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Tue, 24 Feb 2026 19:50:58 -0800 (PST) Received: from rhel9-box.lan ([122.176.129.56]) by smtp.googlemail.com with ESMTPSA id 98e67ed59e1d1-359018838b2sm1186006a91.5.2026.02.24.19.50.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Feb 2026 19:50:58 -0800 (PST) From: Ani Sinha To: Paolo Bonzini Cc: Ani Sinha , kraxel@redhat.com, ani@anisinha.ca, kvm@vger.kernel.org, qemu-devel@nongnu.org Subject: [PATCH v6 15/35] accel/kvm: rebind current VCPUs to the new KVM VM file descriptor upon reset Date: Wed, 25 Feb 2026 09:19:20 +0530 Message-ID: <20260225035000.385950-16-anisinha@redhat.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20260225035000.385950-1-anisinha@redhat.com> References: <20260225035000.385950-1-anisinha@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Confidential guests needs to generate a new KVM file descriptor upon virtual machine reset. Existing VCPUs needs to be reattached to this new KVM VM file descriptor. As a part of this, new VCPU file descriptors against this new KVM VM file descriptor needs to be created and re-initialized. Resources allocated against the old VCPU fds needs to be released. This change makes this happen. Signed-off-by: Ani Sinha --- accel/kvm/kvm-all.c | 215 +++++++++++++++++++++++++++++++++-------- accel/kvm/trace-events | 1 + 2 files changed, 174 insertions(+), 42 deletions(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index d244156f6f..a347a71a2e 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -127,6 +127,10 @@ static NotifierList kvm_irqchip_change_notifiers = static NotifierWithReturnList register_vmfd_changed_notifiers = NOTIFIER_WITH_RETURN_LIST_INITIALIZER(register_vmfd_changed_notifiers); +static int map_kvm_run(KVMState *s, CPUState *cpu, Error **errp); +static int map_kvm_dirty_gfns(KVMState *s, CPUState *cpu, Error **errp); +static int vcpu_unmap_regions(KVMState *s, CPUState *cpu); + struct KVMResampleFd { int gsi; EventNotifier *resample_event; @@ -420,6 +424,90 @@ err: return ret; } +static void kvm_create_vcpu_internal(CPUState *cpu, KVMState *s, int kvm_fd) +{ + cpu->kvm_fd = kvm_fd; + cpu->kvm_state = s; + if (!s->guest_state_protected) { + cpu->vcpu_dirty = true; + } + cpu->dirty_pages = 0; + cpu->throttle_us_per_full = 0; + + return; +} + +static int kvm_rebind_vcpus(Error **errp) +{ + CPUState *cpu; + unsigned long vcpu_id; + KVMState *s = kvm_state; + int kvm_fd, ret = 0; + + CPU_FOREACH(cpu) { + vcpu_id = kvm_arch_vcpu_id(cpu); + + if (cpu->kvm_fd) { + close(cpu->kvm_fd); + } + + ret = kvm_arch_destroy_vcpu(cpu); + if (ret < 0) { + goto err; + } + + if (s->coalesced_mmio_ring == (void *)cpu->kvm_run + PAGE_SIZE) { + s->coalesced_mmio_ring = NULL; + } + + ret = vcpu_unmap_regions(s, cpu); + if (ret < 0) { + goto err; + } + + ret = kvm_arch_pre_create_vcpu(cpu, errp); + if (ret < 0) { + goto err; + } + + kvm_fd = kvm_vm_ioctl(s, KVM_CREATE_VCPU, vcpu_id); + if (kvm_fd < 0) { + error_report("KVM_CREATE_VCPU IOCTL failed for vCPU %lu (%s)", + vcpu_id, strerror(kvm_fd)); + return kvm_fd; + } + + kvm_create_vcpu_internal(cpu, s, kvm_fd); + + ret = map_kvm_run(s, cpu, errp); + if (ret < 0) { + goto err; + } + + if (s->kvm_dirty_ring_size) { + ret = map_kvm_dirty_gfns(s, cpu, errp); + if (ret < 0) { + goto err; + } + } + + ret = kvm_arch_init_vcpu(cpu); + if (ret < 0) { + error_setg_errno(errp, -ret, + "kvm_init_vcpu: kvm_arch_init_vcpu failed (%lu)", + vcpu_id); + } + + close(cpu->kvm_vcpu_stats_fd); + cpu->kvm_vcpu_stats_fd = kvm_vcpu_ioctl(cpu, KVM_GET_STATS_FD, NULL); + kvm_init_cpu_signals(cpu); + } + trace_kvm_rebind_vcpus(); + + err: + return ret; +} + static void kvm_park_vcpu(CPUState *cpu) { struct KVMParkedVcpu *vcpu; @@ -483,13 +571,7 @@ static int kvm_create_vcpu(CPUState *cpu) } } - cpu->kvm_fd = kvm_fd; - cpu->kvm_state = s; - if (!s->guest_state_protected) { - cpu->vcpu_dirty = true; - } - cpu->dirty_pages = 0; - cpu->throttle_us_per_full = 0; + kvm_create_vcpu_internal(cpu, s, kvm_fd); trace_kvm_create_vcpu(cpu->cpu_index, vcpu_id, kvm_fd); @@ -508,19 +590,11 @@ int kvm_create_and_park_vcpu(CPUState *cpu) return ret; } -static int do_kvm_destroy_vcpu(CPUState *cpu) +static int vcpu_unmap_regions(KVMState *s, CPUState *cpu) { - KVMState *s = kvm_state; int mmap_size; int ret = 0; - trace_kvm_destroy_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu)); - - ret = kvm_arch_destroy_vcpu(cpu); - if (ret < 0) { - goto err; - } - mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0); if (mmap_size < 0) { ret = mmap_size; @@ -548,39 +622,47 @@ static int do_kvm_destroy_vcpu(CPUState *cpu) cpu->kvm_dirty_gfns = NULL; } - kvm_park_vcpu(cpu); -err: + err: return ret; } -void kvm_destroy_vcpu(CPUState *cpu) -{ - if (do_kvm_destroy_vcpu(cpu) < 0) { - error_report("kvm_destroy_vcpu failed"); - exit(EXIT_FAILURE); - } -} - -int kvm_init_vcpu(CPUState *cpu, Error **errp) +static int do_kvm_destroy_vcpu(CPUState *cpu) { KVMState *s = kvm_state; - int mmap_size; - int ret; + int ret = 0; - trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu)); + trace_kvm_destroy_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu)); - ret = kvm_arch_pre_create_vcpu(cpu, errp); + ret = kvm_arch_destroy_vcpu(cpu); if (ret < 0) { goto err; } - ret = kvm_create_vcpu(cpu); + /* If I am the CPU that created coalesced_mmio_ring, then discard it */ + if (s->coalesced_mmio_ring == (void *)cpu->kvm_run + PAGE_SIZE) { + s->coalesced_mmio_ring = NULL; + } + + ret = vcpu_unmap_regions(s, cpu); if (ret < 0) { - error_setg_errno(errp, -ret, - "kvm_init_vcpu: kvm_create_vcpu failed (%lu)", - kvm_arch_vcpu_id(cpu)); goto err; } + kvm_park_vcpu(cpu); +err: + return ret; +} + +void kvm_destroy_vcpu(CPUState *cpu) +{ + if (do_kvm_destroy_vcpu(cpu) < 0) { + error_report("kvm_destroy_vcpu failed"); + exit(EXIT_FAILURE); + } +} + +static int map_kvm_run(KVMState *s, CPUState *cpu, Error **errp) +{ + int mmap_size, ret = 0; mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0); if (mmap_size < 0) { @@ -605,14 +687,53 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp) (void *)cpu->kvm_run + s->coalesced_mmio * PAGE_SIZE; } + err: + return ret; +} + +static int map_kvm_dirty_gfns(KVMState *s, CPUState *cpu, Error **errp) +{ + int ret = 0; + /* Use MAP_SHARED to share pages with the kernel */ + cpu->kvm_dirty_gfns = mmap(NULL, s->kvm_dirty_ring_bytes, + PROT_READ | PROT_WRITE, MAP_SHARED, + cpu->kvm_fd, + PAGE_SIZE * KVM_DIRTY_LOG_PAGE_OFFSET); + if (cpu->kvm_dirty_gfns == MAP_FAILED) { + ret = -errno; + } + + return ret; +} + +int kvm_init_vcpu(CPUState *cpu, Error **errp) +{ + KVMState *s = kvm_state; + int ret; + + trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu)); + + ret = kvm_arch_pre_create_vcpu(cpu, errp); + if (ret < 0) { + goto err; + } + + ret = kvm_create_vcpu(cpu); + if (ret < 0) { + error_setg_errno(errp, -ret, + "kvm_init_vcpu: kvm_create_vcpu failed (%lu)", + kvm_arch_vcpu_id(cpu)); + goto err; + } + + ret = map_kvm_run(s, cpu, errp); + if (ret < 0) { + goto err; + } + if (s->kvm_dirty_ring_size) { - /* Use MAP_SHARED to share pages with the kernel */ - cpu->kvm_dirty_gfns = mmap(NULL, s->kvm_dirty_ring_bytes, - PROT_READ | PROT_WRITE, MAP_SHARED, - cpu->kvm_fd, - PAGE_SIZE * KVM_DIRTY_LOG_PAGE_OFFSET); - if (cpu->kvm_dirty_gfns == MAP_FAILED) { - ret = -errno; + ret = map_kvm_dirty_gfns(s, cpu, errp); + if (ret < 0) { goto err; } } @@ -2710,6 +2831,16 @@ static int kvm_reset_vmfd(MachineState *ms) } assert(!err); + /* + * rebind new vcpu fds with the new kvm fds + * These can only be called after kvm_arch_on_vmfd_change() + */ + ret = kvm_rebind_vcpus(&err); + if (ret < 0) { + return ret; + } + assert(!err); + /* these can be only called after ram_block_rebind() */ memory_listener_register(&kml->listener, &address_space_memory); memory_listener_register(&kvm_io_listener, &address_space_io); diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events index e4beda0148..4a8921c632 100644 --- a/accel/kvm/trace-events +++ b/accel/kvm/trace-events @@ -15,6 +15,7 @@ kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu" kvm_unpark_vcpu(unsigned long arch_cpu_id, const char *msg) "id: %lu %s" kvm_irqchip_commit_routes(void) "" kvm_reset_vmfd(void) "" +kvm_rebind_vcpus(void) "" kvm_irqchip_add_msi_route(char *name, int vector, int virq) "dev %s vector %d virq %d" kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d" kvm_irqchip_release_virq(int virq) "virq %d" -- 2.42.0