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Tue, 10 Mar 2026 05:49:45 -0700 (PDT) Date: Tue, 10 Mar 2026 12:49:22 +0000 In-Reply-To: <20260310124933.830025-1-sebastianene@google.com> Mime-Version: 1.0 References: <20260310124933.830025-1-sebastianene@google.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260310124933.830025-4-sebastianene@google.com> Subject: [PATCH 03/14] KVM: arm64: Support host MMIO trap handlers for unmapped devices From: Sebastian Ene To: alexandru.elisei@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com Cc: 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, sebastianene@google.com, smostafa@google.com, suzuki.poulose@arm.com, tabba@google.com, tglx@kernel.org, vdonnefort@google.com, bgrzesik@google.com, will@kernel.org, yuzenghui@huawei.com Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260310_054948_314695_52313F8A X-CRM114-Status: GOOD ( 17.56 ) 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 Introduce a mechanism to register callbacks for MMIO accesses to regions unmapped from the host Stage-2 page tables. This infrastructure allows the hypervisor to intercept host accesses to protected or emulated devices. When a Stage-2 fault occurs on a registered device region, the hypervisor will invoke the associated callback to emulate the access. Signed-off-by: Sebastian Ene --- arch/arm64/include/asm/kvm_arm.h | 3 ++ arch/arm64/include/asm/kvm_pkvm.h | 6 ++++ arch/arm64/kvm/hyp/nvhe/mem_protect.c | 41 +++++++++++++++++++++++++++ arch/arm64/kvm/hyp/nvhe/setup.c | 3 ++ 4 files changed, 53 insertions(+) diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h index 3f9233b5a130..8fe1e80ab3f4 100644 --- a/arch/arm64/include/asm/kvm_arm.h +++ b/arch/arm64/include/asm/kvm_arm.h @@ -304,6 +304,9 @@ /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */ #define HPFAR_MASK (~UL(0xf)) + +#define FAR_MASK GENMASK_ULL(11, 0) + /* * We have * PAR [PA_Shift - 1 : 12] = PA [PA_Shift - 1 : 12] diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h index 48ec7d519399..5321ced2f50a 100644 --- a/arch/arm64/include/asm/kvm_pkvm.h +++ b/arch/arm64/include/asm/kvm_pkvm.h @@ -19,9 +19,15 @@ #define PKVM_PROTECTED_REGS_NUM 8 +struct pkvm_protected_reg; + +typedef void (pkvm_emulate_handler)(struct pkvm_protected_reg *region, u64 offset, bool write, + u64 *reg, u8 reg_size); + struct pkvm_protected_reg { u64 start_pfn; size_t num_pages; + pkvm_emulate_handler *cb; }; extern struct pkvm_protected_reg kvm_nvhe_sym(pkvm_protected_regs)[]; diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 7c125836b533..f405d2fbd88f 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 @@ -608,6 +609,41 @@ static int host_stage2_idmap(u64 addr) return ret; } +static bool handle_host_mmio_trap(struct kvm_cpu_context *host_ctxt, u64 esr, u64 addr) +{ + u64 offset, reg_value = 0, start, end; + u8 reg_size, reg_index; + bool write; + int i; + + for (i = 0; i < num_protected_reg; i++) { + start = pkvm_protected_regs[i].start_pfn << PAGE_SHIFT; + end = start + (pkvm_protected_regs[i].num_pages << PAGE_SHIFT); + + if (start > addr || addr > end) + continue; + + reg_size = BIT((esr & ESR_ELx_SAS) >> ESR_ELx_SAS_SHIFT); + reg_index = (esr & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT; + write = (esr & ESR_ELx_WNR) == ESR_ELx_WNR; + offset = addr - start; + + if (write) + reg_value = host_ctxt->regs.regs[reg_index]; + + pkvm_protected_regs[i].cb(&pkvm_protected_regs[i], offset, write, + ®_value, reg_size); + + if (!write) + host_ctxt->regs.regs[reg_index] = reg_value; + + kvm_skip_host_instr(); + return true; + } + + return false; +} + void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) { struct kvm_vcpu_fault_info fault; @@ -630,6 +666,11 @@ 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; + addr |= fault.far_el2 & FAR_MASK; + + if (ESR_ELx_EC(esr) == ESR_ELx_EC_DABT_LOW && !addr_is_memory(addr) && + handle_host_mmio_trap(host_ctxt, esr, addr)) + return; ret = host_stage2_idmap(addr); BUG_ON(ret && ret != -EAGAIN); diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c index ad5b96085e1b..f91dfebe9980 100644 --- a/arch/arm64/kvm/hyp/nvhe/setup.c +++ b/arch/arm64/kvm/hyp/nvhe/setup.c @@ -296,6 +296,9 @@ static int unmap_protected_regions(void) if (ret) goto err_setup; } + + if (reg->cb) + reg->cb = kern_hyp_va(reg->cb); } return 0; -- 2.53.0.473.g4a7958ca14-goog