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[34.77.69.137]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493eb6f3dcdsm143760685e9.3.2026.07.10.09.17.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 09:17:36 -0700 (PDT) Date: Fri, 10 Jul 2026 17:17:32 +0100 From: Vincent Donnefort To: Mostafa Saleh Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, iommu@lists.linux.dev, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, joro@8bytes.org, jean-philippe@linaro.org, jgg@ziepe.ca, mark.rutland@arm.com, qperret@google.com, tabba@google.com, sebastianene@google.com, keirf@google.com Subject: Re: [PATCH v6 07/25] KVM: arm64: iommu: Introduce IOMMU driver infrastructure Message-ID: References: <20260501111928.259252-1-smostafa@google.com> <20260501111928.259252-8-smostafa@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260501111928.259252-8-smostafa@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260710_091740_526677_4E6ADF05 X-CRM114-Status: GOOD ( 31.61 ) 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 Fri, May 01, 2026 at 11:19:09AM +0000, Mostafa Saleh wrote: > To establish DMA isolation, KVM needs an IOMMU driver which provides > ops implemented at EL2. > > Only one driver can be used and is registered with > kvm_iommu_register_driver() by passing pointer to the ops. > > This must be called before module_init() which is the point KVM > initializes. Everywhere s/KVM/pKVM/ as this can be registered only if pKVM is enabled. > > Signed-off-by: Jean-Philippe Brucker > Signed-off-by: Mostafa Saleh > --- > arch/arm64/include/asm/kvm_host.h | 5 +++++ > arch/arm64/kvm/Makefile | 2 +- > arch/arm64/kvm/hyp/include/nvhe/iommu.h | 13 +++++++++++++ > arch/arm64/kvm/hyp/nvhe/Makefile | 3 ++- > arch/arm64/kvm/hyp/nvhe/iommu/iommu.c | 20 +++++++++++++++++++ > arch/arm64/kvm/hyp/nvhe/setup.c | 5 +++++ > arch/arm64/kvm/iommu.c | 26 +++++++++++++++++++++++++ > 7 files changed, 72 insertions(+), 2 deletions(-) > create mode 100644 arch/arm64/kvm/hyp/include/nvhe/iommu.h > create mode 100644 arch/arm64/kvm/hyp/nvhe/iommu/iommu.c > create mode 100644 arch/arm64/kvm/iommu.c > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 851f6171751c..52898d2a3ec6 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -1733,4 +1733,9 @@ static __always_inline enum fgt_group_id __fgt_reg_to_group_id(enum vcpu_sysreg > > long kvm_get_cap_for_kvm_ioctl(unsigned int ioctl, long *ext); > > +#ifndef __KVM_NVHE_HYPERVISOR__ I think it's not necessary, a lot of things aren't guarded for __KVM_NVHE_HYPERVISOR__. > +struct kvm_iommu_ops; Perhaps we can keep this private to hyp code by just using (void *) here? > +int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops); > +#endif > + > #endif /* __ARM64_KVM_HOST_H__ */ > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > index 59612d2f277c..0ddef54f7434 100644 > --- a/arch/arm64/kvm/Makefile > +++ b/arch/arm64/kvm/Makefile > @@ -24,7 +24,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \ > vgic/vgic-mmio.o vgic/vgic-mmio-v2.o \ > vgic/vgic-mmio-v3.o vgic/vgic-kvm-device.o \ > vgic/vgic-its.o vgic/vgic-debug.o vgic/vgic-v3-nested.o \ > - vgic/vgic-v5.o > + vgic/vgic-v5.o iommu.o alphabetical order. > > kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o > kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o > diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h > new file mode 100644 > index 000000000000..1ac70cc28a9e > --- /dev/null > +++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h > @@ -0,0 +1,13 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ARM64_KVM_NVHE_IOMMU_H__ > +#define __ARM64_KVM_NVHE_IOMMU_H__ > + > +#include > + > +struct kvm_iommu_ops { > + int (*init)(void); > +}; > + > +int kvm_iommu_init(void); > + > +#endif /* __ARM64_KVM_NVHE_IOMMU_H__ */ > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile > index 89d0533921f9..606c0e1b7bd0 100644 > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > @@ -24,7 +24,8 @@ CFLAGS_switch.nvhe.o += -Wno-override-init > > hyp-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \ > hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \ > - cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o ffa.o > + cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o ffa.o \ > + iommu/iommu.o > hyp-obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \ > ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o ../vgic-v5-sr.o clock.o > hyp-obj-y += ../../../kernel/smccc-call.o > diff --git a/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c > new file mode 100644 > index 000000000000..406c8fb9b3b9 > --- /dev/null > +++ b/arch/arm64/kvm/hyp/nvhe/iommu/iommu.c > @@ -0,0 +1,20 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * IOMMU operations for pKVM > + * > + * Copyright (C) 2022 Linaro Ltd. > + */ > +#include > + > +/* Only one set of ops supported */ > +struct kvm_iommu_ops *kvm_iommu_ops; > + > + Empty line. > +int kvm_iommu_init(void) > +{ > + /* Keep DMA isolation optional. */ > + if (!kvm_iommu_ops || !kvm_iommu_ops->init) > + return 0; The absence of the SME workaround on affected systems breaks pKVM init. So perhaps the IOMMU should do the same? (see pkvm_check_sme_dvmsync_fw_call()) > + > + return kvm_iommu_ops->init(); > +} > diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c > index 8041f6e80cd1..1f6b221db9a0 100644 > --- a/arch/arm64/kvm/hyp/nvhe/setup.c > +++ b/arch/arm64/kvm/hyp/nvhe/setup.c > @@ -14,6 +14,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -329,6 +330,10 @@ void __noreturn __pkvm_init_finalise(void) > if (ret) > goto out; > > + ret = kvm_iommu_init(); > + if (ret) > + goto out; > + > ret = hyp_ffa_init(ffa_proxy_pages); > if (ret) > goto out; > diff --git a/arch/arm64/kvm/iommu.c b/arch/arm64/kvm/iommu.c > new file mode 100644 > index 000000000000..f247384fa193 > --- /dev/null > +++ b/arch/arm64/kvm/iommu.c > @@ -0,0 +1,26 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2025 Google LLC > + * Author: Mostafa Saleh > + */ > + > +#include > + > +extern struct kvm_iommu_ops *kvm_nvhe_sym(kvm_iommu_ops); > + > +static DEFINE_MUTEX(kvm_iommu_reg_lock); could be moved directly into the only user: kvm_iommu_register_driver > + > +int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops) __init ? > +{ > + guard(mutex)(&kvm_iommu_reg_lock); > + > + /* Only protected KVM before de-privilege. */ Don't think that comment brings much information, looking at the line below. > + if (!is_protected_kvm_enabled() || is_kvm_arm_initialised()) > + return -EINVAL; -EPERM? > + > + if (kvm_nvhe_sym(kvm_iommu_ops)) > + return -EBUSY; > + > + kvm_nvhe_sym(kvm_iommu_ops) = hyp_ops; > + return 0; > +} > -- > 2.54.0.545.g6539524ca2-goog >