Re: [PATCH v5 12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature

On Wed, Apr 03, 2024 at 01:04:41AM -0700, Atish Patra wrote:

PMU Snapshot function allows to minimize the number of traps when the guest access configures/access the hpmcounters. If the snapshot feature is enabled, the hypervisor updates the shared memory with counter data and state of overflown counters. The guest can just read the shared memory instead of trap & emulate done by the hypervisor.

This patch doesn't implement the counter overflow yet.

Reviewed-by: Anup Patel anup@brainfault.org Signed-off-by: Atish Patra atishp@rivosinc.com

---

arch/riscv/include/asm/kvm_vcpu_pmu.h | 7 ++ arch/riscv/kvm/vcpu_pmu.c | 121 +++++++++++++++++++++++++- arch/riscv/kvm/vcpu_sbi_pmu.c | 3 + 3 files changed, 130 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h index 395518a1664e..77a1fc4d203d 100644 --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h @@ -50,6 +50,10 @@ struct kvm_pmu { bool init_done; /* Bit map of all the virtual counter used */ DECLARE_BITMAP(pmc_in_use, RISCV_KVM_MAX_COUNTERS);

• /* The address of the counter snapshot area (guest physical address) */
• gpa_t snapshot_addr;
• /* The actual data of the snapshot */
• struct riscv_pmu_snapshot_data *sdata;

}; #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu_context) @@ -85,6 +89,9 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx, struct kvm_vcpu_sbi_return *retdata); void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu); +int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,

• 		      unsigned long saddr_high, unsigned long flags,
  

• 		      struct kvm_vcpu_sbi_return *retdata);
  

void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu); void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu); diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c index 2d9929bbc2c8..f706c688b338 100644 --- a/arch/riscv/kvm/vcpu_pmu.c +++ b/arch/riscv/kvm/vcpu_pmu.c @@ -14,6 +14,7 @@ #include <asm/csr.h> #include <asm/kvm_vcpu_sbi.h> #include <asm/kvm_vcpu_pmu.h> +#include <asm/sbi.h> #include <linux/bitops.h> #define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs) @@ -311,6 +312,80 @@ int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num, return ret; } +static void kvm_pmu_clear_snapshot_area(struct kvm_vcpu *vcpu) +{

• struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
• int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
• if (kvpmu->sdata) {

• if (kvpmu->snapshot_addr != INVALID_GPA) {
  

• 	memset(kvpmu->sdata, 0, snapshot_area_size);
  

• 	kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr,
  

• 			     kvpmu->sdata, snapshot_area_size);
  

• } else {
  

• 	pr_warn("snapshot address invalid\n");
  

• }
  

• kfree(kvpmu->sdata);
  

• kvpmu->sdata = NULL;
  

• }
• kvpmu->snapshot_addr = INVALID_GPA;

+}

+int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,

• 		      unsigned long saddr_high, unsigned long flags,
  

• 		      struct kvm_vcpu_sbi_return *retdata)
  

+{

• struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
• int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
• int sbiret = 0;
• gpa_t saddr;
• unsigned long hva;
• bool writable;
• if (!kvpmu || flags) {

• sbiret = SBI_ERR_INVALID_PARAM;
  

• goto out;
  

• }
• if (saddr_low == SBI_SHMEM_DISABLE && saddr_high == SBI_SHMEM_DISABLE) {

• kvm_pmu_clear_snapshot_area(vcpu);
  

• return 0;
  

• }
• saddr = saddr_low;
• if (saddr_high != 0) {

• if (IS_ENABLED(CONFIG_32BIT))
  

• 	saddr |= ((gpa_t)saddr << 32);
  

saddr |= ((gpa_t)saddr_high << 32)

• else
  

• 	sbiret = SBI_ERR_INVALID_ADDRESS;
  

• goto out;
  

• }

Thanks, drew