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[35.189.235.63]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fec232d74sm181843f8f.17.2026.08.04.07.50.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2026 07:50:14 -0700 (PDT) Date: Tue, 4 Aug 2026 14:50:10 +0000 From: Sebastian Ene To: Vincent Donnefort Cc: alexandru.elisei@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com, catalin.marinas@arm.com, dbrazdil@google.com, joey.gouly@arm.com, kees@kernel.org, mark.rutland@arm.com, maz@kernel.org, oupton@kernel.org, perlarsen@google.com, qperret@google.com, rananta@google.com, smostafa@google.com, suzuki.poulose@arm.com, tabba@google.com, tglx@kernel.org, bgrzesik@google.com, will@kernel.org, yuzenghui@huawei.com Subject: Re: [PATCH 02/14] KVM: arm64: Track host-unmapped MMIO regions in a static array Message-ID: References: <20260310124933.830025-1-sebastianene@google.com> <20260310124933.830025-3-sebastianene@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260804_075018_448706_FC196252 X-CRM114-Status: GOOD ( 29.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 24, 2026 at 10:46:45AM +0000, Vincent Donnefort wrote: > On Tue, Mar 10, 2026 at 12:49:21PM +0000, Sebastian Ene wrote: > > Introduce a registry to track protected MMIO regions that are unmapped > > from the host stage-2 page tables. These regions are stored in a > > fixed-size array and their ownership is donated to the hypervisor during > > initialization to ensure host-exclusion and persistent tracking. > > > > Signed-off-by: Sebastian Ene > > --- > > arch/arm64/include/asm/kvm_pkvm.h | 10 ++++++++++ > > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +++ > > arch/arm64/kvm/hyp/nvhe/setup.c | 25 +++++++++++++++++++++++++ > > 3 files changed, 38 insertions(+) > > > > diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h > > index 757076ad4ec9..48ec7d519399 100644 > > --- a/arch/arm64/include/asm/kvm_pkvm.h > > +++ b/arch/arm64/include/asm/kvm_pkvm.h > > @@ -17,6 +17,16 @@ > > > > #define HYP_MEMBLOCK_REGIONS 128 > > > > +#define PKVM_PROTECTED_REGS_NUM 8 > > + > > +struct pkvm_protected_reg { > > + u64 start_pfn; > > + size_t num_pages; > > nit: "u64 pfn, u64 nr_pages" to align with everywhere else. Ack, > > > +}; > > + > > +extern struct pkvm_protected_reg kvm_nvhe_sym(pkvm_protected_regs)[]; > > +extern unsigned int kvm_nvhe_sym(num_protected_reg); > > + > > int pkvm_init_host_vm(struct kvm *kvm); > > int pkvm_create_hyp_vm(struct kvm *kvm); > > bool pkvm_hyp_vm_is_created(struct kvm *kvm); > > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > index 0808367c52e5..7c125836b533 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > > @@ -23,6 +23,9 @@ > > > > struct host_mmu host_mmu; > > > > +struct pkvm_protected_reg pkvm_protected_regs[PKVM_PROTECTED_REGS_NUM]; > > +unsigned int num_protected_reg; > > + > > static struct hyp_pool host_s2_pool; > > > > static DEFINE_PER_CPU(struct pkvm_hyp_vm *, __current_vm); > > diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c > > index 90bd014e952f..ad5b96085e1b 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/setup.c > > +++ b/arch/arm64/kvm/hyp/nvhe/setup.c > > @@ -284,6 +284,27 @@ static int fix_hyp_pgtable_refcnt(void) > > &walker); > > } > > > > +static int unmap_protected_regions(void) > > +{ > > + struct pkvm_protected_reg *reg; > > + int i, ret, j = 0; > > + > > + for (i = 0; i < num_protected_reg; i++) { > > + reg = &pkvm_protected_regs[i]; > > + for (j = 0; j < reg->num_pages; j++) { > > + ret = __pkvm_host_donate_hyp_mmio(reg->start_pfn + j); > > If this is to make this static at boot, we don't even need __pkvm_host_donate_hyp_mmio() > > We can just map the region early enough in the hypervisor pkvm_create_mappings() > in recreate_hyp_mappings() and then let fix_host_ownership() do the host > stage2 unmapping. I looked at this and tried to implement it this way as you suggest because it is more elegant but then I realized that `fix_host_ownership_walker` doesn't do well with MMIO (it returns -EINVAL). > > > + if (ret) > > + goto err_setup; > > + } > > + } > > + > > + return 0; > > +err_setup: > > + for (j = j - 1; j >= 0; j--) > > + __pkvm_hyp_donate_host_mmio(reg->start_pfn + j); > > + return ret; > > +} > > + > > void __noreturn __pkvm_init_finalise(void) > > { > > struct kvm_cpu_context *host_ctxt = host_data_ptr(host_ctxt); > > @@ -324,6 +345,10 @@ void __noreturn __pkvm_init_finalise(void) > > if (ret) > > goto out; > > > > + ret = unmap_protected_regions(); > > + if (ret) > > + goto out; > > + > > ret = hyp_ffa_init(ffa_proxy_pages); > > if (ret) > > goto out; > > -- > > 2.53.0.473.g4a7958ca14-goog > > Thanks Sebastian