On Mon, Sep 17, 2012 at 3:28 AM, Rusty Russell <rusty.russell@xxxxxxxxxx> wrote:
> Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx> writes:
>
>> Is this the 3/3 patch or is something missing?
>
> Ah yes, the [PATCH 3/3] was missing. That will teach me to cut & paste
> the subject line from the patch.
>
>>> +ARM CCSIDR registers are demultiplexed by CSSELR value:
>>> + 0x4003 0000 0011 <CSSELR>
>>
>> then this is wrong right?
>>
>> shouldn't it be:
>>
>> + 0x4003 0000 0011 <dmux id:8> <selector:8>
>>
>> or
>>
>> + 0x4003 0000 0011 00 <CSSELR:8>
>>
>> ???
>
> Good point, I changed the implementation later. It's not wrong, but
> it's pretty misleading. Fixed below.
>
>>> +static bool is_valid_cache(u32 val)
>>> +{
>>> + u32 ctype;
>>> +
>>> + if (val >= CSSELR_MAX)
>>> + return -ENOENT;
>>> +
>>> + /* Bottom bit is Instruction or Data bit. Next 3 bits are level. */
>>> + ctype = cache_levels & (7 << ((val>>1));
>>
>> this looks wrong, shouldn't this be
>>
>> + level = (val >> 1) & 7;
>> + ctype = (cache_levels >> (level * 3)) & 7;
>>
>> ???
>
> Good catch. Because we check val < CSSELR_MAX here, we can simplify the
> level calc though:
>
> level = (val >> 1);
> ctype = (cache_levels >> (level * 3)) & 7;
>
> (This happens to make no difference on the fastmodel, since it only has
> level 0 and 1 caches anyway):
>
> Before:
>
> Cache 0 (icache): r/o read-alloc 256 sets of 2 assoc 16 linesize
> Cache 0: write-back read-alloc write-alloc 256 sets of 2 assoc 16 linesize
> Cache 1: write-back read-alloc write-alloc 512 sets of 16 assoc 16 linesize
>
> After:
>
> Cache 0 (icache): r/o read-alloc 256 sets of 2 assoc 16 linesize
> Cache 0: write-back read-alloc write-alloc 256 sets of 2 assoc 16 linesize
> Cache 1: write-back read-alloc write-alloc 512 sets of 16 assoc 16 linesize
>
> ---
> Subject: KVM: ARM: Demux CCSIDR in the userspace API.
>
> The Cache Size Selection Register (CSSELR) selects the current Cache
> Size ID Register (CCSIDR). You write which cache you are interested
> in to CSSELR, and read the information out of CCSIDR.
>
> Which cache numbers are valid is known by reading the Cache Level ID
> Register (CLIDR).
>
> To export this state to userspace, we add a KVM_REG_ARM_DEMUX
> numberspace (17), which uses 8 bits to represent which register is
> being demultiplexed (0 for CCSIDR), and the lower 8 bits to represent
> this demultiplexing (in our case, the CSSELR value, which is 4 bits).
>
> Signed-off-by: Rusty Russell <rusty.russell@xxxxxxxxxx>
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index dbde8ae..2d2f6ff 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1757,6 +1757,8 @@ ARM 32-bit CP15 registers have the following id bit patterns:
> ARM 64-bit CP15 registers have the following id bit patterns:
> 0x4003 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>
>
> +ARM CCSIDR registers are demultiplexed by CSSELR value:
> + 0x4003 0000 0011 00 <csselr:8>
>
> 4.69 KVM_GET_ONE_REG
>
> diff --git a/arch/arm/include/asm/kvm.h b/arch/arm/include/asm/kvm.h
> index 9f36b24..2034ea2 100644
> --- a/arch/arm/include/asm/kvm.h
> +++ b/arch/arm/include/asm/kvm.h
> @@ -94,4 +94,12 @@ struct kvm_reg_list {
> #define KVM_REG_ARM_CORE (0x0010 << KVM_REG_ARM_COPROC_SHIFT)
> #define KVM_REG_ARM_CORE_REG(name) (offsetof(struct kvm_regs, name) / 4)
>
> +/* Some registers need more space to represent values. */
> +#define KVM_REG_ARM_DEMUX (0x0011 << KVM_REG_ARM_COPROC_SHIFT)
> +#define KVM_REG_ARM_DEMUX_ID_MASK 0x000000000000FF00
> +#define KVM_REG_ARM_DEMUX_ID_SHIFT 8
> +#define KVM_REG_ARM_DEMUX_ID_CCSIDR (0x00 << KVM_REG_ARM_DEMUX_ID_SHIFT)
> +#define KVM_REG_ARM_DEMUX_VAL_MASK 0x00000000000000FF
> +#define KVM_REG_ARM_DEMUX_VAL_SHIFT 0
> +
> #endif /* __ARM_KVM_H__ */
> diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
> index 5c7f5fd..0200820 100644
> --- a/arch/arm/kvm/coproc.c
> +++ b/arch/arm/kvm/coproc.c
> @@ -67,6 +67,12 @@ struct coproc_reg {
> u64 val;
> };
>
> +/* 3 bits per cache level, as per CLIDR, but non-existent caches always 0 */
> +static u32 cache_levels;
> +
> +/* CSSELR values; used to index KVM_REG_ARM_DEMUX_ID_CCSIDR */
> +#define CSSELR_MAX 12
> +
> static void print_cp_instr(const struct coproc_params *p)
> {
> /* Look, we even formatted it for you to paste into the table! */
> @@ -765,11 +771,112 @@ static int set_invariant_cp15(u64 id, void __user *uaddr)
> return 0;
> }
>
> +static bool is_valid_cache(u32 val)
> +{
> + u32 level, ctype;
> +
> + if (val >= CSSELR_MAX)
> + return -ENOENT;
> +
> + /* Bottom bit is Instruction or Data bit. Next 3 bits are level. */
> + level = (val >> 1);
> + ctype = (cache_levels >> (level * 3)) & 7;
> +
> + switch (ctype) {
> + case 0: /* No cache */
> + return false;
> + case 1: /* Instruction cache only */
> + return (val & 1);
> + case 2: /* Data cache only */
> + case 4: /* Unified cache */
> + return !(val & 1);
> + case 3: /* Separate instruction and data caches */
> + return true;
> + default: /* Reserved: we can't know instruction or data. */
> + return false;
> + }
> +}
> +
> +/* Which cache CCSIDR represents depends on CSSELR value. */
> +static u32 get_ccsidr(u32 csselr)
> +{
> + u32 ccsidr;
> +
> + /* Make sure noone else changes CSSELR during this! */
> + local_irq_disable();
> + /* Put value into CSSELR */
> + asm volatile("mcr p15, 2, %0, c0, c0, 0" : : "r" (csselr));
> + /* Read result out of CCSIDR */
> + asm volatile("mrc p15, 1, %0, c0, c0, 0" : "=r" (ccsidr));
> + local_irq_enable();
> +
> + return ccsidr;
> +}
> +
> +static int demux_c15_get(u64 id, void __user *uaddr)
> +{
> + u32 val;
> + u32 __user *uval = uaddr;
> +
> + /* Fail if we have unknown bits set. */
> + if (id & ~(KVM_REG_ARCH_MASK|KVM_REG_SIZE_MASK|KVM_REG_ARM_COPROC_MASK
> + | ((1 << KVM_REG_ARM_COPROC_SHIFT)-1)))
> + return -ENOENT;
> +
> + switch (id & KVM_REG_ARM_DEMUX_ID_MASK) {
> + case KVM_REG_ARM_DEMUX_ID_CCSIDR:
> + if (KVM_REG_SIZE(id) != 4)
> + return -ENOENT;
> + val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
> + >> KVM_REG_ARM_DEMUX_VAL_SHIFT;
> + if (!is_valid_cache(val))
> + return -ENOENT;
> +
> + return put_user(get_ccsidr(val), uval);
> + default:
> + return -ENOENT;
> + }
> +}
> +
> +static int demux_c15_set(u64 id, void __user *uaddr)
> +{
> + u32 val, newval;
> + u32 __user *uval = uaddr;
> +
> + /* Fail if we have unknown bits set. */
> + if (id & ~(KVM_REG_ARCH_MASK|KVM_REG_SIZE_MASK|KVM_REG_ARM_COPROC_MASK
> + | ((1 << KVM_REG_ARM_COPROC_SHIFT)-1)))
> + return -ENOENT;
> +
> + switch (id & KVM_REG_ARM_DEMUX_ID_MASK) {
> + case KVM_REG_ARM_DEMUX_ID_CCSIDR:
> + if (KVM_REG_SIZE(id) != 4)
> + return -ENOENT;
> + val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
> + >> KVM_REG_ARM_DEMUX_VAL_SHIFT;
> + if (!is_valid_cache(val))
> + return -ENOENT;
> +
> + if (get_user(newval, uval))
> + return -EFAULT;
> +
> + /* This is also invariant: you can't change it. */
> + if (newval != get_ccsidr(val))
> + return -EINVAL;
> + return 0;
> + default:
> + return -ENOENT;
> + }
> +}
> +
> int kvm_arm_coproc_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> {
> const struct coproc_reg *r;
> void __user *uaddr = (void __user *)(long)reg->addr;
>
> + if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_DEMUX)
> + return demux_c15_get(reg->id, uaddr);
> +
> r = index_to_coproc_reg(vcpu, reg->id);
> if (!r)
> return get_invariant_cp15(reg->id, uaddr);
> @@ -783,6 +890,9 @@ int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> const struct coproc_reg *r;
> void __user *uaddr = (void __user *)(long)reg->addr;
>
> + if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_DEMUX)
> + return demux_c15_set(reg->id, uaddr);
> +
> r = index_to_coproc_reg(vcpu, reg->id);
> if (!r)
> return set_invariant_cp15(reg->id, uaddr);
> @@ -791,6 +901,33 @@ int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> return reg_from_user(&vcpu->arch.cp15[r->reg], uaddr, reg->id);
> }
>
> +static unsigned int num_demux_regs(void)
> +{
> + unsigned int i, count = 0;
> +
> + for (i = 0; i < CSSELR_MAX; i++)
> + if (is_valid_cache(i))
> + count++;
> +
> + return count;
> +}
> +
> +static int write_demux_regids(u64 __user *uindices)
> +{
> + u64 val = KVM_REG_ARM | KVM_REG_SIZE_U32 | KVM_REG_ARM_DEMUX;
> + unsigned int i;
> +
> + val |= KVM_REG_ARM_DEMUX_ID_CCSIDR;
> + for (i = 0; i < CSSELR_MAX; i++) {
> + if (!is_valid_cache(i))
> + continue;
> + if (put_user(val | i, uindices))
> + return -EFAULT;
> + uindices++;
> + }
> + return 0;
> +}
> +
> static int cmp_reg(const struct coproc_reg *i1, const struct coproc_reg *i2)
> {
> BUG_ON(i1 == i2);
> @@ -882,6 +1019,7 @@ static int walk_cp15(struct kvm_vcpu *vcpu, u64 __user *uind)
> unsigned long kvm_arm_num_coproc_regs(struct kvm_vcpu *vcpu)
> {
> return ARRAY_SIZE(invariant_cp15)
> + + num_demux_regs()
> + walk_cp15(vcpu, (u64 __user *)NULL);
> }
>
> @@ -898,9 +1036,11 @@ int kvm_arm_copy_coproc_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
> }
>
> err = walk_cp15(vcpu, uindices);
> - if (err > 0)
> - err = 0;
> - return err;
> + if (err < 0)
> + return err;
> + uindices += err;
> +
> + return write_demux_regids(uindices);
> }
>
> void kvm_coproc_table_init(void)
> @@ -917,6 +1057,23 @@ void kvm_coproc_table_init(void)
> /* We abuse the reset function to overwrite the table itself. */
> for (i = 0; i < ARRAY_SIZE(invariant_cp15); i++)
> invariant_cp15[i].reset(NULL, &invariant_cp15[i]);
> +
> + /*
> + * CLIDR format is awkward, so clean it up. See ARM B4.1.20:
> + *
> + * If software reads the Cache Type fields from Ctype1
> + * upwards, once it has seen a value of 0b000, no caches
> + * exist at further-out levels of the hierarchy. So, for
> + * example, if Ctype3 is the first Cache Type field with a
> + * value of 0b000, the values of Ctype4 to Ctype7 must be
> + * ignored.
> + */
> + asm volatile("mrc p15, 1, %0, c0, c0, 1" : "=r" (cache_levels));
> + for (i = 0; i < 7; i++)
> + if (((cache_levels >> (i*3)) & 7) == 0)
> + break;
> + /* Clear all higher bits. */
> + cache_levels &= (1 << (i*3))-1;
> }
>
> /**
thanks,
applied.
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