Re: [GIT PULL] KVM: x86: Emulated MMIO changes for 7.1

[Paolo Bonzini]

On Sat, Apr 11, 2026 at 1:58 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Emulated MMIO changes to fix a use-after-free (kernel stack) bug, and do a
> spring cleaning of the code (though it could certainly use even more cleaning).
>
> The following changes since commit 11439c4635edd669ae435eec308f4ab8a0804808:
>
>   Linux 7.0-rc2 (2026-03-01 15:39:31 -0800)
>
> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-mmio-7.1
>
> for you to fetch changes up to e2138c4a5be1e50d75281136bdc3e709cb07ec5e:
>
>   KVM: x86: Add helpers to prepare kvm_run for userspace MMIO exit (2026-03-02 16:06:49 -0800)
>
> ----------------------------------------------------------------
> KVM x86 emulated MMIO changes for 7.1
>
> Copy single-chunk MMIO write values into a persistent (per-fragment) field to
> fix use-after-free stack bugs due to KVM dereferencing a stack pointer after an
> exit to userspace.
>
> Clean up and comment the emulated MMIO code to try to make it easier to
> maintain (not necessarily "easy", but "easier").

Pulled, thanks.

Paolo

> ----------------------------------------------------------------
> Sean Christopherson (14):
>       KVM: x86: Use scratch field in MMIO fragment to hold small write values
>       KVM: x86: Open code handling of completed MMIO reads in emulator_read_write()
>       KVM: x86: Trace unsatisfied MMIO reads on a per-page basis
>       KVM: x86: Use local MMIO fragment variable to clean up emulator_read_write()
>       KVM: x86: Open code read vs. write userspace MMIO exits in emulator_read_write()
>       KVM: x86: Move MMIO write tracing into vcpu_mmio_write()
>       KVM: x86: Harden SEV-ES MMIO against on-stack use-after-free
>       KVM: x86: Dedup kvm_sev_es_mmio_{read,write}()
>       KVM: x86: Consolidate SEV-ES MMIO emulation into a single public API
>       KVM: x86: Bury emulator read/write ops in emulator_{read,write}_emulated()
>       KVM: x86: Fold emulator_write_phys() into write_emulate()
>       KVM: x86: Rename .read_write_emulate() to .read_write_guest()
>       KVM: x86: Don't panic the kernel if completing userspace I/O / MMIO goes sideways
>       KVM: x86: Add helpers to prepare kvm_run for userspace MMIO exit
>
>  arch/x86/include/asm/kvm_host.h |   3 -
>  arch/x86/kvm/emulate.c          |  13 ++
>  arch/x86/kvm/svm/sev.c          |  20 +--
>  arch/x86/kvm/vmx/tdx.c          |  14 +-
>  arch/x86/kvm/x86.c              | 287 ++++++++++++++++++----------------------
>  arch/x86/kvm/x86.h              |  32 ++++-
>  include/linux/kvm_host.h        |   3 +-
>  7 files changed, 180 insertions(+), 192 deletions(-)
>