RISC-V: KVM: Add support for Svpbmt inside Guest/VM

The Guest/VM can use Svpbmt in VS-stage page tables when allowed by the
Hypervisor using the henvcfg.PBMTE bit.

We add Svpbmt support for the KVM Guest/VM which can be enabled/disabled
by the KVM user-space (QEMU/KVMTOOL) using the ISA extension ONE_REG
interface.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/csr.h

@@ -156,6 +156,18 @@
 				 (_AC(1, UL) << IRQ_S_TIMER) | \
 				 (_AC(1, UL) << IRQ_S_EXT))
 
+/* xENVCFG flags */
+#define ENVCFG_STCE			(_AC(1, ULL) << 63)
+#define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
+#define ENVCFG_CBZE			(_AC(1, UL) << 7)
+#define ENVCFG_CBCFE			(_AC(1, UL) << 6)
+#define ENVCFG_CBIE_SHIFT		4
+#define ENVCFG_CBIE			(_AC(0x3, UL) << ENVCFG_CBIE_SHIFT)
+#define ENVCFG_CBIE_ILL			_AC(0x0, UL)
+#define ENVCFG_CBIE_FLUSH		_AC(0x1, UL)
+#define ENVCFG_CBIE_INV			_AC(0x3, UL)
+#define ENVCFG_FIOM			_AC(0x1, UL)
+
 /* symbolic CSR names: */
 #define CSR_CYCLE		0xc00
 #define CSR_TIME		0xc01
@@ -252,7 +264,9 @@
 #define CSR_HTIMEDELTA		0x605
 #define CSR_HCOUNTEREN		0x606
 #define CSR_HGEIE		0x607
+#define CSR_HENVCFG		0x60a
 #define CSR_HTIMEDELTAH		0x615
+#define CSR_HENVCFGH		0x61a
 #define CSR_HTVAL		0x643
 #define CSR_HIP			0x644
 #define CSR_HVIP		0x645
@@ -264,6 +278,8 @@
 #define CSR_MISA		0x301
 #define CSR_MIE			0x304
 #define CSR_MTVEC		0x305
+#define CSR_MENVCFG		0x30a
+#define CSR_MENVCFGH		0x31a
 #define CSR_MSCRATCH		0x340
 #define CSR_MEPC		0x341
 #define CSR_MCAUSE		0x342

arch/riscv/include/uapi/asm/kvm.h

@@ -96,6 +96,7 @@ enum KVM_RISCV_ISA_EXT_ID {
 	KVM_RISCV_ISA_EXT_H,
 	KVM_RISCV_ISA_EXT_I,
 	KVM_RISCV_ISA_EXT_M,
+	KVM_RISCV_ISA_EXT_SVPBMT,
 	KVM_RISCV_ISA_EXT_MAX,
 };
 

arch/riscv/kvm/vcpu.c

@@ -51,6 +51,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
 	RISCV_ISA_EXT_h,
 	RISCV_ISA_EXT_i,
 	RISCV_ISA_EXT_m,
+	RISCV_ISA_EXT_SVPBMT,
 };
 
 static unsigned long kvm_riscv_vcpu_base2isa_ext(unsigned long base_ext)
@@ -777,6 +778,19 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 	return -EINVAL;
 }
 
+static void kvm_riscv_vcpu_update_config(const unsigned long *isa)
+{
+	u64 henvcfg = 0;
+
+	if (__riscv_isa_extension_available(isa, RISCV_ISA_EXT_SVPBMT))
+		henvcfg |= ENVCFG_PBMTE;
+
+	csr_write(CSR_HENVCFG, henvcfg);
+#ifdef CONFIG_32BIT
+	csr_write(CSR_HENVCFGH, henvcfg >> 32);
+#endif
+}
+
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
@@ -791,6 +805,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	csr_write(CSR_HVIP, csr->hvip);
 	csr_write(CSR_VSATP, csr->vsatp);
 
+	kvm_riscv_vcpu_update_config(vcpu->arch.isa);
+
 	kvm_riscv_gstage_update_hgatp(vcpu);
 
 	kvm_riscv_vcpu_timer_restore(vcpu);