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KVM: ARM: User space API for getting/setting co-proc registers
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The following three ioctls are implemented:
 -  KVM_GET_REG_LIST
 -  KVM_GET_ONE_REG
 -  KVM_SET_ONE_REG

Now we have a table for all the cp15 registers, we can drive a generic
API.

The register IDs carry the following encoding:

ARM registers are mapped using the lower 32 bits.  The upper 16 of that
is the register group type, or coprocessor number:

ARM 32-bit CP15 registers have the following id bit patterns:
  0x4002 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>

ARM 64-bit CP15 registers have the following id bit patterns:
  0x4003 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>

For futureproofing, we need to tell QEMU about the CP15 registers the
host lets the guest access.

It will need this information to restore a current guest on a future
CPU or perhaps a future KVM which allow some of these to be changed.

We use a separate table for these, as they're only for the userspace API.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
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Christoffer Dall committed Jan 23, 2013
1 parent 5b3e5e5 commit 1138245
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5 changes: 5 additions & 0 deletions Documentation/virtual/kvm/api.txt
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Expand Up @@ -1799,6 +1799,11 @@ is the register group type, or coprocessor number:
ARM core registers have the following id bit patterns:
0x4002 0000 0010 <index into the kvm_regs struct:16>

ARM 32-bit CP15 registers have the following id bit patterns:
0x4002 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>

ARM 64-bit CP15 registers have the following id bit patterns:
0x4003 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>


4.69 KVM_GET_ONE_REG
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9 changes: 9 additions & 0 deletions arch/arm/include/asm/kvm_coproc.h
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Expand Up @@ -34,5 +34,14 @@ int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_cp14_access(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run);

unsigned long kvm_arm_num_guest_msrs(struct kvm_vcpu *vcpu);
int kvm_arm_copy_msrindices(struct kvm_vcpu *vcpu, u64 __user *uindices);
void kvm_coproc_table_init(void);

struct kvm_one_reg;
int kvm_arm_copy_coproc_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
int kvm_arm_coproc_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *);
int kvm_arm_coproc_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *);
unsigned long kvm_arm_num_coproc_regs(struct kvm_vcpu *vcpu);
#endif /* __ARM_KVM_COPROC_H__ */
4 changes: 4 additions & 0 deletions arch/arm/include/asm/kvm_host.h
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Expand Up @@ -27,6 +27,7 @@
#define KVM_MEMORY_SLOTS 32
#define KVM_PRIVATE_MEM_SLOTS 4
#define KVM_COALESCED_MMIO_PAGE_OFFSET 1
#define KVM_HAVE_ONE_REG

#define KVM_VCPU_MAX_FEATURES 0

Expand Down Expand Up @@ -137,6 +138,9 @@ int kvm_unmap_hva_range(struct kvm *kvm,
unsigned long start, unsigned long end);
void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);

unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);

/* We do not have shadow page tables, hence the empty hooks */
static inline int kvm_age_hva(struct kvm *kvm, unsigned long hva)
{
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327 changes: 327 additions & 0 deletions arch/arm/kvm/coproc.c
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Expand Up @@ -18,6 +18,7 @@
*/
#include <linux/mm.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_host.h>
#include <asm/kvm_emulate.h>
Expand Down Expand Up @@ -347,13 +348,339 @@ int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run)
return emulate_cp15(vcpu, &params);
}

/******************************************************************************
* Userspace API
*****************************************************************************/

static bool index_to_params(u64 id, struct coproc_params *params)
{
switch (id & KVM_REG_SIZE_MASK) {
case KVM_REG_SIZE_U32:
/* Any unused index bits means it's not valid. */
if (id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK
| KVM_REG_ARM_COPROC_MASK
| KVM_REG_ARM_32_CRN_MASK
| KVM_REG_ARM_CRM_MASK
| KVM_REG_ARM_OPC1_MASK
| KVM_REG_ARM_32_OPC2_MASK))
return false;

params->is_64bit = false;
params->CRn = ((id & KVM_REG_ARM_32_CRN_MASK)
>> KVM_REG_ARM_32_CRN_SHIFT);
params->CRm = ((id & KVM_REG_ARM_CRM_MASK)
>> KVM_REG_ARM_CRM_SHIFT);
params->Op1 = ((id & KVM_REG_ARM_OPC1_MASK)
>> KVM_REG_ARM_OPC1_SHIFT);
params->Op2 = ((id & KVM_REG_ARM_32_OPC2_MASK)
>> KVM_REG_ARM_32_OPC2_SHIFT);
return true;
case KVM_REG_SIZE_U64:
/* Any unused index bits means it's not valid. */
if (id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK
| KVM_REG_ARM_COPROC_MASK
| KVM_REG_ARM_CRM_MASK
| KVM_REG_ARM_OPC1_MASK))
return false;
params->is_64bit = true;
params->CRm = ((id & KVM_REG_ARM_CRM_MASK)
>> KVM_REG_ARM_CRM_SHIFT);
params->Op1 = ((id & KVM_REG_ARM_OPC1_MASK)
>> KVM_REG_ARM_OPC1_SHIFT);
params->Op2 = 0;
params->CRn = 0;
return true;
default:
return false;
}
}

/* Decode an index value, and find the cp15 coproc_reg entry. */
static const struct coproc_reg *index_to_coproc_reg(struct kvm_vcpu *vcpu,
u64 id)
{
size_t num;
const struct coproc_reg *table, *r;
struct coproc_params params;

/* We only do cp15 for now. */
if ((id & KVM_REG_ARM_COPROC_MASK) >> KVM_REG_ARM_COPROC_SHIFT != 15)
return NULL;

if (!index_to_params(id, &params))
return NULL;

table = get_target_table(vcpu->arch.target, &num);
r = find_reg(&params, table, num);
if (!r)
r = find_reg(&params, cp15_regs, ARRAY_SIZE(cp15_regs));

/* Not saved in the cp15 array? */
if (r && !r->reg)
r = NULL;

return r;
}

/*
* These are the invariant cp15 registers: we let the guest see the host
* versions of these, so they're part of the guest state.
*
* A future CPU may provide a mechanism to present different values to
* the guest, or a future kvm may trap them.
*/
/* Unfortunately, there's no register-argument for mrc, so generate. */
#define FUNCTION_FOR32(crn, crm, op1, op2, name) \
static void get_##name(struct kvm_vcpu *v, \
const struct coproc_reg *r) \
{ \
u32 val; \
\
asm volatile("mrc p15, " __stringify(op1) \
", %0, c" __stringify(crn) \
", c" __stringify(crm) \
", " __stringify(op2) "\n" : "=r" (val)); \
((struct coproc_reg *)r)->val = val; \
}

FUNCTION_FOR32(0, 0, 0, 0, MIDR)
FUNCTION_FOR32(0, 0, 0, 1, CTR)
FUNCTION_FOR32(0, 0, 0, 2, TCMTR)
FUNCTION_FOR32(0, 0, 0, 3, TLBTR)
FUNCTION_FOR32(0, 0, 0, 6, REVIDR)
FUNCTION_FOR32(0, 1, 0, 0, ID_PFR0)
FUNCTION_FOR32(0, 1, 0, 1, ID_PFR1)
FUNCTION_FOR32(0, 1, 0, 2, ID_DFR0)
FUNCTION_FOR32(0, 1, 0, 3, ID_AFR0)
FUNCTION_FOR32(0, 1, 0, 4, ID_MMFR0)
FUNCTION_FOR32(0, 1, 0, 5, ID_MMFR1)
FUNCTION_FOR32(0, 1, 0, 6, ID_MMFR2)
FUNCTION_FOR32(0, 1, 0, 7, ID_MMFR3)
FUNCTION_FOR32(0, 2, 0, 0, ID_ISAR0)
FUNCTION_FOR32(0, 2, 0, 1, ID_ISAR1)
FUNCTION_FOR32(0, 2, 0, 2, ID_ISAR2)
FUNCTION_FOR32(0, 2, 0, 3, ID_ISAR3)
FUNCTION_FOR32(0, 2, 0, 4, ID_ISAR4)
FUNCTION_FOR32(0, 2, 0, 5, ID_ISAR5)
FUNCTION_FOR32(0, 0, 1, 1, CLIDR)
FUNCTION_FOR32(0, 0, 1, 7, AIDR)

/* ->val is filled in by kvm_invariant_coproc_table_init() */
static struct coproc_reg invariant_cp15[] = {
{ CRn( 0), CRm( 0), Op1( 0), Op2( 0), is32, NULL, get_MIDR },
{ CRn( 0), CRm( 0), Op1( 0), Op2( 1), is32, NULL, get_CTR },
{ CRn( 0), CRm( 0), Op1( 0), Op2( 2), is32, NULL, get_TCMTR },
{ CRn( 0), CRm( 0), Op1( 0), Op2( 3), is32, NULL, get_TLBTR },
{ CRn( 0), CRm( 0), Op1( 0), Op2( 6), is32, NULL, get_REVIDR },

{ CRn( 0), CRm( 1), Op1( 0), Op2( 0), is32, NULL, get_ID_PFR0 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 1), is32, NULL, get_ID_PFR1 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 2), is32, NULL, get_ID_DFR0 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 3), is32, NULL, get_ID_AFR0 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 4), is32, NULL, get_ID_MMFR0 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 5), is32, NULL, get_ID_MMFR1 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 6), is32, NULL, get_ID_MMFR2 },
{ CRn( 0), CRm( 1), Op1( 0), Op2( 7), is32, NULL, get_ID_MMFR3 },

{ CRn( 0), CRm( 2), Op1( 0), Op2( 0), is32, NULL, get_ID_ISAR0 },
{ CRn( 0), CRm( 2), Op1( 0), Op2( 1), is32, NULL, get_ID_ISAR1 },
{ CRn( 0), CRm( 2), Op1( 0), Op2( 2), is32, NULL, get_ID_ISAR2 },
{ CRn( 0), CRm( 2), Op1( 0), Op2( 3), is32, NULL, get_ID_ISAR3 },
{ CRn( 0), CRm( 2), Op1( 0), Op2( 4), is32, NULL, get_ID_ISAR4 },
{ CRn( 0), CRm( 2), Op1( 0), Op2( 5), is32, NULL, get_ID_ISAR5 },

{ CRn( 0), CRm( 0), Op1( 1), Op2( 1), is32, NULL, get_CLIDR },
{ CRn( 0), CRm( 0), Op1( 1), Op2( 7), is32, NULL, get_AIDR },
};

static int reg_from_user(void *val, const void __user *uaddr, u64 id)
{
/* This Just Works because we are little endian. */
if (copy_from_user(val, uaddr, KVM_REG_SIZE(id)) != 0)
return -EFAULT;
return 0;
}

static int reg_to_user(void __user *uaddr, const void *val, u64 id)
{
/* This Just Works because we are little endian. */
if (copy_to_user(uaddr, val, KVM_REG_SIZE(id)) != 0)
return -EFAULT;
return 0;
}

static int get_invariant_cp15(u64 id, void __user *uaddr)
{
struct coproc_params params;
const struct coproc_reg *r;

if (!index_to_params(id, &params))
return -ENOENT;

r = find_reg(&params, invariant_cp15, ARRAY_SIZE(invariant_cp15));
if (!r)
return -ENOENT;

return reg_to_user(uaddr, &r->val, id);
}

static int set_invariant_cp15(u64 id, void __user *uaddr)
{
struct coproc_params params;
const struct coproc_reg *r;
int err;
u64 val = 0; /* Make sure high bits are 0 for 32-bit regs */

if (!index_to_params(id, &params))
return -ENOENT;
r = find_reg(&params, invariant_cp15, ARRAY_SIZE(invariant_cp15));
if (!r)
return -ENOENT;

err = reg_from_user(&val, uaddr, id);
if (err)
return err;

/* This is what we mean by invariant: you can't change it. */
if (r->val != val)
return -EINVAL;

return 0;
}

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;

r = index_to_coproc_reg(vcpu, reg->id);
if (!r)
return get_invariant_cp15(reg->id, uaddr);

/* Note: copies two regs if size is 64 bit. */
return reg_to_user(uaddr, &vcpu->arch.cp15[r->reg], reg->id);
}

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;

r = index_to_coproc_reg(vcpu, reg->id);
if (!r)
return set_invariant_cp15(reg->id, uaddr);

/* Note: copies two regs if size is 64 bit */
return reg_from_user(&vcpu->arch.cp15[r->reg], uaddr, reg->id);
}

static u64 cp15_to_index(const struct coproc_reg *reg)
{
u64 val = KVM_REG_ARM | (15 << KVM_REG_ARM_COPROC_SHIFT);
if (reg->is_64) {
val |= KVM_REG_SIZE_U64;
val |= (reg->Op1 << KVM_REG_ARM_OPC1_SHIFT);
val |= (reg->CRm << KVM_REG_ARM_CRM_SHIFT);
} else {
val |= KVM_REG_SIZE_U32;
val |= (reg->Op1 << KVM_REG_ARM_OPC1_SHIFT);
val |= (reg->Op2 << KVM_REG_ARM_32_OPC2_SHIFT);
val |= (reg->CRm << KVM_REG_ARM_CRM_SHIFT);
val |= (reg->CRn << KVM_REG_ARM_32_CRN_SHIFT);
}
return val;
}

static bool copy_reg_to_user(const struct coproc_reg *reg, u64 __user **uind)
{
if (!*uind)
return true;

if (put_user(cp15_to_index(reg), *uind))
return false;

(*uind)++;
return true;
}

/* Assumed ordered tables, see kvm_coproc_table_init. */
static int walk_cp15(struct kvm_vcpu *vcpu, u64 __user *uind)
{
const struct coproc_reg *i1, *i2, *end1, *end2;
unsigned int total = 0;
size_t num;

/* We check for duplicates here, to allow arch-specific overrides. */
i1 = get_target_table(vcpu->arch.target, &num);
end1 = i1 + num;
i2 = cp15_regs;
end2 = cp15_regs + ARRAY_SIZE(cp15_regs);

BUG_ON(i1 == end1 || i2 == end2);

/* Walk carefully, as both tables may refer to the same register. */
while (i1 || i2) {
int cmp = cmp_reg(i1, i2);
/* target-specific overrides generic entry. */
if (cmp <= 0) {
/* Ignore registers we trap but don't save. */
if (i1->reg) {
if (!copy_reg_to_user(i1, &uind))
return -EFAULT;
total++;
}
} else {
/* Ignore registers we trap but don't save. */
if (i2->reg) {
if (!copy_reg_to_user(i2, &uind))
return -EFAULT;
total++;
}
}

if (cmp <= 0 && ++i1 == end1)
i1 = NULL;
if (cmp >= 0 && ++i2 == end2)
i2 = NULL;
}
return total;
}

unsigned long kvm_arm_num_coproc_regs(struct kvm_vcpu *vcpu)
{
return ARRAY_SIZE(invariant_cp15)
+ walk_cp15(vcpu, (u64 __user *)NULL);
}

int kvm_arm_copy_coproc_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
{
unsigned int i;
int err;

/* Then give them all the invariant registers' indices. */
for (i = 0; i < ARRAY_SIZE(invariant_cp15); i++) {
if (put_user(cp15_to_index(&invariant_cp15[i]), uindices))
return -EFAULT;
uindices++;
}

err = walk_cp15(vcpu, uindices);
if (err > 0)
err = 0;
return err;
}

void kvm_coproc_table_init(void)
{
unsigned int i;

/* Make sure tables are unique and in order. */
for (i = 1; i < ARRAY_SIZE(cp15_regs); i++)
BUG_ON(cmp_reg(&cp15_regs[i-1], &cp15_regs[i]) >= 0);

/* 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]);
}

/**
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