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linux_dsm_epyc7002/arch/arm64/include/asm/kvm_emulate.h
Will Deacon 60e21a0ef5 arm64: KVM: Take S1 walks into account when determining S2 write faults 
The WnR bit in the HSR/ESR_EL2 indicates whether a data abort was
generated by a read or a write instruction. For stage 2 data aborts
generated by a stage 1 translation table walk (i.e. the actual page
table access faults at EL2), the WnR bit therefore reports whether the
instruction generating the walk was a load or a store, *not* whether the
page table walker was reading or writing the entry.

For page tables marked as read-only at stage 2 (e.g. due to KSM merging
them with the tables from another guest), this could result in livelock,
where a page table walk generated by a load instruction attempts to
set the access flag in the stage 1 descriptor, but fails to trigger
CoW in the host since only a read fault is reported.

This patch modifies the arm64 kvm_vcpu_dabt_iswrite function to
take into account stage 2 faults in stage 1 walks. Since DBM cannot be
disabled at EL2 for CPUs that implement it, we assume that these faults
are always causes by writes, avoiding the livelock situation at the
expense of occasional, spurious CoWs.

We could, in theory, do a bit better by checking the guest TCR
configuration and inspecting the page table to see why the PTE faulted.
However, I doubt this is measurable in practice, and the threat of
livelock is real.

Cc: <stable@vger.kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-10-21 17:25:47 +01:00

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/*
* Copyright (C) 2012,2013 - ARM Ltd
* Author: Marc Zyngier <marc.zyngier@arm.com>
*
* Derived from arch/arm/include/kvm_emulate.h
* 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/>.
*/
#ifndef __ARM64_KVM_EMULATE_H__
#define __ARM64_KVM_EMULATE_H__
#include <linux/kvm_host.h>
#include <asm/esr.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_mmio.h>
#include <asm/ptrace.h>
#include <asm/cputype.h>
#include <asm/virt.h>
unsigned long *vcpu_reg32(const struct kvm_vcpu *vcpu, u8 reg_num);
unsigned long *vcpu_spsr32(const struct kvm_vcpu *vcpu);
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_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 vcpu_reset_hcr(struct kvm_vcpu *vcpu)
{
vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;
if (is_kernel_in_hyp_mode())
vcpu->arch.hcr_el2 |= HCR_E2H;
if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features))
vcpu->arch.hcr_el2 &= ~HCR_RW;
}
static inline unsigned long vcpu_get_hcr(struct kvm_vcpu *vcpu)
{
return vcpu->arch.hcr_el2;
}
static inline void vcpu_set_hcr(struct kvm_vcpu *vcpu, unsigned long hcr)
{
vcpu->arch.hcr_el2 = hcr;
}
static inline unsigned long *vcpu_pc(const struct kvm_vcpu *vcpu)
{
return (unsigned long *)&vcpu_gp_regs(vcpu)->regs.pc;
}
static inline unsigned long *vcpu_elr_el1(const struct kvm_vcpu *vcpu)
{
return (unsigned long *)&vcpu_gp_regs(vcpu)->elr_el1;
}
static inline unsigned long *vcpu_cpsr(const struct kvm_vcpu *vcpu)
{
return (unsigned long *)&vcpu_gp_regs(vcpu)->regs.pstate;
}
static inline bool vcpu_mode_is_32bit(const struct kvm_vcpu *vcpu)
{
return !!(*vcpu_cpsr(vcpu) & PSR_MODE32_BIT);
}
static inline bool kvm_condition_valid(const struct kvm_vcpu *vcpu)
{
if (vcpu_mode_is_32bit(vcpu))
return kvm_condition_valid32(vcpu);
return true;
}
static inline void kvm_skip_instr(struct kvm_vcpu *vcpu, bool is_wide_instr)
{
if (vcpu_mode_is_32bit(vcpu))
kvm_skip_instr32(vcpu, is_wide_instr);
else
*vcpu_pc(vcpu) += 4;
}
static inline void vcpu_set_thumb(struct kvm_vcpu *vcpu)
{
*vcpu_cpsr(vcpu) |= COMPAT_PSR_T_BIT;
}
/*
* vcpu_get_reg and vcpu_set_reg should always be passed a register number
* coming from a read of ESR_EL2. Otherwise, it may give the wrong result on
* AArch32 with banked registers.
*/
static inline unsigned long vcpu_get_reg(const struct kvm_vcpu *vcpu,
u8 reg_num)
{
return (reg_num == 31) ? 0 : vcpu_gp_regs(vcpu)->regs.regs[reg_num];
}
static inline void vcpu_set_reg(struct kvm_vcpu *vcpu, u8 reg_num,
unsigned long val)
{
if (reg_num != 31)
vcpu_gp_regs(vcpu)->regs.regs[reg_num] = val;
}
/* Get vcpu SPSR for current mode */
static inline unsigned long *vcpu_spsr(const struct kvm_vcpu *vcpu)
{
if (vcpu_mode_is_32bit(vcpu))
return vcpu_spsr32(vcpu);
return (unsigned long *)&vcpu_gp_regs(vcpu)->spsr[KVM_SPSR_EL1];
}
static inline bool vcpu_mode_priv(const struct kvm_vcpu *vcpu)
{
u32 mode;
if (vcpu_mode_is_32bit(vcpu)) {
mode = *vcpu_cpsr(vcpu) & COMPAT_PSR_MODE_MASK;
return mode > COMPAT_PSR_MODE_USR;
}
mode = *vcpu_cpsr(vcpu) & PSR_MODE_MASK;
return mode != PSR_MODE_EL0t;
}
static inline u32 kvm_vcpu_get_hsr(const struct kvm_vcpu *vcpu)
{
return vcpu->arch.fault.esr_el2;
}
static inline int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
{
u32 esr = kvm_vcpu_get_hsr(vcpu);
if (esr & ESR_ELx_CV)
return (esr & ESR_ELx_COND_MASK) >> ESR_ELx_COND_SHIFT;
return -1;
}
static inline unsigned long kvm_vcpu_get_hfar(const struct kvm_vcpu *vcpu)
{
return vcpu->arch.fault.far_el2;
}
static inline phys_addr_t kvm_vcpu_get_fault_ipa(const struct kvm_vcpu *vcpu)
{
return ((phys_addr_t)vcpu->arch.fault.hpfar_el2 & HPFAR_MASK) << 8;
}
static inline u32 kvm_vcpu_hvc_get_imm(const struct kvm_vcpu *vcpu)
{
return kvm_vcpu_get_hsr(vcpu) & ESR_ELx_xVC_IMM_MASK;
}
static inline bool kvm_vcpu_dabt_isvalid(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_ISV);
}
static inline bool kvm_vcpu_dabt_issext(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SSE);
}
static inline int kvm_vcpu_dabt_get_rd(const struct kvm_vcpu *vcpu)
{
return (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT;
}
static inline bool kvm_vcpu_dabt_isextabt(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_EA);
}
static inline bool kvm_vcpu_dabt_iss1tw(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_S1PTW);
}
static inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WNR) ||
kvm_vcpu_dabt_iss1tw(vcpu); /* AF/DBM update */
}
static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_CM);
}
static inline int kvm_vcpu_dabt_get_as(const struct kvm_vcpu *vcpu)
{
return 1 << ((kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SAS) >> ESR_ELx_SAS_SHIFT);
}
/* This one is not specific to Data Abort */
static inline bool kvm_vcpu_trap_il_is32bit(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_IL);
}
static inline u8 kvm_vcpu_trap_get_class(const struct kvm_vcpu *vcpu)
{
return ESR_ELx_EC(kvm_vcpu_get_hsr(vcpu));
}
static inline bool kvm_vcpu_trap_is_iabt(const struct kvm_vcpu *vcpu)
{
return kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_IABT_LOW;
}
static inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
{
return kvm_vcpu_get_hsr(vcpu) & ESR_ELx_FSC;
}
static inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vcpu)
{
return kvm_vcpu_get_hsr(vcpu) & ESR_ELx_FSC_TYPE;
}
static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
{
return vcpu_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
}
static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
{
if (vcpu_mode_is_32bit(vcpu))
*vcpu_cpsr(vcpu) |= COMPAT_PSR_E_BIT;
else
vcpu_sys_reg(vcpu, SCTLR_EL1) |= (1 << 25);
}
static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
{
if (vcpu_mode_is_32bit(vcpu))
return !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_E_BIT);
return !!(vcpu_sys_reg(vcpu, SCTLR_EL1) & (1 << 25));
}
static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
unsigned long data,
unsigned int len)
{
if (kvm_vcpu_is_be(vcpu)) {
switch (len) {
case 1:
return data & 0xff;
case 2:
return be16_to_cpu(data & 0xffff);
case 4:
return be32_to_cpu(data & 0xffffffff);
default:
return be64_to_cpu(data);
}
} else {
switch (len) {
case 1:
return data & 0xff;
case 2:
return le16_to_cpu(data & 0xffff);
case 4:
return le32_to_cpu(data & 0xffffffff);
default:
return le64_to_cpu(data);
}
}
return data; /* Leave LE untouched */
}
static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
unsigned long data,
unsigned int len)
{
if (kvm_vcpu_is_be(vcpu)) {
switch (len) {
case 1:
return data & 0xff;
case 2:
return cpu_to_be16(data & 0xffff);
case 4:
return cpu_to_be32(data & 0xffffffff);
default:
return cpu_to_be64(data);
}
} else {
switch (len) {
case 1:
return data & 0xff;
case 2:
return cpu_to_le16(data & 0xffff);
case 4:
return cpu_to_le32(data & 0xffffffff);
default:
return cpu_to_le64(data);
}
}
return data; /* Leave LE untouched */
}
#endif /* __ARM64_KVM_EMULATE_H__ */
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