Re: [PATCH 09/13] RISC-V: KVM: Use nacl_csr_xyz() for accessing H-extension CSRs

Atish Patra
2024-10-18T19:31:38Z

On Fri, Jul 19, 2024 at 9:09 AM Anup Patel <apatel@ventanamicro.com> wrote:
>
> When running under some other hypervisor, prefer nacl_csr_xyz()
> for accessing H-extension CSRs in the run-loop. This makes CSR
> access faster whenever SBI nested acceleration is available.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/kvm/mmu.c | 4 +-
> arch/riscv/kvm/vcpu.c | 103 +++++++++++++++++++++++++-----------
> arch/riscv/kvm/vcpu_timer.c | 28 +++++-----
> 3 files changed, 87 insertions(+), 48 deletions(-)
>
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index b63650f9b966..45ace9138947 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -15,7 +15,7 @@
> #include <linux/vmalloc.h>
> #include <linux/kvm_host.h>
> #include <linux/sched/signal.h>
> -#include <asm/csr.h>
> +#include <asm/kvm_nacl.h>
> #include <asm/page.h>
> #include <asm/pgtable.h>
>
> @@ -732,7 +732,7 @@ void kvm_riscv_gstage_update_hgatp(struct kvm_vcpu *vcpu)
> hgatp |= (READ_ONCE(k->vmid.vmid) << HGATP_VMID_SHIFT) & HGATP_VMID;
> hgatp |= (k->pgd_phys >> PAGE_SHIFT) & HGATP_PPN;
>
> - csr_write(CSR_HGATP, hgatp);
> + ncsr_write(CSR_HGATP, hgatp);
>
> if (!kvm_riscv_gstage_vmid_bits())
> kvm_riscv_local_hfence_gvma_all();
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 957e1a5e081b..00baaf1b0136 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -17,8 +17,8 @@
> #include <linux/sched/signal.h>
> #include <linux/fs.h>
> #include <linux/kvm_host.h>
> -#include <asm/csr.h>
> #include <asm/cacheflush.h>
> +#include <asm/kvm_nacl.h>
> #include <asm/kvm_vcpu_vector.h>
>
> #define CREATE_TRACE_POINTS
> @@ -361,10 +361,10 @@ void kvm_riscv_vcpu_sync_interrupts(struct kvm_vcpu *vcpu)
> struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
>
> /* Read current HVIP and VSIE CSRs */
> - csr->vsie = csr_read(CSR_VSIE);
> + csr->vsie = ncsr_read(CSR_VSIE);
>
> /* Sync-up HVIP.VSSIP bit changes does by Guest */
> - hvip = csr_read(CSR_HVIP);
> + hvip = ncsr_read(CSR_HVIP);
> if ((csr->hvip ^ hvip) & (1UL << IRQ_VS_SOFT)) {
> if (hvip & (1UL << IRQ_VS_SOFT)) {
> if (!test_and_set_bit(IRQ_VS_SOFT,
> @@ -561,26 +561,49 @@ static void kvm_riscv_vcpu_setup_config(struct kvm_vcpu *vcpu)
>
> void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> {
> + void *nsh;
> struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
> struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
>
> - csr_write(CSR_VSSTATUS, csr->vsstatus);
> - csr_write(CSR_VSIE, csr->vsie);
> - csr_write(CSR_VSTVEC, csr->vstvec);
> - csr_write(CSR_VSSCRATCH, csr->vsscratch);
> - csr_write(CSR_VSEPC, csr->vsepc);
> - csr_write(CSR_VSCAUSE, csr->vscause);
> - csr_write(CSR_VSTVAL, csr->vstval);
> - csr_write(CSR_HEDELEG, cfg->hedeleg);
> - csr_write(CSR_HVIP, csr->hvip);
> - csr_write(CSR_VSATP, csr->vsatp);
> - csr_write(CSR_HENVCFG, cfg->henvcfg);
> - if (IS_ENABLED(CONFIG_32BIT))
> - csr_write(CSR_HENVCFGH, cfg->henvcfg >> 32);
> - if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN)) {
> - csr_write(CSR_HSTATEEN0, cfg->hstateen0);
> + if (kvm_riscv_nacl_sync_csr_available()) {
> + nsh = nacl_shmem();
> + nacl_csr_write(nsh, CSR_VSSTATUS, csr->vsstatus);
> + nacl_csr_write(nsh, CSR_VSIE, csr->vsie);
> + nacl_csr_write(nsh, CSR_VSTVEC, csr->vstvec);
> + nacl_csr_write(nsh, CSR_VSSCRATCH, csr->vsscratch);
> + nacl_csr_write(nsh, CSR_VSEPC, csr->vsepc);
> + nacl_csr_write(nsh, CSR_VSCAUSE, csr->vscause);
> + nacl_csr_write(nsh, CSR_VSTVAL, csr->vstval);
> + nacl_csr_write(nsh, CSR_HEDELEG, cfg->hedeleg);
> + nacl_csr_write(nsh, CSR_HVIP, csr->hvip);
> + nacl_csr_write(nsh, CSR_VSATP, csr->vsatp);
> + nacl_csr_write(nsh, CSR_HENVCFG, cfg->henvcfg);
> + if (IS_ENABLED(CONFIG_32BIT))
> + nacl_csr_write(nsh, CSR_HENVCFGH, cfg->henvcfg >> 32);
> + if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN)) {
> + nacl_csr_write(nsh, CSR_HSTATEEN0, cfg->hstateen0);
> + if (IS_ENABLED(CONFIG_32BIT))
> + nacl_csr_write(nsh, CSR_HSTATEEN0H, cfg->hstateen0 >> 32);
> + }
> + } else {
> + csr_write(CSR_VSSTATUS, csr->vsstatus);
> + csr_write(CSR_VSIE, csr->vsie);
> + csr_write(CSR_VSTVEC, csr->vstvec);
> + csr_write(CSR_VSSCRATCH, csr->vsscratch);
> + csr_write(CSR_VSEPC, csr->vsepc);
> + csr_write(CSR_VSCAUSE, csr->vscause);
> + csr_write(CSR_VSTVAL, csr->vstval);
> + csr_write(CSR_HEDELEG, cfg->hedeleg);
> + csr_write(CSR_HVIP, csr->hvip);
> + csr_write(CSR_VSATP, csr->vsatp);
> + csr_write(CSR_HENVCFG, cfg->henvcfg);
> if (IS_ENABLED(CONFIG_32BIT))
> - csr_write(CSR_HSTATEEN0H, cfg->hstateen0 >> 32);
> + csr_write(CSR_HENVCFGH, cfg->henvcfg >> 32);
> + if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN)) {
> + csr_write(CSR_HSTATEEN0, cfg->hstateen0);
> + if (IS_ENABLED(CONFIG_32BIT))
> + csr_write(CSR_HSTATEEN0H, cfg->hstateen0 >> 32);
> + }
> }
>
> kvm_riscv_gstage_update_hgatp(vcpu);
> @@ -603,6 +626,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>
> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> {
> + void *nsh;
> struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
>
> vcpu->cpu = -1;
> @@ -618,15 +642,28 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> vcpu->arch.isa);
> kvm_riscv_vcpu_host_vector_restore(&vcpu->arch.host_context);
>
> - csr->vsstatus = csr_read(CSR_VSSTATUS);
> - csr->vsie = csr_read(CSR_VSIE);
> - csr->vstvec = csr_read(CSR_VSTVEC);
> - csr->vsscratch = csr_read(CSR_VSSCRATCH);
> - csr->vsepc = csr_read(CSR_VSEPC);
> - csr->vscause = csr_read(CSR_VSCAUSE);
> - csr->vstval = csr_read(CSR_VSTVAL);
> - csr->hvip = csr_read(CSR_HVIP);
> - csr->vsatp = csr_read(CSR_VSATP);
> + if (kvm_riscv_nacl_available()) {

Should we leave a comment here why ncsr_read is not efficient here
i.e. due to block access ?

> + nsh = nacl_shmem();
> + csr->vsstatus = nacl_csr_read(nsh, CSR_VSSTATUS);
> + csr->vsie = nacl_csr_read(nsh, CSR_VSIE);
> + csr->vstvec = nacl_csr_read(nsh, CSR_VSTVEC);
> + csr->vsscratch = nacl_csr_read(nsh, CSR_VSSCRATCH);
> + csr->vsepc = nacl_csr_read(nsh, CSR_VSEPC);
> + csr->vscause = nacl_csr_read(nsh, CSR_VSCAUSE);
> + csr->vstval = nacl_csr_read(nsh, CSR_VSTVAL);
> + csr->hvip = nacl_csr_read(nsh, CSR_HVIP);
> + csr->vsatp = nacl_csr_read(nsh, CSR_VSATP);
> + } else {
> + csr->vsstatus = csr_read(CSR_VSSTATUS);
> + csr->vsie = csr_read(CSR_VSIE);
> + csr->vstvec = csr_read(CSR_VSTVEC);
> + csr->vsscratch = csr_read(CSR_VSSCRATCH);
> + csr->vsepc = csr_read(CSR_VSEPC);
> + csr->vscause = csr_read(CSR_VSCAUSE);
> + csr->vstval = csr_read(CSR_VSTVAL);
> + csr->hvip = csr_read(CSR_HVIP);
> + csr->vsatp = csr_read(CSR_VSATP);
> + }
> }
>
> static void kvm_riscv_check_vcpu_requests(struct kvm_vcpu *vcpu)
> @@ -681,7 +718,7 @@ static void kvm_riscv_update_hvip(struct kvm_vcpu *vcpu)
> {
> struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
>
> - csr_write(CSR_HVIP, csr->hvip);
> + ncsr_write(CSR_HVIP, csr->hvip);
> kvm_riscv_vcpu_aia_update_hvip(vcpu);
> }
>
> @@ -728,7 +765,9 @@ static void noinstr kvm_riscv_vcpu_enter_exit(struct kvm_vcpu *vcpu)
> kvm_riscv_vcpu_swap_in_guest_state(vcpu);
> guest_state_enter_irqoff();
>
> - hcntx->hstatus = csr_swap(CSR_HSTATUS, gcntx->hstatus);
> + hcntx->hstatus = ncsr_swap(CSR_HSTATUS, gcntx->hstatus);
> +
> + nsync_csr(-1UL);
>
> __kvm_riscv_switch_to(&vcpu->arch);
>
> @@ -863,8 +902,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> trap.sepc = vcpu->arch.guest_context.sepc;
> trap.scause = csr_read(CSR_SCAUSE);
> trap.stval = csr_read(CSR_STVAL);
> - trap.htval = csr_read(CSR_HTVAL);
> - trap.htinst = csr_read(CSR_HTINST);
> + trap.htval = ncsr_read(CSR_HTVAL);
> + trap.htinst = ncsr_read(CSR_HTINST);
>
> /* Syncup interrupts state with HW */
> kvm_riscv_vcpu_sync_interrupts(vcpu);
> diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c
> index 75486b25ac45..96e7a4e463f7 100644
> --- a/arch/riscv/kvm/vcpu_timer.c
> +++ b/arch/riscv/kvm/vcpu_timer.c
> @@ -11,8 +11,8 @@
> #include <linux/kvm_host.h>
> #include <linux/uaccess.h>
> #include <clocksource/timer-riscv.h>
> -#include <asm/csr.h>
> #include <asm/delay.h>
> +#include <asm/kvm_nacl.h>
> #include <asm/kvm_vcpu_timer.h>
>
> static u64 kvm_riscv_current_cycles(struct kvm_guest_timer *gt)
> @@ -72,12 +72,12 @@ static int kvm_riscv_vcpu_timer_cancel(struct kvm_vcpu_timer *t)
> static int kvm_riscv_vcpu_update_vstimecmp(struct kvm_vcpu *vcpu, u64 ncycles)
> {
> #if defined(CONFIG_32BIT)
> - csr_write(CSR_VSTIMECMP, ncycles & 0xFFFFFFFF);
> - csr_write(CSR_VSTIMECMPH, ncycles >> 32);
> + ncsr_write(CSR_VSTIMECMP, ncycles & 0xFFFFFFFF);
> + ncsr_write(CSR_VSTIMECMPH, ncycles >> 32);
> #else
> - csr_write(CSR_VSTIMECMP, ncycles);
> + ncsr_write(CSR_VSTIMECMP, ncycles);
> #endif
> - return 0;
> + return 0;
> }
>
> static int kvm_riscv_vcpu_update_hrtimer(struct kvm_vcpu *vcpu, u64 ncycles)
> @@ -289,10 +289,10 @@ static void kvm_riscv_vcpu_update_timedelta(struct kvm_vcpu *vcpu)
> struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
>
> #if defined(CONFIG_32BIT)
> - csr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
> - csr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
> + ncsr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
> + ncsr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
> #else
> - csr_write(CSR_HTIMEDELTA, gt->time_delta);
> + ncsr_write(CSR_HTIMEDELTA, gt->time_delta);
> #endif
> }
>
> @@ -306,10 +306,10 @@ void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
> return;
>
> #if defined(CONFIG_32BIT)
> - csr_write(CSR_VSTIMECMP, (u32)t->next_cycles);
> - csr_write(CSR_VSTIMECMPH, (u32)(t->next_cycles >> 32));
> + ncsr_write(CSR_VSTIMECMP, (u32)t->next_cycles);
> + ncsr_write(CSR_VSTIMECMPH, (u32)(t->next_cycles >> 32));
> #else
> - csr_write(CSR_VSTIMECMP, t->next_cycles);
> + ncsr_write(CSR_VSTIMECMP, t->next_cycles);
> #endif
>
> /* timer should be enabled for the remaining operations */
> @@ -327,10 +327,10 @@ void kvm_riscv_vcpu_timer_sync(struct kvm_vcpu *vcpu)
> return;
>
> #if defined(CONFIG_32BIT)
> - t->next_cycles = csr_read(CSR_VSTIMECMP);
> - t->next_cycles |= (u64)csr_read(CSR_VSTIMECMPH) << 32;
> + t->next_cycles = ncsr_read(CSR_VSTIMECMP);
> + t->next_cycles |= (u64)ncsr_read(CSR_VSTIMECMPH) << 32;
> #else
> - t->next_cycles = csr_read(CSR_VSTIMECMP);
> + t->next_cycles = ncsr_read(CSR_VSTIMECMP);
> #endif
> }
>
> --
> 2.34.1
>

Otherwise, LGTM.

Reviewed-by: Atish Patra <atishp@rivosinc.com>

--
Regards,
Atish