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[34.76.60.220]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47aa039ae44sm80270824f8f.23.2026.07.13.03.13.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2026 03:13:15 -0700 (PDT) Date: Mon, 13 Jul 2026 10:13:09 +0000 From: Mostafa Saleh To: Vincent Donnefort 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jul 10, 2026 at 05:17:32PM +0100, Vincent Donnefort wrote: > 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. Will do. > > > > > 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__. That makes it clear that it is hypervisor code, but no strong opinion. > > > +struct kvm_iommu_ops; > > Perhaps we can keep this private to hyp code by just using (void *) here? That does not leak the struct, it is just a forward declaration, I beleive it is more clear and readable this way. > > > +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. That does not seem to be already sorted. > > > > > 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. > Will remove it. > > +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()) > I initially done something similar, but I was not sure if that is too limiting as now pKVM will not run on many hardware, I think the best option is to make this cmdline configurable wether DMA isolation is required or not. But for this series we can keep it optional. > > + > > + 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 No strong opinion, it seemed it can be easily re-used this way. > > > + > > +int kvm_iommu_register_driver(struct kvm_iommu_ops *hyp_ops) > > __init ? Will do. > > > +{ > > + 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. I will remove it. > > > + if (!is_protected_kvm_enabled() || is_kvm_arm_initialised()) > > + return -EINVAL; > > -EPERM? I can see it both ways, my thought that it is invalid to register a driver after a certain point, but -EPERM makes sense also. Thanks, Mostafa