[RFC PATCH 10/14] RISC-V: KVM: Add support for SBI STA registers

Andrew Jones
2023-04-17T11:45:37Z

KVM userspace needs to be able to save and restore the steal-time
shared memory address. Provide the address through the get/set-one-reg
interface with two ulong-sized SBI STA extension registers (lo and hi).
64-bit KVM will always save/restore zero for the hi register.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
arch/riscv/include/asm/kvm_vcpu_sbi.h | 4 +++
arch/riscv/include/uapi/asm/kvm.h | 10 ++++++
arch/riscv/kvm/vcpu.c | 5 +++
arch/riscv/kvm/vcpu_sbi_sta.c | 52 +++++++++++++++++++++++++++
4 files changed, 71 insertions(+)

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index c63c6bbc2f74..ed5a294c479a 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -52,6 +52,10 @@ int kvm_riscv_vcpu_get_reg_sbi_ext(struct kvm_vcpu *vcpu,
const struct kvm_one_reg *reg);
const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
struct kvm_vcpu *vcpu, unsigned long extid);
+int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
+ unsigned long *reg_val);
+int kvm_riscv_vcpu_set_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
+ unsigned long reg_val);
int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);

#ifdef CONFIG_RISCV_SBI_V01
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 172dc565e01a..17b109a9ba7b 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -128,6 +128,12 @@ enum KVM_RISCV_SBI_EXT_ID {
KVM_RISCV_SBI_EXT_MAX,
};

+/* SBI STA extension registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
+struct kvm_riscv_sbi_sta {
+ unsigned long shmem_lo;
+ unsigned long shmem_hi;
+};
+
/* Possible states for kvm_riscv_timer */
#define KVM_RISCV_TIMER_STATE_OFF 0
#define KVM_RISCV_TIMER_STATE_ON 1
@@ -189,6 +195,10 @@ enum KVM_RISCV_SBI_EXT_ID {
/* Registers for specific SBI extensions are mapped as type 9 */
#define KVM_REG_RISCV_SBI (0x09 << KVM_REG_RISCV_TYPE_SHIFT)

+#define KVM_REG_RISCV_SBI_STA (0x1 << KVM_REG_RISCV_SUBTYPE_SHIFT)
+#define KVM_REG_RISCV_SBI_STA_REG(name) \
+ (offsetof(struct kvm_riscv_sbi_sta, name) / sizeof(unsigned long))
+
#endif

#endif /* __LINUX_KVM_RISCV_H */
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 56aec4c2521e..bdc14ebf50a3 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -603,6 +603,9 @@ static int kvm_riscv_vcpu_get_reg_sbi(struct kvm_vcpu *vcpu,
reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;

switch (reg_subtype) {
+ case KVM_REG_RISCV_SBI_STA:
+ ret = kvm_riscv_vcpu_get_reg_sbi_sta(vcpu, reg_num, &reg_val);
+ break;
default:
return -EINVAL;
}
@@ -636,6 +639,8 @@ static int kvm_riscv_vcpu_set_reg_sbi(struct kvm_vcpu *vcpu,
reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;

switch (reg_subtype) {
+ case KVM_REG_RISCV_SBI_STA:
+ return kvm_riscv_vcpu_set_reg_sbi_sta(vcpu, reg_num, reg_val);
default:
return -EINVAL;
}
diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
index bc4f7390a9a8..3d98f140bd06 100644
--- a/arch/riscv/kvm/vcpu_sbi_sta.c
+++ b/arch/riscv/kvm/vcpu_sbi_sta.c
@@ -3,6 +3,7 @@
* Copyright (c) 2023 Ventana Micro Systems Inc.
*/

+#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/kvm_host.h>
#include <linux/mm.h>
@@ -145,3 +146,54 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
.handler = kvm_sbi_ext_sta_handler,
.probe = kvm_sbi_ext_sta_probe,
};
+
+int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu,
+ unsigned long reg_num,
+ unsigned long *reg_val)
+{
+ switch (reg_num) {
+ case KVM_REG_RISCV_SBI_STA_REG(shmem_lo):
+ *reg_val = (unsigned long)vcpu->arch.sta.shmem;
+ break;
+ case KVM_REG_RISCV_SBI_STA_REG(shmem_hi):
+ if (IS_ENABLED(CONFIG_32BIT))
+ *reg_val = upper_32_bits(vcpu->arch.sta.shmem);
+ else
+ *reg_val = 0;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_set_reg_sbi_sta(struct kvm_vcpu *vcpu,
+ unsigned long reg_num,
+ unsigned long reg_val)
+{
+ switch (reg_num) {
+ case KVM_REG_RISCV_SBI_STA_REG(shmem_lo):
+ if (IS_ENABLED(CONFIG_32BIT)) {
+ gpa_t hi = upper_32_bits(vcpu->arch.sta.shmem);
+
+ vcpu->arch.sta.shmem = reg_val;
+ vcpu->arch.sta.shmem |= hi << 32;
+ } else
+ vcpu->arch.sta.shmem = reg_val;
+ break;
+ case KVM_REG_RISCV_SBI_STA_REG(shmem_hi):
+ if (IS_ENABLED(CONFIG_32BIT)) {
+ gpa_t lo = lower_32_bits(vcpu->arch.sta.shmem);
+
+ vcpu->arch.sta.shmem = ((gpa_t)reg_val << 32);
+ vcpu->arch.sta.shmem |= lo;
+ } else if (reg_val != 0)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
--
2.39.2