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KVM/arm64 fixes for 6.14, take #3

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- Fix TCR_EL2 configuration to not use the ASID in TTBR1_EL2
   and not mess-up T1SZ/PS by using the HCR_EL2.E2H==0 layout.
 
 - Bring back the VMID allocation to the vcpu_load phase, ensuring
   that we only setup VTTBR_EL2 once on VHE. This cures an ugly
   race that would lead to running with an unallocated VMID.
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Merge tag 'kvmarm-fixes-6.14-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

KVM/arm64 fixes for 6.14, take #3

- Fix TCR_EL2 configuration to not use the ASID in TTBR1_EL2
  and not mess-up T1SZ/PS by using the HCR_EL2.E2H==0 layout.

- Bring back the VMID allocation to the vcpu_load phase, ensuring
  that we only setup VTTBR_EL2 once on VHE. This cures an ugly
  race that would lead to running with an unallocated VMID.
This commit is contained in:
Paolo Bonzini 2025-02-24 13:20:00 -05:00
commit 4647c82276
4 changed files with 22 additions and 30 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
arch/arm64/include/asm/kvm_arm.h
View file

@ -119,7 +119,7 @@
#define TCR_EL2_IRGN0_MASK TCR_IRGN0_MASK
#define TCR_EL2_T0SZ_MASK 0x3f
#define TCR_EL2_MASK (TCR_EL2_TG0_MASK | TCR_EL2_SH0_MASK | \
TCR_EL2_ORGN0_MASK | TCR_EL2_IRGN0_MASK | TCR_EL2_T0SZ_MASK)
TCR_EL2_ORGN0_MASK | TCR_EL2_IRGN0_MASK)
/* VTCR_EL2 Registers bits */
#define VTCR_EL2_DS TCR_EL2_DS

2
arch/arm64/include/asm/kvm_host.h
View file

@ -1259,7 +1259,7 @@ int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu,
extern unsigned int __ro_after_init kvm_arm_vmid_bits;
int __init kvm_arm_vmid_alloc_init(void);
void __init kvm_arm_vmid_alloc_free(void);
bool kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid);
void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid);
void kvm_arm_vmid_clear_active(void);
static inline void kvm_arm_pvtime_vcpu_init(struct kvm_vcpu_arch *vcpu_arch)

37
arch/arm64/kvm/arm.c
View file

@ -559,6 +559,16 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
mmu = vcpu->arch.hw_mmu;
last_ran = this_cpu_ptr(mmu->last_vcpu_ran);
/*
* Ensure a VMID is allocated for the MMU before programming VTTBR_EL2,
* which happens eagerly in VHE.
*
* Also, the VMID allocator only preserves VMIDs that are active at the
* time of rollover, so KVM might need to grab a new VMID for the MMU if
* this is called from kvm_sched_in().
*/
kvm_arm_vmid_update(&mmu->vmid);
/*
* We guarantee that both TLBs and I-cache are private to each
* vcpu. If detecting that a vcpu from the same VM has
@ -1138,18 +1148,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
*/
preempt_disable();
/*
* The VMID allocator only tracks active VMIDs per
* physical CPU, and therefore the VMID allocated may not be
* preserved on VMID roll-over if the task was preempted,
* making a thread's VMID inactive. So we need to call
* kvm_arm_vmid_update() in non-premptible context.
*/
if (kvm_arm_vmid_update(&vcpu->arch.hw_mmu->vmid) &&
has_vhe())
__load_stage2(vcpu->arch.hw_mmu,
vcpu->arch.hw_mmu->arch);
kvm_pmu_flush_hwstate(vcpu);
local_irq_disable();
@ -1980,7 +1978,7 @@ static int kvm_init_vector_slots(void)
static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
{
struct kvm_nvhe_init_params *params = per_cpu_ptr_nvhe_sym(kvm_init_params, cpu);
unsigned long tcr, ips;
unsigned long tcr;
/*
* Calculate the raw per-cpu offset without a translation from the
@ -1994,19 +1992,18 @@ static void __init cpu_prepare_hyp_mode(int cpu, u32 hyp_va_bits)
params->mair_el2 = read_sysreg(mair_el1);
tcr = read_sysreg(tcr_el1);
ips = FIELD_GET(TCR_IPS_MASK, tcr);
if (cpus_have_final_cap(ARM64_KVM_HVHE)) {
tcr &= ~(TCR_HD | TCR_HA | TCR_A1 | TCR_T0SZ_MASK);
tcr |= TCR_EPD1_MASK;
} else {
unsigned long ips = FIELD_GET(TCR_IPS_MASK, tcr);
tcr &= TCR_EL2_MASK;
tcr |= TCR_EL2_RES1;
tcr |= TCR_EL2_RES1 | FIELD_PREP(TCR_EL2_PS_MASK, ips);
if (lpa2_is_enabled())
tcr |= TCR_EL2_DS;
}
tcr &= ~TCR_T0SZ_MASK;
tcr |= TCR_T0SZ(hyp_va_bits);
tcr &= ~TCR_EL2_PS_MASK;
tcr |= FIELD_PREP(TCR_EL2_PS_MASK, ips);
if (lpa2_is_enabled())
tcr |= TCR_EL2_DS;
params->tcr_el2 = tcr;
params->pgd_pa = kvm_mmu_get_httbr();

11
arch/arm64/kvm/vmid.c
View file

@ -135,11 +135,10 @@ void kvm_arm_vmid_clear_active(void)
atomic64_set(this_cpu_ptr(&active_vmids), VMID_ACTIVE_INVALID);
}
bool kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
{
unsigned long flags;
u64 vmid, old_active_vmid;
bool updated = false;
vmid = atomic64_read(&kvm_vmid->id);
@ -157,21 +156,17 @@ bool kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
if (old_active_vmid != 0 && vmid_gen_match(vmid) &&
0 != atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),
old_active_vmid, vmid))
return false;
return;
raw_spin_lock_irqsave(&cpu_vmid_lock, flags);
/* Check that our VMID belongs to the current generation. */
vmid = atomic64_read(&kvm_vmid->id);
if (!vmid_gen_match(vmid)) {
if (!vmid_gen_match(vmid))
vmid = new_vmid(kvm_vmid);
updated = true;
}
atomic64_set(this_cpu_ptr(&active_vmids), vmid);
raw_spin_unlock_irqrestore(&cpu_vmid_lock, flags);
return updated;
}
/*