---
id: CVE-2026-98715
title: 'KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN

  Don't reset the VMCB's TLB control back to "do nothing" on a failed VMRUN,
  as empirical testing…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f <
    fd873c3d1b5240e80365f09e758e8c96b88a7cdb
  - >-
    Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f <
    60d93c27859fb3ec5b5a689e24de303f166477d0
  - Linux 2.6.38
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:46:47.988Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98715'
references:
  - url: 'https://git.kernel.org/stable/c/fd873c3d1b5240e80365f09e758e8c96b88a7cdb'
  - url: 'https://git.kernel.org/stable/c/60d93c27859fb3ec5b5a689e24de303f166477d0'
tags:
  - cve.org
ingestedAt: '2026-10-18T16:47:32.511Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN

Don't reset the VMCB's TLB control back to "do nothing" on a failed VMRUN,
as empirical testing shows that the CPU performs the requested TLB flush if
and only if VMRUN is successful, i.e. clearing TLB control on a failed
VMRUN effectively drops a TLB flush.

Explicitly track the need to flush all ASIDs on a per-CPU basis, as the
ASID reuse condition is tied to the pCPU, not to the vCPU.  As a bonus,
this also obviates the need to avoid clobbering FLUSH_ALL_ASID with
TLB_CONTROL_FLUSH_ASID, e.g. in svm_flush_tlb_asid().

Deliberately don't bother saving/restoring the "old" tlb_ctl on failure,
in quotes because it's not exactly the old tlb_ctl, it's the tlb_ctl from
after pre_svm_run(), but before updating tlb_ctl for flush_all_asids.  If
VMRUN fails and TLB_CONTROL_FLUSH_ALL_ASID is forced, then the next
successful run of the VMCB *may* unnecessarily flush all ASIDs, which
strictly speaking could result in noisy neighbor issues.  However, the
fact that new_asid() is already guest-triggerable, because of KVM's flawed
behavior of clearing the ASID on emulated INIT, means that a guest can
already trigger a flush of all ASIDs at roughly the same rate.  And once
KVM stops clobbering the ASID on emulated INIT, *or* assigns a static ASID
to each vCPU, this flaw goes away.

## Affected

- `Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < fd873c3d1b5240e80365f09e758e8c96b88a7cdb`
- `Linux >= 38e5e92fe8c02a8766459d505423b855caf9af1f < 60d93c27859fb3ec5b5a689e24de303f166477d0`
- `Linux 2.6.38`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.