[PATCH RFC 08/11] riscv: KVM: Add Sdtrig Extension Support for Guest/VM

From: Max Hsu
Date: Fri Mar 29 2024 - 05:31:06 EST

From: Yong-Xuan Wang <yongxuan.wang@xxxxxxxxxx>

We extend the KVM ISA extension ONE_REG interface to allow VMM
tools to detect and enable Sdtrig extension for Guest/VM. We
also save/restore the scontext CSR for guest VCPUs and set the
HSCONTEXT bit in hstateen0 CSR if the scontext CSR is available
for Guest/VM when the Smstateen extension is present.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@xxxxxxxxxx>
Co-developed-by: Max Hsu <max.hsu@xxxxxxxxxx>
Signed-off-by: Max Hsu <max.hsu@xxxxxxxxxx>
---
arch/riscv/include/asm/kvm_host.h | 11 +++++++++++
arch/riscv/include/asm/kvm_vcpu_debug.h | 17 +++++++++++++++++
arch/riscv/include/uapi/asm/kvm.h | 1 +
arch/riscv/kvm/Makefile | 1 +
arch/riscv/kvm/vcpu.c | 8 ++++++++
arch/riscv/kvm/vcpu_debug.c | 29 +++++++++++++++++++++++++++++
arch/riscv/kvm/vcpu_onereg.c | 1 +
7 files changed, 68 insertions(+)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 484d04a92fa6..d495279d99e1 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -21,6 +21,7 @@
#include <asm/kvm_vcpu_sbi.h>
#include <asm/kvm_vcpu_timer.h>
#include <asm/kvm_vcpu_pmu.h>
+#include <asm/kvm_vcpu_debug.h>

#define KVM_MAX_VCPUS 1024

@@ -175,6 +176,10 @@ struct kvm_vcpu_smstateen_csr {
unsigned long sstateen0;
};

+struct kvm_vcpu_sdtrig_csr {
+ unsigned long scontext;
+};
+
struct kvm_vcpu_arch {
/* VCPU ran at least once */
bool ran_atleast_once;
@@ -197,6 +202,9 @@ struct kvm_vcpu_arch {
unsigned long host_senvcfg;
unsigned long host_sstateen0;

+ /* SCONTEXT of Host */
+ unsigned long host_scontext;
+
/* CPU context of Host */
struct kvm_cpu_context host_context;

@@ -209,6 +217,9 @@ struct kvm_vcpu_arch {
/* CPU Smstateen CSR context of Guest VCPU */
struct kvm_vcpu_smstateen_csr smstateen_csr;

+ /* CPU Sdtrig CSR context of Guest VCPU */
+ struct kvm_vcpu_sdtrig_csr sdtrig_csr;
+
/* CPU context upon Guest VCPU reset */
struct kvm_cpu_context guest_reset_context;

diff --git a/arch/riscv/include/asm/kvm_vcpu_debug.h b/arch/riscv/include/asm/kvm_vcpu_debug.h
new file mode 100644
index 000000000000..6e7ce6b408a6
--- /dev/null
+++ b/arch/riscv/include/asm/kvm_vcpu_debug.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 SiFive
+ *
+ * Authors:
+ * Yong-Xuan Wang <yongxuan.wang@xxxxxxxxxx>
+ */
+
+#ifndef __KVM_VCPU_RISCV_DEBUG_H
+#define __KVM_VCPU_RISCV_DEBUG_H
+
+#include <linux/types.h>
+
+void kvm_riscv_debug_vcpu_swap_in_guest_context(struct kvm_vcpu *vcpu);
+void kvm_riscv_debug_vcpu_swap_in_host_context(struct kvm_vcpu *vcpu);
+
+#endif
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index b1c503c2959c..9f70da85ed51 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -167,6 +167,7 @@ enum KVM_RISCV_ISA_EXT_ID {
KVM_RISCV_ISA_EXT_ZFA,
KVM_RISCV_ISA_EXT_ZTSO,
KVM_RISCV_ISA_EXT_ZACAS,
+ KVM_RISCV_ISA_EXT_SDTRIG,
KVM_RISCV_ISA_EXT_MAX,
};

diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index c9646521f113..387be968d9ea 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -15,6 +15,7 @@ kvm-y += vmid.o
kvm-y += tlb.o
kvm-y += mmu.o
kvm-y += vcpu.o
+kvm-y += vcpu_debug.o
kvm-y += vcpu_exit.o
kvm-y += vcpu_fp.o
kvm-y += vcpu_vector.o
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index b5ca9f2e98ac..1d0e43ab0652 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -20,6 +20,7 @@
#include <asm/csr.h>
#include <asm/cacheflush.h>
#include <asm/kvm_vcpu_vector.h>
+#include <asm/switch_to.h>

const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
KVM_GENERIC_VCPU_STATS(),
@@ -504,6 +505,9 @@ static void kvm_riscv_vcpu_setup_config(struct kvm_vcpu *vcpu)
SMSTATEEN0_AIA_ISEL;
if (riscv_isa_extension_available(isa, SMSTATEEN))
cfg->hstateen0 |= SMSTATEEN0_SSTATEEN0;
+
+ if (has_scontext())
+ cfg->hstateen0 |= SMSTATEEN0_HSCONTEXT;
}
}

@@ -643,6 +647,8 @@ static __always_inline void kvm_riscv_vcpu_swap_in_guest_state(struct kvm_vcpu *
(cfg->hstateen0 & SMSTATEEN0_SSTATEEN0))
vcpu->arch.host_sstateen0 = csr_swap(CSR_SSTATEEN0,
smcsr->sstateen0);
+
+ kvm_riscv_debug_vcpu_swap_in_guest_context(vcpu);
}

static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *vcpu)
@@ -656,6 +662,8 @@ static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *v
(cfg->hstateen0 & SMSTATEEN0_SSTATEEN0))
smcsr->sstateen0 = csr_swap(CSR_SSTATEEN0,
vcpu->arch.host_sstateen0);
+
+ kvm_riscv_debug_vcpu_swap_in_host_context(vcpu);
}

/*
diff --git a/arch/riscv/kvm/vcpu_debug.c b/arch/riscv/kvm/vcpu_debug.c
new file mode 100644
index 000000000000..e7e9263c2e30
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_debug.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 SiFive
+ */
+
+#include <linux/kvm_host.h>
+#include <asm/switch_to.h>
+
+void kvm_riscv_debug_vcpu_swap_in_guest_context(struct kvm_vcpu *vcpu)
+{
+ struct kvm_vcpu_sdtrig_csr *csr = &vcpu->arch.sdtrig_csr;
+ unsigned long hcontext = vcpu->kvm->arch.hcontext;
+
+ if (has_hcontext())
+ csr_write(CSR_HCONTEXT, hcontext);
+ if (has_scontext())
+ vcpu->arch.host_scontext = csr_swap(CSR_SCONTEXT, csr->scontext);
+}
+
+void kvm_riscv_debug_vcpu_swap_in_host_context(struct kvm_vcpu *vcpu)
+{
+ struct kvm_vcpu_sdtrig_csr *csr = &vcpu->arch.sdtrig_csr;
+
+ /* Hypervisor uses the hcontext ID 0 */
+ if (has_hcontext())
+ csr_write(CSR_HCONTEXT, 0);
+ if (has_scontext())
+ csr->scontext = csr_swap(CSR_SCONTEXT, vcpu->arch.host_scontext);
+}
diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index f4a6124d25c9..10dda5ddc0a6 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -34,6 +34,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
[KVM_RISCV_ISA_EXT_M] = RISCV_ISA_EXT_m,
[KVM_RISCV_ISA_EXT_V] = RISCV_ISA_EXT_v,
/* Multi letter extensions (alphabetically sorted) */
+ KVM_ISA_EXT_ARR(SDTRIG),
KVM_ISA_EXT_ARR(SMSTATEEN),
KVM_ISA_EXT_ARR(SSAIA),
KVM_ISA_EXT_ARR(SSTC),

--
2.43.2