From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> The 32-bit process needs to use TLS in libc, so a hypercall is introduced to load the guest TLS into the host GDT. The checking of the guest TLS is the same as tls_desc_okay() in the arch/x86/kernel/tls.c file. Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx> --- arch/x86/kvm/pvm/pvm.c | 81 ++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/pvm/pvm.h | 1 + 2 files changed, 82 insertions(+) diff --git a/arch/x86/kvm/pvm/pvm.c b/arch/x86/kvm/pvm/pvm.c index ee55e99fb204..e68052f33186 100644 --- a/arch/x86/kvm/pvm/pvm.c +++ b/arch/x86/kvm/pvm/pvm.c @@ -281,6 +281,26 @@ static void segments_save_guest_and_switch_to_host(struct vcpu_pvm *pvm) wrmsrl(MSR_FS_BASE, current->thread.fsbase); } +/* + * Load guest TLS entries into the GDT. + */ +static inline void host_gdt_set_tls(struct vcpu_pvm *pvm) +{ + struct desc_struct *gdt = get_current_gdt_rw(); + unsigned int i; + + for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++) + gdt[GDT_ENTRY_TLS_MIN + i] = pvm->tls_array[i]; +} + +/* + * Load current task's TLS into the GDT. + */ +static inline void host_gdt_restore_tls(void) +{ + native_load_tls(¤t->thread, smp_processor_id()); +} + static void pvm_prepare_switch_to_guest(struct kvm_vcpu *vcpu) { struct vcpu_pvm *pvm = to_pvm(vcpu); @@ -304,6 +324,8 @@ static void pvm_prepare_switch_to_guest(struct kvm_vcpu *vcpu) native_tss_invalidate_io_bitmap(); #endif + host_gdt_set_tls(pvm); + #ifdef CONFIG_MODIFY_LDT_SYSCALL /* PVM doesn't support LDT. */ if (unlikely(current->mm->context.ldt)) @@ -334,6 +356,8 @@ static void pvm_prepare_switch_to_host(struct vcpu_pvm *pvm) kvm_load_ldt(GDT_ENTRY_LDT*8); #endif + host_gdt_restore_tls(); + segments_save_guest_and_switch_to_host(pvm); pvm->loaded_cpu_state = 0; } @@ -1629,6 +1653,60 @@ static int handle_hc_wrmsr(struct kvm_vcpu *vcpu, u32 index, u64 value) return 1; } +// Check if the tls desc is allowed on the host GDT. +// The same logic as tls_desc_okay() in arch/x86/kernel/tls.c. +static bool tls_desc_okay(struct desc_struct *desc) +{ + // Only allow present segments. + if (!desc->p) + return false; + + // Only allow data segments. + if (desc->type & (1 << 3)) + return false; + + // Only allow 32-bit data segments. + if (!desc->d) + return false; + + return true; +} + +/* + * Hypercall: PVM_HC_LOAD_TLS + * Load guest TLS desc into host GDT. + */ +static int handle_hc_load_tls(struct kvm_vcpu *vcpu, unsigned long tls_desc_0, + unsigned long tls_desc_1, unsigned long tls_desc_2) +{ + struct vcpu_pvm *pvm = to_pvm(vcpu); + unsigned long *tls_array = (unsigned long *)&pvm->tls_array[0]; + int i; + + tls_array[0] = tls_desc_0; + tls_array[1] = tls_desc_1; + tls_array[2] = tls_desc_2; + + for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++) { + if (!tls_desc_okay(&pvm->tls_array[i])) { + pvm->tls_array[i] = (struct desc_struct){0}; + continue; + } + /* Standarding TLS descs, same as fill_ldt(). */ + pvm->tls_array[i].type |= 1; + pvm->tls_array[i].s = 1; + pvm->tls_array[i].dpl = 0x3; + pvm->tls_array[i].l = 0; + } + + preempt_disable(); + if (pvm->loaded_cpu_state) + host_gdt_set_tls(pvm); + preempt_enable(); + + return 1; +} + static int handle_kvm_hypercall(struct kvm_vcpu *vcpu) { int r; @@ -1679,6 +1757,8 @@ static int handle_exit_syscall(struct kvm_vcpu *vcpu) return handle_hc_rdmsr(vcpu, a0); case PVM_HC_WRMSR: return handle_hc_wrmsr(vcpu, a0, a1); + case PVM_HC_LOAD_TLS: + return handle_hc_load_tls(vcpu, a0, a1, a2); default: return handle_kvm_hypercall(vcpu); } @@ -2296,6 +2376,7 @@ static void pvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) pvm->hw_ss = __USER_DS; pvm->int_shadow = 0; pvm->nmi_mask = false; + memset(&pvm->tls_array[0], 0, sizeof(pvm->tls_array)); pvm->msr_vcpu_struct = 0; pvm->msr_supervisor_rsp = 0; diff --git a/arch/x86/kvm/pvm/pvm.h b/arch/x86/kvm/pvm/pvm.h index 31060831e009..f28ab0b48f40 100644 --- a/arch/x86/kvm/pvm/pvm.h +++ b/arch/x86/kvm/pvm/pvm.h @@ -98,6 +98,7 @@ struct vcpu_pvm { struct kvm_segment segments[NR_VCPU_SREG]; struct desc_ptr idt_ptr; struct desc_ptr gdt_ptr; + struct desc_struct tls_array[GDT_ENTRY_TLS_ENTRIES]; }; struct kvm_pvm { -- 2.19.1.6.gb485710b