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linux_dsm_epyc7002/arch/arm64/kvm/handle_exit.c
Mark Rutland ba4dd156ea arm64: KVM: Survive unknown traps from guests 
Currently we BUG() if we see an ESR_EL2.EC value we don't recognise. As
configurable disables/enables are added to the architecture (controlled
by RES1/RES0 bits respectively), with associated synchronous exceptions,
it may be possible for a guest to trigger exceptions with classes that
we don't recognise.

While we can't service these exceptions in a manner useful to the guest,
we can avoid bringing down the host. Per ARM DDI 0487A.k_iss10775, page
D7-1937, EC values within the range 0x00 - 0x2c are reserved for future
use with synchronous exceptions, and EC values within the range 0x2d -
0x3f may be used for either synchronous or asynchronous exceptions.

The patch makes KVM handle any unknown EC by injecting an UNDEFINED
exception into the guest, with a corresponding (ratelimited) warning in
the host dmesg. We could later improve on this with with a new (opt-in)
exit to the host userspace.

Cc: Dave Martin <dave.martin@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2017-03-07 14:50:46 +00:00

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/*
* Copyright (C) 2012,2013 - ARM Ltd
* Author: Marc Zyngier <marc.zyngier@arm.com>
*
* Derived from arch/arm/kvm/handle_exit.c:
* Copyright (C) 2012 - Virtual Open Systems and Columbia University
* Author: Christoffer Dall <c.dall@virtualopensystems.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <asm/esr.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_coproc.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_mmu.h>
#include <asm/kvm_psci.h>
#define CREATE_TRACE_POINTS
#include "trace.h"
typedef int (*exit_handle_fn)(struct kvm_vcpu *, struct kvm_run *);
static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
int ret;
trace_kvm_hvc_arm64(*vcpu_pc(vcpu), vcpu_get_reg(vcpu, 0),
kvm_vcpu_hvc_get_imm(vcpu));
vcpu->stat.hvc_exit_stat++;
ret = kvm_psci_call(vcpu);
if (ret < 0) {
kvm_inject_undefined(vcpu);
return 1;
}
return ret;
}
static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
kvm_inject_undefined(vcpu);
return 1;
}
/*
* Guest access to FP/ASIMD registers are routed to this handler only
* when the system doesn't support FP/ASIMD.
*/
static int handle_no_fpsimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
kvm_inject_undefined(vcpu);
return 1;
}
/**
* kvm_handle_wfx - handle a wait-for-interrupts or wait-for-event
* instruction executed by a guest
*
* @vcpu: the vcpu pointer
*
* WFE: Yield the CPU and come back to this vcpu when the scheduler
* decides to.
* WFI: Simply call kvm_vcpu_block(), which will halt execution of
* world-switches and schedule other host processes until there is an
* incoming IRQ or FIQ to the VM.
*/
static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
vcpu->stat.wfe_exit_stat++;
kvm_vcpu_on_spin(vcpu);
} else {
trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
vcpu->stat.wfi_exit_stat++;
kvm_vcpu_block(vcpu);
}
kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
return 1;
}
/**
* kvm_handle_guest_debug - handle a debug exception instruction
*
* @vcpu: the vcpu pointer
* @run: access to the kvm_run structure for results
*
* We route all debug exceptions through the same handler. If both the
* guest and host are using the same debug facilities it will be up to
* userspace to re-inject the correct exception for guest delivery.
*
* @return: 0 (while setting run->exit_reason), -1 for error
*/
static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
u32 hsr = kvm_vcpu_get_hsr(vcpu);
int ret = 0;
run->exit_reason = KVM_EXIT_DEBUG;
run->debug.arch.hsr = hsr;
switch (ESR_ELx_EC(hsr)) {
case ESR_ELx_EC_WATCHPT_LOW:
run->debug.arch.far = vcpu->arch.fault.far_el2;
/* fall through */
case ESR_ELx_EC_SOFTSTP_LOW:
case ESR_ELx_EC_BREAKPT_LOW:
case ESR_ELx_EC_BKPT32:
case ESR_ELx_EC_BRK64:
break;
default:
kvm_err("%s: un-handled case hsr: %#08x\n",
__func__, (unsigned int) hsr);
ret = -1;
break;
}
return ret;
}
static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
u32 hsr = kvm_vcpu_get_hsr(vcpu);
kvm_pr_unimpl("Unknown exception class: hsr: %#08x -- %s\n",
hsr, esr_get_class_string(hsr));
kvm_inject_undefined(vcpu);
return 1;
}
static exit_handle_fn arm_exit_handlers[] = {
[0 ... ESR_ELx_EC_MAX] = kvm_handle_unknown_ec,
[ESR_ELx_EC_WFx] = kvm_handle_wfx,
[ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32,
[ESR_ELx_EC_CP15_64] = kvm_handle_cp15_64,
[ESR_ELx_EC_CP14_MR] = kvm_handle_cp14_32,
[ESR_ELx_EC_CP14_LS] = kvm_handle_cp14_load_store,
[ESR_ELx_EC_CP14_64] = kvm_handle_cp14_64,
[ESR_ELx_EC_HVC32] = handle_hvc,
[ESR_ELx_EC_SMC32] = handle_smc,
[ESR_ELx_EC_HVC64] = handle_hvc,
[ESR_ELx_EC_SMC64] = handle_smc,
[ESR_ELx_EC_SYS64] = kvm_handle_sys_reg,
[ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort,
[ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort,
[ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_WATCHPT_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug,
[ESR_ELx_EC_BRK64] = kvm_handle_guest_debug,
[ESR_ELx_EC_FP_ASIMD] = handle_no_fpsimd,
};
static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
{
u32 hsr = kvm_vcpu_get_hsr(vcpu);
u8 hsr_ec = ESR_ELx_EC(hsr);
return arm_exit_handlers[hsr_ec];
}
/*
* Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
* proper exit to userspace.
*/
int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
int exception_index)
{
exit_handle_fn exit_handler;
if (ARM_SERROR_PENDING(exception_index)) {
u8 hsr_ec = ESR_ELx_EC(kvm_vcpu_get_hsr(vcpu));
/*
* HVC/SMC already have an adjusted PC, which we need
* to correct in order to return to after having
* injected the SError.
*/
if (hsr_ec == ESR_ELx_EC_HVC32 || hsr_ec == ESR_ELx_EC_HVC64 ||
hsr_ec == ESR_ELx_EC_SMC32 || hsr_ec == ESR_ELx_EC_SMC64) {
u32 adj = kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
*vcpu_pc(vcpu) -= adj;
}
kvm_inject_vabt(vcpu);
return 1;
}
exception_index = ARM_EXCEPTION_CODE(exception_index);
switch (exception_index) {
case ARM_EXCEPTION_IRQ:
return 1;
case ARM_EXCEPTION_EL1_SERROR:
kvm_inject_vabt(vcpu);
return 1;
case ARM_EXCEPTION_TRAP:
/*
* See ARM ARM B1.14.1: "Hyp traps on instructions
* that fail their condition code check"
*/
if (!kvm_condition_valid(vcpu)) {
kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
return 1;
}
exit_handler = kvm_get_exit_handler(vcpu);
return exit_handler(vcpu, run);
case ARM_EXCEPTION_HYP_GONE:
/*
* EL2 has been reset to the hyp-stub. This happens when a guest
* is pre-empted by kvm_reboot()'s shutdown call.
*/
run->exit_reason = KVM_EXIT_FAIL_ENTRY;
return 0;
default:
kvm_pr_unimpl("Unsupported exception type: %d",
exception_index);
run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
return 0;
}
}
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