6 +1018,7 @@ 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) || > @@ -1023,6 +1037,14 @@ 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; > -- > 2.52.0.351.gbe84eed79e-goog >