Re: [PATCH RFC v4 13/15] target/riscv: Introduce dynamic time frequency for virt machine

> -----Original Message----- > From: Alistair Francis [mailto:alistair23@gmail.com] > Sent: Wednesday, December 9, 2020 6:26 AM > To: Jiangyifei <jiangyifei(a)huawei.com&gt; > Cc: qemu-devel(a)nongnu.org Developers <qemu-devel(a)nongnu.org>; open > list:RISC-V <qemu-riscv(a)nongnu.org>; Zhangxiaofeng (F) > <victor.zhangxiaofeng(a)huawei.com>; Sagar Karandikar > <sagark(a)eecs.berkeley.edu>; open list:Overall <kvm(a)vger.kernel.org>; > libvir-list(a)redhat.com; Bastian Koppelmann > <kbastian(a)mail.uni-paderborn.de>; Anup Patel <anup.patel(a)wdc.com>; > yinyipeng <yinyipeng1(a)huawei.com>; Alistair Francis > <Alistair.Francis(a)wdc.com>; kvm-riscv(a)lists.infradead.org; Palmer Dabbelt > <palmer(a)dabbelt.com>; dengkai (A) <dengkai1(a)huawei.com>; Wubin (H) > <wu.wubin(a)huawei.com>; Zhanghailiang <zhang.zhanghailiang(a)huawei.com&gt; > Subject: Re: [PATCH RFC v4 13/15] target/riscv: Introduce dynamic time > frequency for virt machine > > On Thu, Dec 3, 2020 at 4:57 AM Yifei Jiang <jiangyifei(a)huawei.com&gt; wrote: > > > > Currently, time base frequency was fixed as SIFIVE_CLINT_TIMEBASE_FREQ. > > Here introduce "time-frequency" property to set time base frequency > > dynamically of which default value is still > > SIFIVE_CLINT_TIMEBASE_FREQ. The virt machine uses frequency of the first > cpu to create clint and fdt. > > > > Signed-off-by: Yifei Jiang <jiangyifei(a)huawei.com&gt; > > Signed-off-by: Yipeng Yin <yinyipeng1(a)huawei.com&gt; > > --- > > hw/riscv/virt.c | 18 ++++++++++++++---- > > target/riscv/cpu.c | 3 +++ > > target/riscv/cpu.h | 2 ++ > > 3 files changed, 19 insertions(+), 4 deletions(-) > > > > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c index > > 47b7018193..788a7237b6 100644 > > --- a/hw/riscv/virt.c > > +++ b/hw/riscv/virt.c > > @@ -178,7 +178,7 @@ static void create_pcie_irq_map(void *fdt, char > > *nodename, } > > > > static void create_fdt(RISCVVirtState *s, const struct MemmapEntry > *memmap, > > - uint64_t mem_size, const char *cmdline) > > + uint64_t mem_size, const char *cmdline, uint64_t > > + timebase_frequency) > > { > > void *fdt; > > int i, cpu, socket; > > @@ -225,7 +225,7 @@ static void create_fdt(RISCVVirtState *s, const > > struct MemmapEntry *memmap, > > > > qemu_fdt_add_subnode(fdt, "/cpus"); > > qemu_fdt_setprop_cell(fdt, "/cpus", "timebase-frequency", > > - SIFIVE_CLINT_TIMEBASE_FREQ); > > + timebase_frequency); > > qemu_fdt_setprop_cell(fdt, "/cpus", "#size-cells", 0x0); > > qemu_fdt_setprop_cell(fdt, "/cpus", "#address-cells", 0x1); > > qemu_fdt_add_subnode(fdt, "/cpus/cpu-map"); @@ -510,6 +510,7 > @@ > > static void virt_machine_init(MachineState *machine) > > target_ulong firmware_end_addr, kernel_start_addr; > > uint32_t fdt_load_addr; > > uint64_t kernel_entry; > > + uint64_t timebase_frequency = 0; > > DeviceState *mmio_plic, *virtio_plic, *pcie_plic; > > int i, j, base_hartid, hart_count; > > CPUState *cs; > > @@ -553,12 +554,20 @@ static void virt_machine_init(MachineState > *machine) > > hart_count, &error_abort); > > sysbus_realize(SYS_BUS_DEVICE(&s->soc[i]), &error_abort); > > > > + if (!timebase_frequency) { > > + timebase_frequency = RISCV_CPU(first_cpu)->env.frequency; > > + } > > + /* If vcpu's time frequency is not specified, we use default > frequency */ > > + if (!timebase_frequency) { > > + timebase_frequency = SIFIVE_CLINT_TIMEBASE_FREQ; > > + } > > + > > /* Per-socket CLINT */ > > sifive_clint_create( > > memmap[VIRT_CLINT].base + i * > memmap[VIRT_CLINT].size, > > memmap[VIRT_CLINT].size, base_hartid, hart_count, > > SIFIVE_SIP_BASE, SIFIVE_TIMECMP_BASE, > SIFIVE_TIME_BASE, > > - SIFIVE_CLINT_TIMEBASE_FREQ, true); > > + timebase_frequency, true); > > > > /* Per-socket PLIC hart topology configuration string */ > > plic_hart_config_len = > > @@ -610,7 +619,8 @@ static void virt_machine_init(MachineState > *machine) > > main_mem); > > > > /* create device tree */ > > - create_fdt(s, memmap, machine->ram_size, > machine->kernel_cmdline); > > + create_fdt(s, memmap, machine->ram_size, > machine->kernel_cmdline, > > + timebase_frequency); > > > > /* boot rom */ > > memory_region_init_rom(mask_rom, NULL, "riscv_virt_board.mrom", > > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c index > > 439dc89ee7..66f35bcbbf 100644 > > --- a/target/riscv/cpu.c > > +++ b/target/riscv/cpu.c > > @@ -494,6 +494,8 @@ static void riscv_cpu_realize(DeviceState *dev, > > Error **errp) > > > > riscv_cpu_register_gdb_regs_for_features(cs); > > > > + env->user_frequency = env->frequency; > > + > > qemu_init_vcpu(cs); > > cpu_reset(cs); > > > > @@ -531,6 +533,7 @@ static Property riscv_cpu_properties[] = { > > DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true), > > DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true), > > DEFINE_PROP_UINT64("resetvec", RISCVCPU, cfg.resetvec, > > DEFAULT_RSTVEC), > > + DEFINE_PROP_UINT64("time-frequency", RISCVCPU, env.frequency, 0), > > Why not set the default to SIFIVE_CLINT_TIMEBASE_FREQ? > When the time frequency is not specified, it will follow the host or the migration source. And we define 0 as equivalent to not specified time frequency. > Also, QEMU now has a clock API, is using that instead a better option? > Sorry, I didn't find the clock API. Could you tell me what the API is. I think that the time frequency is option of KVM VCPU. So it is appropriate to put this option in the CPU.

Yifei > Alistair > > > DEFINE_PROP_END_OF_LIST(), > > }; > > > > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h index > > 16d6050ead..f5b6c34176 100644 > > --- a/target/riscv/cpu.h > > +++ b/target/riscv/cpu.h > > @@ -243,6 +243,8 @@ struct CPURISCVState { > > uint64_t kvm_timer_time; > > uint64_t kvm_timer_compare; > > uint64_t kvm_timer_state; > > + uint64_t user_frequency; > > + uint64_t frequency; > > }; > > > > OBJECT_DECLARE_TYPE(RISCVCPU, RISCVCPUClass, > > -- > > 2.19.1 > > > >