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KVM: arm/arm64: Unify 32bit fault injection
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Both arm and arm64 implementations are capable of injecting
faults, and yet have completely divergent implementations,
leading to different bugs and reduced maintainability.

Let's elect the arm64 version as the canonical one
and move it into aarch32.c, which is common to both
architectures.

Reviewed-by: Christoffer Dall <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Signed-off-by: Christoffer Dall <[email protected]>
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@chazy
Marc Zyngier authored and chazy committed Nov 6, 2017
1 parent 3eb4271 commit 74a64a9
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Showing 5 changed files with 131 additions and 218 deletions.
36 changes: 33 additions & 3 deletions arch/arm/include/asm/kvm_emulate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,22 @@
#include <asm/kvm_arm.h>
#include <asm/cputype.h>

/* arm64 compatibility macros */
#define COMPAT_PSR_MODE_ABT ABT_MODE
#define COMPAT_PSR_MODE_UND UND_MODE
#define COMPAT_PSR_T_BIT PSR_T_BIT
#define COMPAT_PSR_I_BIT PSR_I_BIT
#define COMPAT_PSR_A_BIT PSR_A_BIT
#define COMPAT_PSR_E_BIT PSR_E_BIT
#define COMPAT_PSR_IT_MASK PSR_IT_MASK

unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num);

static inline unsigned long *vcpu_reg32(struct kvm_vcpu *vcpu, u8 reg_num)
{
return vcpu_reg(vcpu, reg_num);
}

unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu);

static inline unsigned long vcpu_get_reg(struct kvm_vcpu *vcpu,
Expand All @@ -42,10 +57,25 @@ static inline void vcpu_set_reg(struct kvm_vcpu *vcpu, u8 reg_num,

bool kvm_condition_valid32(const struct kvm_vcpu *vcpu);
void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr);
void kvm_inject_undefined(struct kvm_vcpu *vcpu);
void kvm_inject_undef32(struct kvm_vcpu *vcpu);
void kvm_inject_dabt32(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt32(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_vabt(struct kvm_vcpu *vcpu);
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);

static inline void kvm_inject_undefined(struct kvm_vcpu *vcpu)
{
kvm_inject_undef32(vcpu);
}

static inline void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
kvm_inject_dabt32(vcpu, addr);
}

static inline void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
kvm_inject_pabt32(vcpu, addr);
}

static inline bool kvm_condition_valid(const struct kvm_vcpu *vcpu)
{
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139 changes: 0 additions & 139 deletions arch/arm/kvm/emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -165,145 +165,6 @@ unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu)
* Inject exceptions into the guest
*/

static u32 exc_vector_base(struct kvm_vcpu *vcpu)
{
u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);
u32 vbar = vcpu_cp15(vcpu, c12_VBAR);

if (sctlr & SCTLR_V)
return 0xffff0000;
else /* always have security exceptions */
return vbar;
}

/*
* Switch to an exception mode, updating both CPSR and SPSR. Follow
* the logic described in AArch32.EnterMode() from the ARMv8 ARM.
*/
static void kvm_update_psr(struct kvm_vcpu *vcpu, unsigned long mode)
{
unsigned long cpsr = *vcpu_cpsr(vcpu);
u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);

*vcpu_cpsr(vcpu) = (cpsr & ~MODE_MASK) | mode;

switch (mode) {
case FIQ_MODE:
*vcpu_cpsr(vcpu) |= PSR_F_BIT;
/* Fall through */
case ABT_MODE:
case IRQ_MODE:
*vcpu_cpsr(vcpu) |= PSR_A_BIT;
/* Fall through */
default:
*vcpu_cpsr(vcpu) |= PSR_I_BIT;
}

*vcpu_cpsr(vcpu) &= ~(PSR_IT_MASK | PSR_J_BIT | PSR_E_BIT | PSR_T_BIT);

if (sctlr & SCTLR_TE)
*vcpu_cpsr(vcpu) |= PSR_T_BIT;
if (sctlr & SCTLR_EE)
*vcpu_cpsr(vcpu) |= PSR_E_BIT;

/* Note: These now point to the mode banked copies */
*vcpu_spsr(vcpu) = cpsr;
}

/**
* kvm_inject_undefined - inject an undefined exception into the guest
* @vcpu: The VCPU to receive the undefined exception
*
* It is assumed that this code is called from the VCPU thread and that the
* VCPU therefore is not currently executing guest code.
*
* Modelled after TakeUndefInstrException() pseudocode.
*/
void kvm_inject_undefined(struct kvm_vcpu *vcpu)
{
unsigned long cpsr = *vcpu_cpsr(vcpu);
bool is_thumb = (cpsr & PSR_T_BIT);
u32 vect_offset = 4;
u32 return_offset = (is_thumb) ? 2 : 4;

kvm_update_psr(vcpu, UND_MODE);
*vcpu_reg(vcpu, 14) = *vcpu_pc(vcpu) - return_offset;

/* Branch to exception vector */
*vcpu_pc(vcpu) = exc_vector_base(vcpu) + vect_offset;
}

/*
* Modelled after TakeDataAbortException() and TakePrefetchAbortException
* pseudocode.
*/
static void inject_abt(struct kvm_vcpu *vcpu, bool is_pabt, unsigned long addr)
{
unsigned long cpsr = *vcpu_cpsr(vcpu);
bool is_thumb = (cpsr & PSR_T_BIT);
u32 vect_offset;
u32 return_offset = (is_thumb) ? 4 : 0;
bool is_lpae;

kvm_update_psr(vcpu, ABT_MODE);
*vcpu_reg(vcpu, 14) = *vcpu_pc(vcpu) + return_offset;

if (is_pabt)
vect_offset = 12;
else
vect_offset = 16;

/* Branch to exception vector */
*vcpu_pc(vcpu) = exc_vector_base(vcpu) + vect_offset;

if (is_pabt) {
/* Set IFAR and IFSR */
vcpu_cp15(vcpu, c6_IFAR) = addr;
is_lpae = (vcpu_cp15(vcpu, c2_TTBCR) >> 31);
/* Always give debug fault for now - should give guest a clue */
if (is_lpae)
vcpu_cp15(vcpu, c5_IFSR) = 1 << 9 | 0x22;
else
vcpu_cp15(vcpu, c5_IFSR) = 2;
} else { /* !iabt */
/* Set DFAR and DFSR */
vcpu_cp15(vcpu, c6_DFAR) = addr;
is_lpae = (vcpu_cp15(vcpu, c2_TTBCR) >> 31);
/* Always give debug fault for now - should give guest a clue */
if (is_lpae)
vcpu_cp15(vcpu, c5_DFSR) = 1 << 9 | 0x22;
else
vcpu_cp15(vcpu, c5_DFSR) = 2;
}

}

/**
* kvm_inject_dabt - inject a data abort into the guest
* @vcpu: The VCPU to receive the undefined exception
* @addr: The address to report in the DFAR
*
* It is assumed that this code is called from the VCPU thread and that the
* VCPU therefore is not currently executing guest code.
*/
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
inject_abt(vcpu, false, addr);
}

/**
* kvm_inject_pabt - inject a prefetch abort into the guest
* @vcpu: The VCPU to receive the undefined exception
* @addr: The address to report in the DFAR
*
* It is assumed that this code is called from the VCPU thread and that the
* VCPU therefore is not currently executing guest code.
*/
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
inject_abt(vcpu, true, addr);
}

/**
* kvm_inject_vabt - inject an async abort / SError into the guest
* @vcpu: The VCPU to receive the exception
Expand Down
3 changes: 3 additions & 0 deletions arch/arm64/include/asm/kvm_emulate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,9 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu);
void kvm_inject_vabt(struct kvm_vcpu *vcpu);
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_undef32(struct kvm_vcpu *vcpu);
void kvm_inject_dabt32(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_inject_pabt32(struct kvm_vcpu *vcpu, unsigned long addr);

static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
{
Expand Down
74 changes: 3 additions & 71 deletions arch/arm64/kvm/inject_fault.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,74 +33,6 @@
#define LOWER_EL_AArch64_VECTOR 0x400
#define LOWER_EL_AArch32_VECTOR 0x600

static void prepare_fault32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset)
{
unsigned long cpsr;
unsigned long new_spsr_value = *vcpu_cpsr(vcpu);
bool is_thumb = (new_spsr_value & COMPAT_PSR_T_BIT);
u32 return_offset = (is_thumb) ? 4 : 0;
u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);

cpsr = mode | COMPAT_PSR_I_BIT;

if (sctlr & (1 << 30))
cpsr |= COMPAT_PSR_T_BIT;
if (sctlr & (1 << 25))
cpsr |= COMPAT_PSR_E_BIT;

*vcpu_cpsr(vcpu) = cpsr;

/* Note: These now point to the banked copies */
*vcpu_spsr(vcpu) = new_spsr_value;
*vcpu_reg32(vcpu, 14) = *vcpu_pc(vcpu) + return_offset;

/* Branch to exception vector */
if (sctlr & (1 << 13))
vect_offset += 0xffff0000;
else /* always have security exceptions */
vect_offset += vcpu_cp15(vcpu, c12_VBAR);

*vcpu_pc(vcpu) = vect_offset;
}

static void inject_undef32(struct kvm_vcpu *vcpu)
{
prepare_fault32(vcpu, COMPAT_PSR_MODE_UND, 4);
}

/*
* Modelled after TakeDataAbortException() and TakePrefetchAbortException
* pseudocode.
*/
static void inject_abt32(struct kvm_vcpu *vcpu, bool is_pabt,
unsigned long addr)
{
u32 vect_offset;
u32 *far, *fsr;
bool is_lpae;

if (is_pabt) {
vect_offset = 12;
far = &vcpu_cp15(vcpu, c6_IFAR);
fsr = &vcpu_cp15(vcpu, c5_IFSR);
} else { /* !iabt */
vect_offset = 16;
far = &vcpu_cp15(vcpu, c6_DFAR);
fsr = &vcpu_cp15(vcpu, c5_DFSR);
}

prepare_fault32(vcpu, COMPAT_PSR_MODE_ABT | COMPAT_PSR_A_BIT, vect_offset);

*far = addr;

/* Give the guest an IMPLEMENTATION DEFINED exception */
is_lpae = (vcpu_cp15(vcpu, c2_TTBCR) >> 31);
if (is_lpae)
*fsr = 1 << 9 | 0x34;
else
*fsr = 0x14;
}

enum exception_type {
except_type_sync = 0,
except_type_irq = 0x80,
Expand Down Expand Up @@ -197,7 +129,7 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
if (!(vcpu->arch.hcr_el2 & HCR_RW))
inject_abt32(vcpu, false, addr);
kvm_inject_dabt32(vcpu, addr);
else
inject_abt64(vcpu, false, addr);
}
Expand All @@ -213,7 +145,7 @@ void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
if (!(vcpu->arch.hcr_el2 & HCR_RW))
inject_abt32(vcpu, true, addr);
kvm_inject_pabt32(vcpu, addr);
else
inject_abt64(vcpu, true, addr);
}
Expand All @@ -227,7 +159,7 @@ void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
void kvm_inject_undefined(struct kvm_vcpu *vcpu)
{
if (!(vcpu->arch.hcr_el2 & HCR_RW))
inject_undef32(vcpu);
kvm_inject_undef32(vcpu);
else
inject_undef64(vcpu);
}
Expand Down
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