Re: [Qemu-devel] [PATCH 5/5] hw: arm_gic_kvm: Add KVM VGIC save/restore logic

[Paolo Bonzini]

Il 25/08/2013 17:47, Alexander Graf ha scritto:
> 
> On 23.08.2013, at 21:10, Christoffer Dall wrote:
> 
>> Save and restore the ARM KVM VGIC state from the kernel.  We rely on
>> QEMU to marshal the GICState data structure and therefore simply
>> synchronize the kernel state with the QEMU emulated state in both
>> directions.
>>
>> We take some care on the restore path to check the VGIC has been
>> configured with enough IRQs and CPU interfaces that we can properly
>> restore the state, and for separate set/clear registers we first fully
>> clear the registers and then set the required bits.
>>
>> Signed-off-by: Christoffer Dall <address@hidden>
>> ---
>> hw/intc/arm_gic_common.c    |    2 +
>> hw/intc/arm_gic_kvm.c       |  418 
>> ++++++++++++++++++++++++++++++++++++++++++-
>> hw/intc/gic_internal.h      |    1 +
>> include/migration/vmstate.h |    6 +
>> 4 files changed, 425 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/intc/arm_gic_common.c b/hw/intc/arm_gic_common.c
>> index a50ded2..f39bdc1 100644
>> --- a/hw/intc/arm_gic_common.c
>> +++ b/hw/intc/arm_gic_common.c
>> @@ -77,6 +77,8 @@ static const VMStateDescription vmstate_gic = {
>>         VMSTATE_UINT16_ARRAY(running_priority, GICState, NCPU),
>>         VMSTATE_UINT16_ARRAY(current_pending, GICState, NCPU),
>>         VMSTATE_UINT8_2DARRAY(binary_point, GICState, 2, NCPU),
>> +        VMSTATE_UINT32_2DARRAY(active_prio, GICState, 4, NCPU),
>> +        VMSTATE_UINT32(num_irq, GICState),
>>         VMSTATE_END_OF_LIST()
>>     }
>> };
>> diff --git a/hw/intc/arm_gic_kvm.c b/hw/intc/arm_gic_kvm.c
>> index 9f0a852..9785281 100644
>> --- a/hw/intc/arm_gic_kvm.c
>> +++ b/hw/intc/arm_gic_kvm.c
>> @@ -23,6 +23,15 @@
>> #include "kvm_arm.h"
>> #include "gic_internal.h"
>>
>> +//#define DEBUG_GIC_KVM
>> +
>> +#ifdef DEBUG_GIC_KVM
>> +#define DPRINTF(fmt, ...) \
>> +do { fprintf(stderr, "arm_gic: " fmt , ## __VA_ARGS__); } while (0)
>> +#else
>> +#define DPRINTF(fmt, ...) do {} while(0)
> 
> You really want to make DPRINTF still be format checked by the compiler. 
> Check out hw/intc/openpic.c for an example how to get there.
> 
>> +#endif
>> +
>> #define TYPE_KVM_ARM_GIC "kvm-arm-gic"
>> #define KVM_ARM_GIC(obj) \
>>      OBJECT_CHECK(GICState, (obj), TYPE_KVM_ARM_GIC)
>> @@ -73,14 +82,419 @@ static void kvm_arm_gic_set_irq(void *opaque, int irq, 
>> int level)
>>     kvm_set_irq(kvm_state, kvm_irq, !!level);
>> }
>>
>> +static bool kvm_arm_gic_can_save_restore(GICState *s)
>> +{
>> +    KVMARMGICClass *kgc = KVM_ARM_GIC_GET_CLASS(s);
>> +    return kgc->dev_fd >= 0;
>> +}
>> +
>> +static void kvm_arm_gic_reg_access(GICState *s, int group, int offset,
>> +                                   int cpu, uint32_t *val, bool write)
>> +{
>> +    KVMARMGICClass *kgc = KVM_ARM_GIC_GET_CLASS(s);
>> +    struct kvm_device_attr attr;
>> +    int type;
>> +
>> +    cpu = cpu & 0xff;
>> +
>> +    attr.flags = 0;
>> +    attr.group = group;
>> +    attr.attr = (((uint64_t)cpu << KVM_DEV_ARM_VGIC_CPUID_SHIFT) &
>> +                 KVM_DEV_ARM_VGIC_CPUID_MASK) |
>> +                (((uint64_t)offset << KVM_DEV_ARM_VGIC_OFFSET_SHIFT) &
>> +                 KVM_DEV_ARM_VGIC_OFFSET_MASK);
>> +    attr.addr = (uint64_t)(long)val;
> 
> uintptr_t?
> 
>> +
>> +    if (write) {
>> +        type = KVM_SET_DEVICE_ATTR;
>> +    } else {
>> +        type = KVM_GET_DEVICE_ATTR;
>> +    }
>> +
>> +    if (kvm_device_ioctl(kgc->dev_fd, type, &attr) < 0) {
>> +            fprintf(stderr, "KVM_{SET/GET}_DEVICE_ATTR failed: %s\n",
>> +                    strerror(errno));
>> +            abort();
>> +    }
>> +}
>> +
>> +static void kvm_arm_gic_dist_reg_access(GICState *s, int offset, int cpu,
>> +                                        uint32_t *val, bool write)
>> +{
>> +    kvm_arm_gic_reg_access(s, KVM_DEV_ARM_VGIC_GRP_DIST_REGS,
>> +                           offset, cpu, val, write);
>> +}
>> +
>> +static void kvm_arm_gic_cpu_reg_access(GICState *s, int offset, int cpu,
>> +                                       uint32_t *val, bool write)
>> +{
>> +    kvm_arm_gic_reg_access(s, KVM_DEV_ARM_VGIC_GRP_CPU_REGS,
>> +                           offset, cpu, val, write);
>> +}
>> +
>> +#define for_each_irq_reg(_ctr, _max_irq, _field_width) \
>> +    for (_ctr = 0; _ctr < ((_max_irq) / (32 / (_field_width))); _ctr++)
>> +
>> +/*
>> + * Translate from the in-kernel field for an IRQ value to/from the qemu
>> + * representation.
>> + */
>> +typedef void (*vgic_translate_fn)(GICState *s, int irq, int cpu,
>> +                                  uint32_t *field, bool to_kernel);
>> +
>> +/* synthetic translate function used for clear/set registers to completely
>> + * clear a setting using a clear-register before setting the remaing bits
>> + * using a set-register */
>> +static void translate_clear(GICState *s, int irq, int cpu,
>> +                            uint32_t *field, bool to_kernel)
>> +{
>> +    if (to_kernel) {
>> +        *field = ~0;
>> +    } else {
>> +        /* does not make sense: qemu model doesn't use set/clear regs */
>> +        abort();
>> +    }
> 
> I don't understand the to_kernel bits. I thought we're in a device file that 
> only works with KVM?

The opposite of "to_kernel" is "from_kernel".

IIUC this is for GIC registers that are modelled as a pair of MMIO
registers, one with write-1-sets and one with write-1-clears semantics.
 The patch is first writing all ones to the w1c register, and then
writing the actual value to the w1s register.

The way we solved this for x86 is that the set-registers, when called
from userspace, also clear the zero bits.  See the "host_initiated"
parts in arch/x86/kvm/x86.c.  However, this would be an ABI change for
ARM, so Christoffer's solution is also fine.

One comment on the function names:

kvm_arm_gic_dist_readr
kvm_arm_gic_dist_writer

Why not get_reg/set_reg (I was quite surprised to see readr instead of
reader :) and it took me a while to understand the convention)?  Or if
the name is too long, s/readr/get/ and s/writer/set/ would be enough to
match the ioctls.

Paolo

>> +}
>> +
>> +static void translate_enabled(GICState *s, int irq, int cpu,
>> +                              uint32_t *field, bool to_kernel)
>> +{
>> +    int cm = (irq < GIC_INTERNAL) ? (1 << cpu) : ALL_CPU_MASK;
>> +
>> +    if (to_kernel) {
>> +        *field = GIC_TEST_ENABLED(irq, cm);
>> +    } else {
>> +        if (*field & 1) {
>> +            GIC_SET_ENABLED(irq, cm);
>> +        }
>> +    }
>> +}
>> +
>> +static void translate_pending(GICState *s, int irq, int cpu,
>> +                              uint32_t *field, bool to_kernel)
>> +{
>> +    int cm = (irq < GIC_INTERNAL) ? (1 << cpu) : ALL_CPU_MASK;
>> +
>> +    if (to_kernel) {
>> +        *field = GIC_TEST_PENDING(irq, cm);
>> +    } else {
>> +        if (*field & 1) {
>> +            GIC_SET_PENDING(irq, cm);
>> +            /* TODO: Capture is level-line is held high in the kernel */
>> +        }
>> +    }
>> +}
>> +
>> +static void translate_active(GICState *s, int irq, int cpu,
>> +                             uint32_t *field, bool to_kernel)
>> +{
>> +    int cm = (irq < GIC_INTERNAL) ? (1 << cpu) : ALL_CPU_MASK;
>> +
>> +    if (to_kernel) {
>> +        *field = GIC_TEST_ACTIVE(irq, cm);
>> +    } else {
>> +        if (*field & 1) {
>> +            GIC_SET_ACTIVE(irq, cm);
>> +        }
>> +    }
>> +}
>> +
>> +static void translate_trigger(GICState *s, int irq, int cpu,
>> +                            uint32_t *field, bool to_kernel)
>> +{
>> +    if (to_kernel) {
>> +        *field = (GIC_TEST_TRIGGER(irq)) ? 0x2 : 0x0;
>> +    } else {
>> +        if (*field & 0x2) {
>> +            GIC_SET_TRIGGER(irq);
>> +        }
>> +    }
>> +}
>> +
>> +static void translate_priority(GICState *s, int irq, int cpu,
>> +                               uint32_t *field, bool to_kernel)
>> +{
>> +    if (to_kernel) {
>> +        *field = GIC_GET_PRIORITY(irq, cpu) & 0xff;
>> +    } else {
>> +        GIC_SET_PRIORITY(irq, cpu, *field & 0xff);
>> +    }
>> +}
>> +
>> +static void translate_targets(GICState *s, int irq, int cpu,
>> +                              uint32_t *field, bool to_kernel)
>> +{
>> +    if (to_kernel) {
>> +        *field = s->irq_target[irq] & 0xff;
>> +    } else {
>> +        s->irq_target[irq] = *field & 0xff;
>> +    }
>> +}
>> +
>> +static void translate_sgisource(GICState *s, int irq, int cpu,
>> +                                uint32_t *field, bool to_kernel)
>> +{
>> +    if (to_kernel) {
>> +        *field = s->sgi_source[irq][cpu] & 0xff;
>> +    } else {
>> +        s->sgi_source[irq][cpu] = *field & 0xff;
>> +    }
>> +}
>> +
>> +/* Read a register group from the kernel VGIC */
>> +static void kvm_arm_gic_dist_readr(GICState *s, uint32_t offset, int width,
>> +                                   int maxirq, vgic_translate_fn 
>> translate_fn)
>> +{
>> +    uint32_t reg;
>> +    int i;
>> +    int j;
>> +    int irq;
>> +    int cpu;
>> +    int regsz = 32 / width; /* irqs per kernel register */
>> +    uint32_t field;
>> +
>> +    for_each_irq_reg(i, maxirq, width) {
>> +        irq = i * regsz;
>> +        cpu = 0;
>> +        while ((cpu < s->num_cpu && irq < GIC_INTERNAL) || cpu == 0) {
>> +            kvm_arm_gic_dist_reg_access(s, offset, cpu, &reg, false);
>> +            for (j = 0; j < regsz; j++) {
>> +                field = reg >> (j * width) & ((1 << width) - 1);
>> +                translate_fn(s, irq + j, cpu, &field, false);
>> +            }
>> +
>> +            cpu++;
>> +        }
>> +        offset += 4;
>> +    }
>> +}
>> +
>> +/* Write a register group to the kernel VGIC */
>> +static void kvm_arm_gic_dist_writer(GICState *s, uint32_t offset, int width,
>> +                                    int maxirq, vgic_translate_fn 
>> translate_fn)
>> +{
>> +    uint32_t reg;
>> +    int i;
>> +    int j;
>> +    int irq;
>> +    int cpu;
>> +    int regsz = 32 / width; /* irqs per kernel register */
>> +    uint32_t field;
>> +
>> +    for_each_irq_reg(i, maxirq, width) {
>> +        irq = i * regsz;
>> +        cpu = 0;
>> +        while ((cpu < s->num_cpu && irq < GIC_INTERNAL) || cpu == 0) {
>> +            reg = 0;
>> +            for (j = 0; j < regsz; j++) {
>> +                translate_fn(s, irq + j, cpu, &field, true);
>> +                reg |= (field & ((1 << width) - 1)) << (j * width);
>> +            }
>> +            kvm_arm_gic_dist_reg_access(s, offset, cpu, &reg, true);
>> +
>> +            cpu++;
>> +        }
>> +        offset += 4;
>> +    }
>> +}
>> +
>> static void kvm_arm_gic_put(GICState *s)
>> {
>> -    /* TODO: there isn't currently a kernel interface to set the GIC state 
>> */
>> +    uint32_t reg;
>> +    int i;
>> +    int cpu;
>> +    int num_cpu;
>> +    int num_irq;
>> +
>> +    if (!kvm_arm_gic_can_save_restore(s)) {
>> +            DPRINTF("Cannot put kernel gic state, no kernel interface");
>> +            return;
>> +    }
>> +
>> +    /* Note: We do the restore in a slightly different order than the save
>> +     * (where the order doesn't matter and is simply ordered according to 
>> the
>> +     * register offset values */
>> +
>> +    /*****************************************************************
>> +     * Distributor State
>> +     */
>> +
>> +    /* s->enabled -> GICD_CTLR */
>> +    reg = s->enabled;
>> +    kvm_arm_gic_dist_reg_access(s, 0x0, 0, &reg, true);
>> +
>> +    /* Sanity checking on GICD_TYPER and s->num_irq, s->num_cpu */
>> +    kvm_arm_gic_dist_reg_access(s, 0x4, 0, &reg, false);
>> +    num_irq = ((reg & 0x1f) + 1) * 32;
>> +    num_cpu = ((reg & 0xe0) >> 5) + 1;
>> +
>> +    if (num_irq < s->num_irq) {
>> +            fprintf(stderr, "Restoring %u IRQs, but kernel supports max 
>> %d\n",
>> +                    s->num_irq, num_irq);
>> +            abort();
>> +    } else if (num_cpu != s->num_cpu ) {
>> +            fprintf(stderr, "Restoring %u CPU interfaces, kernel only has 
>> %d\n",
>> +                    s->num_cpu, num_cpu);
>> +            /* Did we not create the VCPUs in the kernel yet? */
>> +            abort();
>> +    }
>> +
>> +    /* TODO: Consider checking compatibility with the IIDR ? */
>> +
>> +    /* irq_state[n].enabled -> GICD_ISENABLERn */
>> +    kvm_arm_gic_dist_writer(s, 0x180, 1, s->num_irq, translate_clear);
>> +    kvm_arm_gic_dist_writer(s, 0x100, 1, s->num_irq, translate_enabled);
> 
> Don't these magic numbers have #define'd equivalents in their GIC 
> implementation header file? Then you don't need the comments above each of 
> these.
> 
> I also find the function names quite long, but I guess as long as everything 
> still fits that doesn't really matter.
> 
> 
> Alex
> 
> 
>