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 | 21 +++++++++++++
arch/loongarch/include/asm/kvm_host.h | 3 --
arch/loongarch/kvm/Makefile | 2 +-
arch/loongarch/kvm/main.c | 35 ++-------------------
arch/loongarch/kvm/switch.S | 22 ++++++++++---
6 files changed, 43 insertions(+), 42 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..e8ce153691e5 100644
--- a/arch/loongarch/include/asm/asm-prototypes.h
+++ b/arch/loongarch/include/asm/asm-prototypes.h
@@ -20,3 +20,24 @@ asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_
struct pt_regs *regs,
int (*fn)(void *),
void *fn_arg);
+
+struct kvm_run;
+struct kvm_vcpu;
+
+void kvm_exc_entry(void);
+int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu);
+
+struct loongarch_fpu;
+
+#ifdef CONFIG_CPU_HAS_LSX
+void kvm_save_lsx(struct loongarch_fpu *fpu);
+void kvm_restore_lsx(struct loongarch_fpu *fpu);
+#endif
+
+#ifdef CONFIG_CPU_HAS_LASX
+void kvm_save_lasx(struct loongarch_fpu *fpu);
+void kvm_restore_lasx(struct loongarch_fpu *fpu);
+#endif
+
+void kvm_save_fpu(struct loongarch_fpu *fpu);
+void kvm_restore_fpu(struct loongarch_fpu *fpu);
diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index e4fe5b8e8149..1a1be10e3803 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
@@ -347,8 +346,6 @@ void kvm_exc_entry(void);
int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *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/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
On 2025/12/22 下午7:34, Xianglai Li 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 | 21 +++++++++++++
> arch/loongarch/include/asm/kvm_host.h | 3 --
> arch/loongarch/kvm/Makefile | 2 +-
> arch/loongarch/kvm/main.c | 35 ++-------------------
> arch/loongarch/kvm/switch.S | 22 ++++++++++---
> 6 files changed, 43 insertions(+), 42 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..e8ce153691e5 100644
> --- a/arch/loongarch/include/asm/asm-prototypes.h
> +++ b/arch/loongarch/include/asm/asm-prototypes.h
> @@ -20,3 +20,24 @@ asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_
> struct pt_regs *regs,
> int (*fn)(void *),
> void *fn_arg);
> +
> +struct kvm_run;
> +struct kvm_vcpu;
> +
> +void kvm_exc_entry(void);
> +int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu);
> +
> +struct loongarch_fpu;
> +
> +#ifdef CONFIG_CPU_HAS_LSX
> +void kvm_save_lsx(struct loongarch_fpu *fpu);
> +void kvm_restore_lsx(struct loongarch_fpu *fpu);
> +#endif
> +
> +#ifdef CONFIG_CPU_HAS_LASX
> +void kvm_save_lasx(struct loongarch_fpu *fpu);
> +void kvm_restore_lasx(struct loongarch_fpu *fpu);
> +#endif
> +
> +void kvm_save_fpu(struct loongarch_fpu *fpu);
> +void kvm_restore_fpu(struct loongarch_fpu *fpu);
> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> index e4fe5b8e8149..1a1be10e3803 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
> @@ -347,8 +346,6 @@ void kvm_exc_entry(void);
> int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *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/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)
one small nit, could EXPORT_SYMBOL_FOR_KVM() be used here compared with
EXPORT_SYMBOL()?
Regards
Bibo Mao
>
> 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
>
Hi Bibo Mao:
>
>
> On 2025/12/22 下午7:34, Xianglai Li 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 | 21 +++++++++++++
>> arch/loongarch/include/asm/kvm_host.h | 3 --
>> arch/loongarch/kvm/Makefile | 2 +-
>> arch/loongarch/kvm/main.c | 35 ++-------------------
>> arch/loongarch/kvm/switch.S | 22 ++++++++++---
>> 6 files changed, 43 insertions(+), 42 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..e8ce153691e5 100644
>> --- a/arch/loongarch/include/asm/asm-prototypes.h
>> +++ b/arch/loongarch/include/asm/asm-prototypes.h
>> @@ -20,3 +20,24 @@ asmlinkage void noinstr __no_stack_protector
>> ret_from_kernel_thread(struct task_
>> struct pt_regs *regs,
>> int (*fn)(void *),
>> void *fn_arg);
>> +
>> +struct kvm_run;
>> +struct kvm_vcpu;
>> +
>> +void kvm_exc_entry(void);
>> +int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu);
>> +
>> +struct loongarch_fpu;
>> +
>> +#ifdef CONFIG_CPU_HAS_LSX
>> +void kvm_save_lsx(struct loongarch_fpu *fpu);
>> +void kvm_restore_lsx(struct loongarch_fpu *fpu);
>> +#endif
>> +
>> +#ifdef CONFIG_CPU_HAS_LASX
>> +void kvm_save_lasx(struct loongarch_fpu *fpu);
>> +void kvm_restore_lasx(struct loongarch_fpu *fpu);
>> +#endif
>> +
>> +void kvm_save_fpu(struct loongarch_fpu *fpu);
>> +void kvm_restore_fpu(struct loongarch_fpu *fpu);
>> diff --git a/arch/loongarch/include/asm/kvm_host.h
>> b/arch/loongarch/include/asm/kvm_host.h
>> index e4fe5b8e8149..1a1be10e3803 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
>> @@ -347,8 +346,6 @@ void kvm_exc_entry(void);
>> int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *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/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)
> one small nit, could EXPORT_SYMBOL_FOR_KVM() be used here compared
> with EXPORT_SYMBOL()?
>
Ok! will fix it in next version
Thanks!
Xianglai.
> Regards
> Bibo Mao
>> 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
>>
Hi, Xianglai,
On Tue, Dec 23, 2025 at 10:38 AM lixianglai <lixianglai@loongson.cn> wrote:
>
> Hi Bibo Mao:
> >
> >
> > On 2025/12/22 下午7:34, Xianglai Li 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 | 21 +++++++++++++
> >> arch/loongarch/include/asm/kvm_host.h | 3 --
> >> arch/loongarch/kvm/Makefile | 2 +-
> >> arch/loongarch/kvm/main.c | 35 ++-------------------
> >> arch/loongarch/kvm/switch.S | 22 ++++++++++---
> >> 6 files changed, 43 insertions(+), 42 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..e8ce153691e5 100644
> >> --- a/arch/loongarch/include/asm/asm-prototypes.h
> >> +++ b/arch/loongarch/include/asm/asm-prototypes.h
> >> @@ -20,3 +20,24 @@ asmlinkage void noinstr __no_stack_protector
> >> ret_from_kernel_thread(struct task_
> >> struct pt_regs *regs,
> >> int (*fn)(void *),
> >> void *fn_arg);
> >> +
> >> +struct kvm_run;
> >> +struct kvm_vcpu;
> >> +
> >> +void kvm_exc_entry(void);
> >> +int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu);
> >> +
> >> +struct loongarch_fpu;
> >> +
> >> +#ifdef CONFIG_CPU_HAS_LSX
> >> +void kvm_save_lsx(struct loongarch_fpu *fpu);
> >> +void kvm_restore_lsx(struct loongarch_fpu *fpu);
> >> +#endif
> >> +
> >> +#ifdef CONFIG_CPU_HAS_LASX
> >> +void kvm_save_lasx(struct loongarch_fpu *fpu);
> >> +void kvm_restore_lasx(struct loongarch_fpu *fpu);
> >> +#endif
> >> +
> >> +void kvm_save_fpu(struct loongarch_fpu *fpu);
> >> +void kvm_restore_fpu(struct loongarch_fpu *fpu);
> >> diff --git a/arch/loongarch/include/asm/kvm_host.h
> >> b/arch/loongarch/include/asm/kvm_host.h
> >> index e4fe5b8e8149..1a1be10e3803 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
> >> @@ -347,8 +346,6 @@ void kvm_exc_entry(void);
> >> int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *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/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
I'm not sure, but if this line can be moved after .text, it seems better.
Huacai
> >> 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)
> > one small nit, could EXPORT_SYMBOL_FOR_KVM() be used here compared
> > with EXPORT_SYMBOL()?
> >
>
> Ok! will fix it in next version
> Thanks!
> Xianglai.
>
> > Regards
> > Bibo Mao
> >> 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
> >>
>
>
Hi Huacai Chen:
> Hi, Xianglai,
>
> On Tue, Dec 23, 2025 at 10:38 AM lixianglai <lixianglai@loongson.cn> wrote:
>> Hi Bibo Mao:
>>>
>>> On 2025/12/22 下午7:34, Xianglai Li 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 | 21 +++++++++++++
>>>> arch/loongarch/include/asm/kvm_host.h | 3 --
>>>> arch/loongarch/kvm/Makefile | 2 +-
>>>> arch/loongarch/kvm/main.c | 35 ++-------------------
>>>> arch/loongarch/kvm/switch.S | 22 ++++++++++---
>>>> 6 files changed, 43 insertions(+), 42 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..e8ce153691e5 100644
>>>> --- a/arch/loongarch/include/asm/asm-prototypes.h
>>>> +++ b/arch/loongarch/include/asm/asm-prototypes.h
>>>> @@ -20,3 +20,24 @@ asmlinkage void noinstr __no_stack_protector
>>>> ret_from_kernel_thread(struct task_
>>>> struct pt_regs *regs,
>>>> int (*fn)(void *),
>>>> void *fn_arg);
>>>> +
>>>> +struct kvm_run;
>>>> +struct kvm_vcpu;
>>>> +
>>>> +void kvm_exc_entry(void);
>>>> +int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu);
>>>> +
>>>> +struct loongarch_fpu;
>>>> +
>>>> +#ifdef CONFIG_CPU_HAS_LSX
>>>> +void kvm_save_lsx(struct loongarch_fpu *fpu);
>>>> +void kvm_restore_lsx(struct loongarch_fpu *fpu);
>>>> +#endif
>>>> +
>>>> +#ifdef CONFIG_CPU_HAS_LASX
>>>> +void kvm_save_lasx(struct loongarch_fpu *fpu);
>>>> +void kvm_restore_lasx(struct loongarch_fpu *fpu);
>>>> +#endif
>>>> +
>>>> +void kvm_save_fpu(struct loongarch_fpu *fpu);
>>>> +void kvm_restore_fpu(struct loongarch_fpu *fpu);
>>>> diff --git a/arch/loongarch/include/asm/kvm_host.h
>>>> b/arch/loongarch/include/asm/kvm_host.h
>>>> index e4fe5b8e8149..1a1be10e3803 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
>>>> @@ -347,8 +346,6 @@ void kvm_exc_entry(void);
>>>> int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *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/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
> I'm not sure, but if this line can be moved after .text, it seems better.
I will try and test it as suggested, and if it works, I will fix it
Thanks!
Xianglai.
> Huacai
>
>>>> 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)
>>> one small nit, could EXPORT_SYMBOL_FOR_KVM() be used here compared
>>> with EXPORT_SYMBOL()?
>>>
>> Ok! will fix it in next version
>> Thanks!
>> Xianglai.
>>
>>> Regards
>>> Bibo Mao
>>>> 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
>>>>
>>
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