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arm64: KVM: Move most of the fault decoding to C 

The fault decoding process (including computing the IPA in the case
of a permission fault) would be much better done in C code, as we
have a reasonable infrastructure to deal with the VHE/non-VHE
differences.

Let's move the whole thing to C, including the workaround for
erratum 834220, and just patch the odd ESR_EL2 access remaining
in hyp-entry.S.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Marc Zyngier 2015-10-28 15:06:47 +00:00
parent 253dcbd39a
commit 5f05a72aed
3 changed files with 90 additions and 67 deletions
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3
arch/arm64/kernel/asm-offsets.c
View File

@ -110,9 +110,6 @@ int main(void)
DEFINE(CPU_USER_PT_REGS, offsetof(struct kvm_regs, regs));
DEFINE(CPU_FP_REGS, offsetof(struct kvm_regs, fp_regs));
DEFINE(VCPU_FPEXC32_EL2, offsetof(struct kvm_vcpu, arch.ctxt.sys_regs[FPEXC32_EL2]));
DEFINE(VCPU_ESR_EL2, offsetof(struct kvm_vcpu, arch.fault.esr_el2));
DEFINE(VCPU_FAR_EL2, offsetof(struct kvm_vcpu, arch.fault.far_el2));
DEFINE(VCPU_HPFAR_EL2, offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
#endif
#ifdef CONFIG_CPU_PM

69
arch/arm64/kvm/hyp/hyp-entry.S
View File

@ -19,7 +19,6 @@
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/cpufeature.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_asm.h>
@ -69,7 +68,11 @@ ENDPROC(__vhe_hyp_call)
el1_sync: // Guest trapped into EL2
save_x0_to_x3
alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
mrs x1, esr_el2
alternative_else
mrs x1, esr_el1
alternative_endif
lsr x2, x1, #ESR_ELx_EC_SHIFT
cmp x2, #ESR_ELx_EC_HVC64
@ -105,72 +108,10 @@ el1_trap:
cmp x2, #ESR_ELx_EC_FP_ASIMD
b.eq __fpsimd_guest_restore
cmp x2, #ESR_ELx_EC_DABT_LOW
mov x0, #ESR_ELx_EC_IABT_LOW
ccmp x2, x0, #4, ne
b.ne 1f // Not an abort we care about
/* This is an abort. Check for permission fault */
alternative_if_not ARM64_WORKAROUND_834220
and x2, x1, #ESR_ELx_FSC_TYPE
cmp x2, #FSC_PERM
b.ne 1f // Not a permission fault
alternative_else
nop // Use the permission fault path to
nop // check for a valid S1 translation,
nop // regardless of the ESR value.
alternative_endif
/*
* Check for Stage-1 page table walk, which is guaranteed
* to give a valid HPFAR_EL2.
*/
tbnz x1, #7, 1f // S1PTW is set
/* Preserve PAR_EL1 */
mrs x3, par_el1
stp x3, xzr, [sp, #-16]!
/*
* Permission fault, HPFAR_EL2 is invalid.
* Resolve the IPA the hard way using the guest VA.
* Stage-1 translation already validated the memory access rights.
* As such, we can use the EL1 translation regime, and don't have
* to distinguish between EL0 and EL1 access.
*/
mrs x2, far_el2
at s1e1r, x2
isb
/* Read result */
mrs x3, par_el1
ldp x0, xzr, [sp], #16 // Restore PAR_EL1 from the stack
msr par_el1, x0
tbnz x3, #0, 3f // Bail out if we failed the translation
ubfx x3, x3, #12, #36 // Extract IPA
lsl x3, x3, #4 // and present it like HPFAR
b 2f
1: mrs x3, hpfar_el2
mrs x2, far_el2
2: mrs x0, tpidr_el2
str w1, [x0, #VCPU_ESR_EL2]
str x2, [x0, #VCPU_FAR_EL2]
str x3, [x0, #VCPU_HPFAR_EL2]
mrs x0, tpidr_el2
mov x1, #ARM_EXCEPTION_TRAP
b __guest_exit
/*
* Translation failed. Just return to the guest and
* let it fault again. Another CPU is probably playing
* behind our back.
*/
3: restore_x0_to_x3
eret
el1_irq:
save_x0_to_x3
mrs x0, tpidr_el2

85
arch/arm64/kvm/hyp/switch.c
View File

@ -15,6 +15,7 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/types.h>
#include <asm/kvm_asm.h>
#include "hyp.h"
@ -149,6 +150,86 @@ static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
__vgic_call_restore_state()(vcpu);
}
static bool __hyp_text __true_value(void)
{
return true;
}
static bool __hyp_text __false_value(void)
{
return false;
}
static hyp_alternate_select(__check_arm_834220,
__false_value, __true_value,
ARM64_WORKAROUND_834220);
static bool __hyp_text __translate_far_to_hpfar(u64 far, u64 *hpfar)
{
u64 par, tmp;
/*
* Resolve the IPA the hard way using the guest VA.
*
* Stage-1 translation already validated the memory access
* rights. As such, we can use the EL1 translation regime, and
* don't have to distinguish between EL0 and EL1 access.
*
* We do need to save/restore PAR_EL1 though, as we haven't
* saved the guest context yet, and we may return early...
*/
par = read_sysreg(par_el1);
asm volatile("at s1e1r, %0" : : "r" (far));
isb();
tmp = read_sysreg(par_el1);
write_sysreg(par, par_el1);
if (unlikely(tmp & 1))
return false; /* Translation failed, back to guest */
/* Convert PAR to HPFAR format */
*hpfar = ((tmp >> 12) & ((1UL << 36) - 1)) << 4;
return true;
}
static bool __hyp_text __populate_fault_info(struct kvm_vcpu *vcpu)
{
u64 esr = read_sysreg_el2(esr);
u8 ec = esr >> ESR_ELx_EC_SHIFT;
u64 hpfar, far;
vcpu->arch.fault.esr_el2 = esr;
if (ec != ESR_ELx_EC_DABT_LOW && ec != ESR_ELx_EC_IABT_LOW)
return true;
far = read_sysreg_el2(far);
/*
* The HPFAR can be invalid if the stage 2 fault did not
* happen during a stage 1 page table walk (the ESR_EL2.S1PTW
* bit is clear) and one of the two following cases are true:
* 1. The fault was due to a permission fault
* 2. The processor carries errata 834220
*
* Therefore, for all non S1PTW faults where we either have a
* permission fault or the errata workaround is enabled, we
* resolve the IPA using the AT instruction.
*/
if (!(esr & ESR_ELx_S1PTW) &&
(__check_arm_834220()() || (esr & ESR_ELx_FSC_TYPE) == FSC_PERM)) {
if (!__translate_far_to_hpfar(far, &hpfar))
return false;
} else {
hpfar = read_sysreg(hpfar_el2);
}
vcpu->arch.fault.far_el2 = far;
vcpu->arch.fault.hpfar_el2 = hpfar;
return true;
}
static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
{
struct kvm_cpu_context *host_ctxt;
@ -180,9 +261,13 @@ static int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
__debug_restore_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
/* Jump in the fire! */
again:
exit_code = __guest_enter(vcpu, host_ctxt);
/* And we're baaack! */
if (exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
goto again;
fp_enabled = __fpsimd_enabled();
__sysreg_save_guest_state(guest_ctxt);