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Thu, 15 Oct 2026 13:09:21 -0700 (PDT) Date: Thu, 15 Oct 2026 20:08:40 +0000 In-Reply-To: <20261015200903.2735565-1-smostafa@google.com> Mime-Version: 1.0 References: <20261015200903.2735565-1-smostafa@google.com> X-Mailer: git-send-email 2.56.0.176.g3575e65682-goog Message-ID: <20261015200903.2735565-10-smostafa@google.com> Subject: [PATCH v9 09/25] KVM: arm64: iommu: Support DABT for IOMMU From: Mostafa Saleh To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, iommu@lists.linux.dev Cc: 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, jgg@ziepe.ca, mark.rutland@arm.com, qperret@google.com, tabba@google.com, vdonnefort@google.com, nicolinc@nvidia.com, Mostafa Saleh Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261015_130924_412599_366C8B83 X-CRM114-Status: GOOD ( 17.47 ) 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 The pKVM SMMUv3 driver emulates the SMMU registers for the host: the MMIO is donated to the hypervisor so that host accesses trap, and the hypervisor performs or rejects each access on the host's behalf. Add a dabt_handler op and call it from the host data abort path for aborts with a valid instruction syndrome on non-memory addresses. If the driver emulates the access, skip the faulting instruction, otherwise take the normal path, where hyp-owned MMIO is denied. Only aborts with a valid instruction syndrome can be emulated, so the host must access emulated registers with single-register loads and stores (readl/writel and friends). Signed-off-by: Mostafa Saleh --- arch/arm64/kvm/hyp/include/nvhe/iommu.h | 9 +++++++++ arch/arm64/kvm/hyp/nvhe/iommu.c | 6 ++++++ arch/arm64/kvm/hyp/nvhe/mem_protect.c | 17 +++++++++++++++++ 3 files changed, 32 insertions(+) diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h index acd5058ef3ed..bd6604f194b5 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/iommu.h +++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h @@ -13,6 +13,13 @@ struct pkvm_iommu_ops { * with the same @prot, which must succeed. */ int (*host_stage2_idmap)(phys_addr_t start, phys_addr_t end, int prot); + /* + * Emulate a host data abort on MMIO @addr + * @esr has a valid instruction syndrome and @regs holds the host x0-x30, + * SRT 31 is the zero register. Return true if the access was emulated, + * which would skip the instruction. + */ + bool (*dabt_handler)(struct user_pt_regs *regs, u64 esr, u64 addr); }; int pkvm_iommu_init(void *pool_base, unsigned int nr_pages); @@ -25,4 +32,6 @@ void *pkvm_iommu_alloc_pages(u8 order); /* Free pages from pkvm_iommu_alloc_pages(). */ void pkvm_iommu_free_pages(void *ptr); +bool pkvm_iommu_host_dabt_handler(struct user_pt_regs *regs, u64 esr, u64 addr); + #endif /* __ARM64_KVM_NVHE_IOMMU_H__ */ diff --git a/arch/arm64/kvm/hyp/nvhe/iommu.c b/arch/arm64/kvm/hyp/nvhe/iommu.c index 36432bd46c78..cdf6e87bb68e 100644 --- a/arch/arm64/kvm/hyp/nvhe/iommu.c +++ b/arch/arm64/kvm/hyp/nvhe/iommu.c @@ -149,3 +149,9 @@ void pkvm_iommu_free_pages(void *ptr) { hyp_put_page(&iommu_pages_pool, ptr); } + +bool pkvm_iommu_host_dabt_handler(struct user_pt_regs *regs, u64 esr, u64 addr) +{ + return pkvm_iommu_ops && pkvm_iommu_ops->dabt_handler && + pkvm_iommu_ops->dabt_handler(regs, esr, addr); +} diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index c14af6a4877c..523bb6bd793b 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -13,6 +13,7 @@ #include #include +#include #include #include @@ -778,6 +779,12 @@ static void host_inject_mem_abort(struct kvm_cpu_context *host_ctxt) inject_host_exception(esr); } +static bool is_dabt_with_isv(u64 esr) +{ + return (ESR_ELx_EC(esr) == ESR_ELx_EC_DABT_LOW) && + (esr & ESR_ELx_ISV); +} + void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) { struct kvm_vcpu_fault_info fault; @@ -800,6 +807,16 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) BUG_ON(!(fault.hpfar_el2 & HPFAR_EL2_NS)); addr = FIELD_GET(HPFAR_EL2_FIPA, fault.hpfar_el2) << 12; + /* + * Let the IOMMU driver emulate accesses to its MMIO. + */ + if (is_dabt_with_isv(esr) && !addr_is_memory(addr) && + pkvm_iommu_host_dabt_handler(&host_ctxt->regs, esr, + addr | FAR_TO_FIPA_OFFSET(fault.far_el2))) { + kvm_skip_host_instr(); + return; + } + switch (host_stage2_idmap(addr)) { case -EPERM: host_inject_mem_abort(host_ctxt); -- 2.56.0.176.g3575e65682-goog