LoongArch: KVM: Add Binary Translation extension support

Loongson Binary Translation (LBT) is used to accelerate binary translation,
which contains 4 scratch registers (scr0 to scr3), x86/ARM eflags (eflags)
and x87 fpu stack pointer (ftop).

Like FPU extension, here a lazy enabling method is used for LBT. the LBT
context is saved/restored on the vcpu context switch path.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index 5f0677e..5262cec 100644 (file)
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -133,8 +133,9 @@ enum emulation_result {
 #define KVM_LARCH_FPU          (0x1 << 0)
 #define KVM_LARCH_LSX          (0x1 << 1)
 #define KVM_LARCH_LASX         (0x1 << 2)
-#define KVM_LARCH_SWCSR_LATEST (0x1 << 3)
-#define KVM_LARCH_HWCSR_USABLE (0x1 << 4)
+#define KVM_LARCH_LBT          (0x1 << 3)
+#define KVM_LARCH_SWCSR_LATEST (0x1 << 4)
+#define KVM_LARCH_HWCSR_USABLE (0x1 << 5)
 
 struct kvm_vcpu_arch {
        /*
@@ -168,6 +169,7 @@ struct kvm_vcpu_arch {
 
        /* FPU state */
        struct loongarch_fpu fpu FPU_ALIGN;
+       struct loongarch_lbt lbt;
 
        /* CSR state */
        struct loongarch_csrs *csr;
@@ -239,6 +241,11 @@ static inline bool kvm_guest_has_lasx(struct kvm_vcpu_arch *arch)
        return arch->cpucfg[2] & CPUCFG2_LASX;
 }
 
+static inline bool kvm_guest_has_lbt(struct kvm_vcpu_arch *arch)
+{
+       return arch->cpucfg[2] & (CPUCFG2_X86BT | CPUCFG2_ARMBT | CPUCFG2_MIPSBT);
+}
+
 /* Debug: dump vcpu state */
 int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
 

diff --git a/arch/loongarch/include/asm/kvm_vcpu.h b/arch/loongarch/include/asm/kvm_vcpu.h
index 8657008..ca067bf 100644 (file)
--- a/arch/loongarch/include/asm/kvm_vcpu.h
+++ b/arch/loongarch/include/asm/kvm_vcpu.h
@@ -75,6 +75,12 @@ static inline void kvm_save_lasx(struct loongarch_fpu *fpu) { }
 static inline void kvm_restore_lasx(struct loongarch_fpu *fpu) { }
 #endif
 
+#ifdef CONFIG_CPU_HAS_LBT
+int kvm_own_lbt(struct kvm_vcpu *vcpu);
+#else
+static inline int kvm_own_lbt(struct kvm_vcpu *vcpu) { return -EINVAL; }
+#endif
+
 void kvm_init_timer(struct kvm_vcpu *vcpu, unsigned long hz);
 void kvm_save_timer(struct kvm_vcpu *vcpu);
 void kvm_restore_timer(struct kvm_vcpu *vcpu);

diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index ea73f9d..a3d550a 100644 (file)
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -748,6 +748,14 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu)
        return RESUME_GUEST;
 }
 
+static int kvm_handle_lbt_disabled(struct kvm_vcpu *vcpu)
+{
+       if (kvm_own_lbt(vcpu))
+               kvm_queue_exception(vcpu, EXCCODE_INE, 0);
+
+       return RESUME_GUEST;
+}
+
 static int kvm_send_pv_ipi(struct kvm_vcpu *vcpu)
 {
        unsigned int min, cpu, i;
@@ -865,6 +873,7 @@ static exit_handle_fn kvm_fault_tables[EXCCODE_INT_START] = {
        [EXCCODE_FPDIS]                 = kvm_handle_fpu_disabled,
        [EXCCODE_LSXDIS]                = kvm_handle_lsx_disabled,
        [EXCCODE_LASXDIS]               = kvm_handle_lasx_disabled,
+       [EXCCODE_BTDIS]                 = kvm_handle_lbt_disabled,
        [EXCCODE_GSPR]                  = kvm_handle_gspr,
        [EXCCODE_HVC]                   = kvm_handle_hypercall,
 };

diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index ae991b3..8b45f6a 100644 (file)
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -6,6 +6,7 @@
 #include <linux/kvm_host.h>
 #include <linux/entry-kvm.h>
 #include <asm/fpu.h>
+#include <asm/lbt.h>
 #include <asm/loongarch.h>
 #include <asm/setup.h>
 #include <asm/time.h>
@@ -983,12 +984,66 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
        return 0;
 }
 
+#ifdef CONFIG_CPU_HAS_LBT
+int kvm_own_lbt(struct kvm_vcpu *vcpu)
+{
+       if (!kvm_guest_has_lbt(&vcpu->arch))
+               return -EINVAL;
+
+       preempt_disable();
+       set_csr_euen(CSR_EUEN_LBTEN);
+       _restore_lbt(&vcpu->arch.lbt);
+       vcpu->arch.aux_inuse |= KVM_LARCH_LBT;
+       preempt_enable();
+
+       return 0;
+}
+
+static void kvm_lose_lbt(struct kvm_vcpu *vcpu)
+{
+       preempt_disable();
+       if (vcpu->arch.aux_inuse & KVM_LARCH_LBT) {
+               _save_lbt(&vcpu->arch.lbt);
+               clear_csr_euen(CSR_EUEN_LBTEN);
+               vcpu->arch.aux_inuse &= ~KVM_LARCH_LBT;
+       }
+       preempt_enable();
+}
+
+static void kvm_check_fcsr(struct kvm_vcpu *vcpu, unsigned long fcsr)
+{
+       /*
+        * If TM is enabled, top register save/restore will
+        * cause lbt exception, here enable lbt in advance
+        */
+       if (fcsr & FPU_CSR_TM)
+               kvm_own_lbt(vcpu);
+}
+
+static void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu)
+{
+       if (vcpu->arch.aux_inuse & KVM_LARCH_FPU) {
+               if (vcpu->arch.aux_inuse & KVM_LARCH_LBT)
+                       return;
+               kvm_check_fcsr(vcpu, read_fcsr(LOONGARCH_FCSR0));
+       }
+}
+#else
+static inline void kvm_lose_lbt(struct kvm_vcpu *vcpu) { }
+static inline void kvm_check_fcsr(struct kvm_vcpu *vcpu, unsigned long fcsr) { }
+static inline void kvm_check_fcsr_alive(struct kvm_vcpu *vcpu) { }
+#endif
+
 /* Enable FPU and restore context */
 void kvm_own_fpu(struct kvm_vcpu *vcpu)
 {
        preempt_disable();
 
-       /* Enable FPU */
+       /*
+        * Enable FPU for guest
+        * Set FR and FRE according to guest context
+        */
+       kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
        set_csr_euen(CSR_EUEN_FPEN);
 
        kvm_restore_fpu(&vcpu->arch.fpu);
@@ -1008,6 +1063,7 @@ int kvm_own_lsx(struct kvm_vcpu *vcpu)
        preempt_disable();
 
        /* Enable LSX for guest */
+       kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
        set_csr_euen(CSR_EUEN_LSXEN | CSR_EUEN_FPEN);
        switch (vcpu->arch.aux_inuse & KVM_LARCH_FPU) {
        case KVM_LARCH_FPU:
@@ -1042,6 +1098,7 @@ int kvm_own_lasx(struct kvm_vcpu *vcpu)
 
        preempt_disable();
 
+       kvm_check_fcsr(vcpu, vcpu->arch.fpu.fcsr);
        set_csr_euen(CSR_EUEN_FPEN | CSR_EUEN_LSXEN | CSR_EUEN_LASXEN);
        switch (vcpu->arch.aux_inuse & (KVM_LARCH_FPU | KVM_LARCH_LSX)) {
        case KVM_LARCH_LSX:
@@ -1073,6 +1130,7 @@ void kvm_lose_fpu(struct kvm_vcpu *vcpu)
 {
        preempt_disable();
 
+       kvm_check_fcsr_alive(vcpu);
        if (vcpu->arch.aux_inuse & KVM_LARCH_LASX) {
                kvm_save_lasx(&vcpu->arch.fpu);
                vcpu->arch.aux_inuse &= ~(KVM_LARCH_LSX | KVM_LARCH_FPU | KVM_LARCH_LASX);
@@ -1095,6 +1153,7 @@ void kvm_lose_fpu(struct kvm_vcpu *vcpu)
                /* Disable FPU */
                clear_csr_euen(CSR_EUEN_FPEN);
        }
+       kvm_lose_lbt(vcpu);
 
        preempt_enable();
 }