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KVM x86/mmu changes for 6.5:

Browse Source 
- Add back a comment about the subtle side effect of try_cmpxchg64() in
    tdp_mmu_set_spte_atomic()
 
  - Add an assertion in __kvm_mmu_invalidate_addr() to verify that the target
    KVM MMU is the current MMU
 
  - Add a "never" option to effectively avoid creating NX hugepage recovery
    threads
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Merge tag 'kvm-x86-mmu-6.5' of https://github.com/kvm-x86/linux into HEAD

KVM x86/mmu changes for 6.5:

 - Add back a comment about the subtle side effect of try_cmpxchg64() in
   tdp_mmu_set_spte_atomic()

 - Add an assertion in __kvm_mmu_invalidate_addr() to verify that the target
   KVM MMU is the current MMU

 - Add a "never" option to effectively avoid creating NX hugepage recovery
   threads
This commit is contained in:
Paolo Bonzini 2023-07-01 07:18:30 -04:00
commit 88de4b9480
2 changed files with 48 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
arch/x86/kvm/mmu/mmu.c
View File

@ -58,6 +58,8 @@
extern bool itlb_multihit_kvm_mitigation;
static bool nx_hugepage_mitigation_hard_disabled;
int __read_mostly nx_huge_pages = -1;
static uint __read_mostly nx_huge_pages_recovery_period_ms;
#ifdef CONFIG_PREEMPT_RT
@ -67,12 +69,13 @@ static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
#endif
static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp);
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp);
static const struct kernel_param_ops nx_huge_pages_ops = {
.set = set_nx_huge_pages,
.get = param_get_bool,
.get = get_nx_huge_pages,
};
static const struct kernel_param_ops nx_huge_pages_recovery_param_ops = {
@ -5797,6 +5800,14 @@ static void __kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu
vcpu_clear_mmio_info(vcpu, addr);
/*
* Walking and synchronizing SPTEs both assume they are operating in
* the context of the current MMU, and would need to be reworked if
* this is ever used to sync the guest_mmu, e.g. to emulate INVEPT.
*/
if (WARN_ON_ONCE(mmu != vcpu->arch.mmu))
return;
if (!VALID_PAGE(root_hpa))
return;
@ -6844,6 +6855,14 @@ static void mmu_destroy_caches(void)
kmem_cache_destroy(mmu_page_header_cache);
}
static int get_nx_huge_pages(char *buffer, const struct kernel_param *kp)
{
if (nx_hugepage_mitigation_hard_disabled)
return sprintf(buffer, "never\n");
return param_get_bool(buffer, kp);
}
static bool get_nx_auto_mode(void)
{
/* Return true when CPU has the bug, and mitigations are ON */
@ -6860,15 +6879,29 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
bool old_val = nx_huge_pages;
bool new_val;
if (nx_hugepage_mitigation_hard_disabled)
return -EPERM;
/* In "auto" mode deploy workaround only if CPU has the bug. */
if (sysfs_streq(val, "off"))
if (sysfs_streq(val, "off")) {
new_val = 0;
else if (sysfs_streq(val, "force"))
} else if (sysfs_streq(val, "force")) {
new_val = 1;
else if (sysfs_streq(val, "auto"))
} else if (sysfs_streq(val, "auto")) {
new_val = get_nx_auto_mode();
else if (kstrtobool(val, &new_val) < 0)
} else if (sysfs_streq(val, "never")) {
new_val = 0;
mutex_lock(&kvm_lock);
if (!list_empty(&vm_list)) {
mutex_unlock(&kvm_lock);
return -EBUSY;
}
nx_hugepage_mitigation_hard_disabled = true;
mutex_unlock(&kvm_lock);
} else if (kstrtobool(val, &new_val) < 0) {
return -EINVAL;
}
__set_nx_huge_pages(new_val);
@ -7006,6 +7039,9 @@ static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel
uint old_period, new_period;
int err;
if (nx_hugepage_mitigation_hard_disabled)
return -EPERM;
was_recovery_enabled = calc_nx_huge_pages_recovery_period(&old_period);
err = param_set_uint(val, kp);
@ -7164,6 +7200,9 @@ int kvm_mmu_post_init_vm(struct kvm *kvm)
{
int err;
if (nx_hugepage_mitigation_hard_disabled)
return 0;
err = kvm_vm_create_worker_thread(kvm, kvm_nx_huge_page_recovery_worker, 0,
"kvm-nx-lpage-recovery",
&kvm->arch.nx_huge_page_recovery_thread);

5
arch/x86/kvm/mmu/tdp_mmu.c
View File

@ -592,7 +592,10 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm,
/*
* Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs and
* does not hold the mmu_lock.
* does not hold the mmu_lock. On failure, i.e. if a different logical
* CPU modified the SPTE, try_cmpxchg64() updates iter->old_spte with
* the current value, so the caller operates on fresh data, e.g. if it
* retries tdp_mmu_set_spte_atomic()
*/
if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte))
return -EBUSY;