Insert the appropriate UNWIND macro definition into the kvm_exc_entry in the assembly function to guide the generation of correct ORC table entries, thereby solving the timeout problem of loading the livepatch-sample module on a physical machine running multiple vcpus virtual machines.

While solving the above problems, we have gained an additional benefit, that is, we can obtain more call stack information

Stack information that can be obtained before the problem is fixed: [<0>] kvm_vcpu_block+0x88/0x120 [kvm] [<0>] kvm_vcpu_halt+0x68/0x580 [kvm] [<0>] kvm_emu_idle+0xd4/0xf0 [kvm] [<0>] kvm_handle_gspr+0x7c/0x700 [kvm] [<0>] kvm_handle_exit+0x160/0x270 [kvm] [<0>] kvm_exc_entry+0x100/0x1e0

Stack information that can be obtained after the problem is fixed: [<0>] kvm_vcpu_block+0x88/0x120 [kvm] [<0>] kvm_vcpu_halt+0x68/0x580 [kvm] [<0>] kvm_emu_idle+0xd4/0xf0 [kvm] [<0>] kvm_handle_gspr+0x7c/0x700 [kvm] [<0>] kvm_handle_exit+0x160/0x270 [kvm] [<0>] kvm_exc_entry+0x100/0x1e0 [<0>] kvm_arch_vcpu_ioctl_run+0x260/0x488 [kvm] [<0>] kvm_vcpu_ioctl+0x200/0xcd8 [kvm] [<0>] sys_ioctl+0x498/0xf00 [<0>] do_syscall+0x94/0x190 [<0>] handle_syscall+0xb8/0x158

Cc: stable@vger.kernel.org Signed-off-by: Xianglai Li lixianglai@loongson.cn --- Cc: Huacai Chen chenhuacai@kernel.org Cc: WANG Xuerui kernel@xen0n.name Cc: Tianrui Zhao zhaotianrui@loongson.cn Cc: Bibo Mao maobibo@loongson.cn Cc: Charlie Jenkins charlie@rivosinc.com Cc: Xianglai Li lixianglai@loongson.cn Cc: Thomas Gleixner tglx@linutronix.de

arch/loongarch/kvm/switch.S | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S index 93845ce53651..e3ecb24a3bc5 100644 --- a/arch/loongarch/kvm/switch.S +++ b/arch/loongarch/kvm/switch.S @@ -170,6 +170,7 @@ SYM_CODE_START(kvm_exc_entry) /* restore per cpu register */ ld.d u0, a2, KVM_ARCH_HPERCPU addi.d sp, sp, -PT_SIZE + UNWIND_HINT_REGS

/* Prepare handle exception */ or a0, s0, zero @@ -214,6 +215,7 @@ SYM_FUNC_START(kvm_enter_guest) addi.d a2, sp, -PT_SIZE /* Save host GPRs */ kvm_save_host_gpr a2 + st.d ra, a2, PT_ERA

addi.d a2, a1, KVM_VCPU_ARCH st.d sp, a2, KVM_ARCH_HSP

Hi, Xianglai,

On Wed, Dec 17, 2025 at 11:49 AM Xianglai Li lixianglai@loongson.cn wrote:

If we directly compile the switch.S file into the kernel, the address of the kvm_exc_entry function will definitely be within the DMW memory area. Therefore, we will no longer need to perform a copy relocation of kvm_exc_entry.

Based on the above description, compile switch.S directly into the kernel, and then remove the copy relocation execution logic for the kvm_exc_entry function.

Cc: stable@vger.kernel.org Signed-off-by: Xianglai Li lixianglai@loongson.cn

---

Cc: Huacai Chen chenhuacai@kernel.org Cc: WANG Xuerui kernel@xen0n.name Cc: Tianrui Zhao zhaotianrui@loongson.cn Cc: Bibo Mao maobibo@loongson.cn Cc: Charlie Jenkins charlie@rivosinc.com Cc: Xianglai Li lixianglai@loongson.cn Cc: Thomas Gleixner tglx@linutronix.de

arch/loongarch/Kbuild | 2 +- arch/loongarch/include/asm/asm-prototypes.h | 16 ++++++++++ arch/loongarch/include/asm/kvm_host.h | 5 +-- arch/loongarch/include/asm/kvm_vcpu.h | 20 ++++++------ arch/loongarch/kvm/Makefile | 2 +- arch/loongarch/kvm/main.c | 35 ++------------------- arch/loongarch/kvm/switch.S | 22 ++++++++++--- 7 files changed, 49 insertions(+), 53 deletions(-)

diff --git a/arch/loongarch/Kbuild b/arch/loongarch/Kbuild index beb8499dd8ed..1c7a0dbe5e72 100644 --- a/arch/loongarch/Kbuild +++ b/arch/loongarch/Kbuild @@ -3,7 +3,7 @@ obj-y += mm/ obj-y += net/ obj-y += vdso/

-obj-$(CONFIG_KVM) += kvm/ +obj-$(subst m,y,$(CONFIG_KVM)) += kvm/

# for cleaning subdir- += boot diff --git a/arch/loongarch/include/asm/asm-prototypes.h b/arch/loongarch/include/asm/asm-prototypes.h index 704066b4f736..eb591276d191 100644 --- a/arch/loongarch/include/asm/asm-prototypes.h +++ b/arch/loongarch/include/asm/asm-prototypes.h @@ -20,3 +20,19 @@ asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_ struct pt_regs *regs, int (*fn)(void *), void *fn_arg);

+void kvm_exc_entry(void); +int kvm_enter_guest(void *run, void *vcpu);

+#ifdef CONFIG_CPU_HAS_LSX +void kvm_save_lsx(void *fpu); +void kvm_restore_lsx(void *fpu); +#endif

+#ifdef CONFIG_CPU_HAS_LASX +void kvm_save_lasx(void *fpu); +void kvm_restore_lasx(void *fpu); +#endif

+void kvm_save_fpu(void *fpu); +void kvm_restore_fpu(void *fpu); diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h index e4fe5b8e8149..0aa7679536cc 100644 --- a/arch/loongarch/include/asm/kvm_host.h +++ b/arch/loongarch/include/asm/kvm_host.h @@ -85,7 +85,6 @@ struct kvm_context { struct kvm_world_switch { int (*exc_entry)(void); int (*enter_guest)(struct kvm_run *run, struct kvm_vcpu *vcpu);

•   unsigned long page_order;
  

};

#define MAX_PGTABLE_LEVELS 4 @@ -344,11 +343,9 @@ enum hrtimer_restart kvm_swtimer_wakeup(struct hrtimer *timer); void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, const struct kvm_memory_slot *memslot); void kvm_init_vmcs(struct kvm *kvm); void kvm_exc_entry(void); -int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu); +int kvm_enter_guest(void *run, void *vcpu);

extern unsigned long vpid_mask; -extern const unsigned long kvm_exception_size; -extern const unsigned long kvm_enter_guest_size; extern struct kvm_world_switch *kvm_loongarch_ops;

#define SW_GCSR (1 << 0) diff --git a/arch/loongarch/include/asm/kvm_vcpu.h b/arch/loongarch/include/asm/kvm_vcpu.h index 3784ab4ccdb5..8af98a3d7b0c 100644 --- a/arch/loongarch/include/asm/kvm_vcpu.h +++ b/arch/loongarch/include/asm/kvm_vcpu.h @@ -53,28 +53,28 @@ void kvm_deliver_exception(struct kvm_vcpu *vcpu);

void kvm_own_fpu(struct kvm_vcpu *vcpu); void kvm_lose_fpu(struct kvm_vcpu *vcpu); -void kvm_save_fpu(struct loongarch_fpu *fpu); -void kvm_restore_fpu(struct loongarch_fpu *fpu); +void kvm_save_fpu(void *fpu); +void kvm_restore_fpu(void *fpu);

Why are these modifications needed?

Huacai

void kvm_restore_fcsr(struct loongarch_fpu *fpu);

#ifdef CONFIG_CPU_HAS_LSX int kvm_own_lsx(struct kvm_vcpu *vcpu); -void kvm_save_lsx(struct loongarch_fpu *fpu); -void kvm_restore_lsx(struct loongarch_fpu *fpu); +void kvm_save_lsx(void *fpu); +void kvm_restore_lsx(void *fpu); #else static inline int kvm_own_lsx(struct kvm_vcpu *vcpu) { return -EINVAL; } -static inline void kvm_save_lsx(struct loongarch_fpu *fpu) { } -static inline void kvm_restore_lsx(struct loongarch_fpu *fpu) { } +static inline void kvm_save_lsx(void *fpu) { } +static inline void kvm_restore_lsx(void *fpu) { } #endif

#ifdef CONFIG_CPU_HAS_LASX int kvm_own_lasx(struct kvm_vcpu *vcpu); -void kvm_save_lasx(struct loongarch_fpu *fpu); -void kvm_restore_lasx(struct loongarch_fpu *fpu); +void kvm_save_lasx(void *fpu); +void kvm_restore_lasx(void *fpu); #else static inline int kvm_own_lasx(struct kvm_vcpu *vcpu) { return -EINVAL; } -static inline void kvm_save_lasx(struct loongarch_fpu *fpu) { } -static inline void kvm_restore_lasx(struct loongarch_fpu *fpu) { } +static inline void kvm_save_lasx(void *fpu) { } +static inline void kvm_restore_lasx(void *fpu) { } #endif

#ifdef CONFIG_CPU_HAS_LBT diff --git a/arch/loongarch/kvm/Makefile b/arch/loongarch/kvm/Makefile index cb41d9265662..fe665054f824 100644 --- a/arch/loongarch/kvm/Makefile +++ b/arch/loongarch/kvm/Makefile @@ -11,7 +11,7 @@ kvm-y += exit.o kvm-y += interrupt.o kvm-y += main.o kvm-y += mmu.o -kvm-y += switch.o +obj-y += switch.o kvm-y += timer.o kvm-y += tlb.o kvm-y += vcpu.o diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c index 80ea63d465b8..67d234540ed4 100644 --- a/arch/loongarch/kvm/main.c +++ b/arch/loongarch/kvm/main.c @@ -340,8 +340,7 @@ void kvm_arch_disable_virtualization_cpu(void)

static int kvm_loongarch_env_init(void) {

•   int cpu, order, ret;
  

•   void *addr;
  

•   int cpu, ret;
    struct kvm_context *context;
  
    vmcs = alloc_percpu(struct kvm_context);
  

@@ -357,30 +356,8 @@ static int kvm_loongarch_env_init(void) return -ENOMEM; }

•   /*
  

•    * PGD register is shared between root kernel and kvm hypervisor.
  

•    * So world switch entry should be in DMW area rather than TLB area
  

•    * to avoid page fault reenter.
  

•    *
  

•    * In future if hardware pagetable walking is supported, we won't
  

•    * need to copy world switch code to DMW area.
  

•    */
  

•   order = get_order(kvm_exception_size + kvm_enter_guest_size);
  

•   addr = (void *)__get_free_pages(GFP_KERNEL, order);
  

•   if (!addr) {
  

•           free_percpu(vmcs);
  

•           vmcs = NULL;
  

•           kfree(kvm_loongarch_ops);
  

•           kvm_loongarch_ops = NULL;
  

•           return -ENOMEM;
  

•   }
  

•   memcpy(addr, kvm_exc_entry, kvm_exception_size);
  

•   memcpy(addr + kvm_exception_size, kvm_enter_guest, kvm_enter_guest_size);
  

•   flush_icache_range((unsigned long)addr, (unsigned long)addr + kvm_exception_size + kvm_enter_guest_size);
  

•   kvm_loongarch_ops->exc_entry = addr;
  

•   kvm_loongarch_ops->enter_guest = addr + kvm_exception_size;
  

•   kvm_loongarch_ops->page_order = order;
  

•   kvm_loongarch_ops->exc_entry = (void *)kvm_exc_entry;
  

•   kvm_loongarch_ops->enter_guest = (void *)kvm_enter_guest;
  
    vpid_mask = read_csr_gstat();
    vpid_mask = (vpid_mask & CSR_GSTAT_GIDBIT) >> CSR_GSTAT_GIDBIT_SHIFT;
  

@@ -414,16 +391,10 @@ static int kvm_loongarch_env_init(void)

static void kvm_loongarch_env_exit(void) {

•   unsigned long addr;
  

•   if (vmcs)
            free_percpu(vmcs);
  
    if (kvm_loongarch_ops) {
  

•           if (kvm_loongarch_ops->exc_entry) {
  

•                   addr = (unsigned long)kvm_loongarch_ops->exc_entry;
  

•                   free_pages(addr, kvm_loongarch_ops->page_order);
  

•           }
            kfree(kvm_loongarch_ops);
    }
  
  

diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S index f1768b7a6194..93845ce53651 100644 --- a/arch/loongarch/kvm/switch.S +++ b/arch/loongarch/kvm/switch.S @@ -5,6 +5,7 @@

#include <linux/linkage.h> #include <asm/asm.h> +#include <asm/page.h> #include <asm/asmmacro.h> #include <asm/loongarch.h> #include <asm/regdef.h> @@ -100,10 +101,18 @@ * - is still in guest mode, such as pgd table/vmid registers etc, * - will fix with hw page walk enabled in future * load kvm_vcpu from reserved CSR KVM_VCPU_KS, and save a2 to KVM_TEMP_KS

•    *
  

•    * PGD register is shared between root kernel and kvm hypervisor.
  

•    * So world switch entry should be in DMW area rather than TLB area
  

•    * to avoid page fault reenter.
  

•    *
  

•    * In future if hardware pagetable walking is supported, we won't
  

•    * need to copy world switch code to DMW area.
     */
    .text
    .cfi_sections   .debug_frame
  

SYM_CODE_START(kvm_exc_entry)

•   .p2align PAGE_SHIFT
    UNWIND_HINT_UNDEFINED
    csrwr   a2,   KVM_TEMP_KS
    csrrd   a2,   KVM_VCPU_KS
  

@@ -190,8 +199,8 @@ ret_to_host: kvm_restore_host_gpr a2 jr ra

-SYM_INNER_LABEL(kvm_exc_entry_end, SYM_L_LOCAL) SYM_CODE_END(kvm_exc_entry) +EXPORT_SYMBOL(kvm_exc_entry)

/*

• int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu)

@@ -215,8 +224,8 @@ SYM_FUNC_START(kvm_enter_guest) /* Save kvm_vcpu to kscratch */ csrwr a1, KVM_VCPU_KS kvm_switch_to_guest -SYM_INNER_LABEL(kvm_enter_guest_end, SYM_L_LOCAL) SYM_FUNC_END(kvm_enter_guest) +EXPORT_SYMBOL(kvm_enter_guest)

SYM_FUNC_START(kvm_save_fpu) fpu_save_csr a0 t1 @@ -224,6 +233,7 @@ SYM_FUNC_START(kvm_save_fpu) fpu_save_cc a0 t1 t2 jr ra SYM_FUNC_END(kvm_save_fpu) +EXPORT_SYMBOL(kvm_save_fpu)

SYM_FUNC_START(kvm_restore_fpu) fpu_restore_double a0 t1 @@ -231,6 +241,7 @@ SYM_FUNC_START(kvm_restore_fpu) fpu_restore_cc a0 t1 t2 jr ra SYM_FUNC_END(kvm_restore_fpu) +EXPORT_SYMBOL(kvm_restore_fpu)

#ifdef CONFIG_CPU_HAS_LSX SYM_FUNC_START(kvm_save_lsx) @@ -239,6 +250,7 @@ SYM_FUNC_START(kvm_save_lsx) lsx_save_data a0 t1 jr ra SYM_FUNC_END(kvm_save_lsx) +EXPORT_SYMBOL(kvm_save_lsx)

SYM_FUNC_START(kvm_restore_lsx) lsx_restore_data a0 t1 @@ -246,6 +258,7 @@ SYM_FUNC_START(kvm_restore_lsx) fpu_restore_csr a0 t1 t2 jr ra SYM_FUNC_END(kvm_restore_lsx) +EXPORT_SYMBOL(kvm_restore_lsx) #endif

#ifdef CONFIG_CPU_HAS_LASX @@ -255,6 +268,7 @@ SYM_FUNC_START(kvm_save_lasx) lasx_save_data a0 t1 jr ra SYM_FUNC_END(kvm_save_lasx) +EXPORT_SYMBOL(kvm_save_lasx)

SYM_FUNC_START(kvm_restore_lasx) lasx_restore_data a0 t1 @@ -262,10 +276,8 @@ SYM_FUNC_START(kvm_restore_lasx) fpu_restore_csr a0 t1 t2 jr ra SYM_FUNC_END(kvm_restore_lasx) +EXPORT_SYMBOL(kvm_restore_lasx) #endif

•   .section ".rodata"
  

-SYM_DATA(kvm_exception_size, .quad kvm_exc_entry_end - kvm_exc_entry) -SYM_DATA(kvm_enter_guest_size, .quad kvm_enter_guest_end - kvm_enter_guest)

#ifdef CONFIG_CPU_HAS_LBT STACK_FRAME_NON_STANDARD kvm_restore_fpu -- 2.39.1