[PATCH v1 10/14] RISC-V: KVM: Implement SBI STA extension

Andrew Jones
2023-12-05T18:11:50Z

Add a select SCHED_INFO to the KVM config in order to get run_delay
info. Then implement SBI STA's set-steal-time-shmem function and
kvm_riscv_vcpu_record_steal_time() to provide the steal-time info
to guests.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/vcpu_sbi_sta.c | 96 ++++++++++++++++++++++++++++++++++-
2 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index dfc237d7875b..148e52b516cf 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -32,6 +32,7 @@ config KVM
select KVM_XFER_TO_GUEST_WORK
select MMU_NOTIFIER
select PREEMPT_NOTIFIERS
+ select SCHED_INFO
help
Support hosting virtualized guest machines.

diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
index 073bc47013b7..8b8dbee5500a 100644
--- a/arch/riscv/kvm/vcpu_sbi_sta.c
+++ b/arch/riscv/kvm/vcpu_sbi_sta.c
@@ -6,21 +6,113 @@
#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/kvm_host.h>
+#include <linux/mm.h>
+#include <linux/sizes.h>

+#include <asm/bug.h>
+#include <asm/current.h>
#include <asm/kvm_vcpu_sbi.h>
+#include <asm/page.h>
#include <asm/sbi.h>
+#include <asm/uaccess.h>

void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu)
{
gpa_t shmem = vcpu->arch.sta.shmem;
+ u64 last_steal = vcpu->arch.sta.last_steal;
+ u32 *sequence_ptr, sequence;
+ u64 *steal_ptr, steal;
+ unsigned long hva;
+ gfn_t gfn;

if (shmem == INVALID_GPA)
return;
+
+ /*
+ * shmem is 64-byte aligned (see the enforcement in
+ * kvm_sbi_sta_steal_time_set_shmem()) and the size of sbi_sta_struct
+ * is 64 bytes, so we know all its offsets are in the same page.
+ */
+ gfn = shmem >> PAGE_SHIFT;
+ hva = kvm_vcpu_gfn_to_hva(vcpu, gfn);
+
+ if (WARN_ON(kvm_is_error_hva(hva))) {
+ vcpu->arch.sta.shmem = INVALID_GPA;
+ return;
+ }
+
+ sequence_ptr = (u32 *)(hva + offset_in_page(shmem) +
+ offsetof(struct sbi_sta_struct, sequence));
+ steal_ptr = (u64 *)(hva + offset_in_page(shmem) +
+ offsetof(struct sbi_sta_struct, steal));
+
+ if (WARN_ON(get_user(sequence, sequence_ptr)))
+ return;
+
+ sequence = le32_to_cpu(sequence);
+ sequence += 1;
+
+ if (WARN_ON(put_user(cpu_to_le32(sequence), sequence_ptr)))
+ return;
+
+ if (!WARN_ON(get_user(steal, steal_ptr))) {
+ steal = le64_to_cpu(steal);
+ vcpu->arch.sta.last_steal = READ_ONCE(current->sched_info.run_delay);
+ steal += vcpu->arch.sta.last_steal - last_steal;
+ WARN_ON(put_user(cpu_to_le64(steal), steal_ptr));
+ }
+
+ sequence += 1;
+ WARN_ON(put_user(cpu_to_le32(sequence), sequence_ptr));
+
+ kvm_vcpu_mark_page_dirty(vcpu, gfn);
}

static int kvm_sbi_sta_steal_time_set_shmem(struct kvm_vcpu *vcpu)
{
- return SBI_ERR_FAILURE;
+ struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+ unsigned long shmem_phys_lo = cp->a0;
+ unsigned long shmem_phys_hi = cp->a1;
+ u32 flags = cp->a2;
+ struct sbi_sta_struct zero_sta = {0};
+ unsigned long hva;
+ bool writable;
+ gpa_t shmem;
+ int ret;
+
+ if (flags != 0)
+ return SBI_ERR_INVALID_PARAM;
+
+ if (shmem_phys_lo == SBI_STA_SHMEM_DISABLE &&
+ shmem_phys_hi == SBI_STA_SHMEM_DISABLE) {
+ vcpu->arch.sta.shmem = INVALID_GPA;
+ return 0;
+ }
+
+ if (shmem_phys_lo & (SZ_64 - 1))
+ return SBI_ERR_INVALID_PARAM;
+
+ shmem = shmem_phys_lo;
+
+ if (shmem_phys_hi != 0) {
+ if (IS_ENABLED(CONFIG_32BIT))
+ shmem |= ((gpa_t)shmem_phys_hi << 32);
+ else
+ return SBI_ERR_INVALID_ADDRESS;
+ }
+
+ hva = kvm_vcpu_gfn_to_hva_prot(vcpu, shmem >> PAGE_SHIFT, &writable);
+ if (kvm_is_error_hva(hva) || !writable)
+ return SBI_ERR_INVALID_ADDRESS;
+
+ ret = kvm_vcpu_write_guest(vcpu, shmem, &zero_sta, sizeof(zero_sta));
+ if (ret)
+ return SBI_ERR_FAILURE;
+
+ vcpu->arch.sta.shmem = shmem;
+ vcpu->arch.sta.last_steal = current->sched_info.run_delay;
+
+ return 0;
}

static int kvm_sbi_ext_sta_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
@@ -46,7 +138,7 @@ static int kvm_sbi_ext_sta_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,

static unsigned long kvm_sbi_ext_sta_probe(struct kvm_vcpu *vcpu)
{
- return 0;
+ return !!sched_info_on();
}

const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {