[PATCH 0/8] KVM: SEV-ES: fixes for string I/O emulation

Paolo Bonzini
2021-10-13T16:56:27Z

This series, namely patches 1 and 8, fix two bugs in string I/O
emulation for SEV-ES:

- first, the length is completely off for "rep ins" and "rep outs"
operation of size > 1. After setup_vmgexit_scratch, svm->ghcb_sa_len
is in bytes, but kvm_sev_es_string_io expects the number of PIO
operations.

- second, the size of the GHCB buffer can exceed the size of
vcpu->arch.pio_data. If that happens, we need to go over the GHCB
buffer in multiple passes.

The second bug was reported by Felix Wilhelm. The first was found by
me by code inspection; on one hand it seems *too* egregious so I'll be
gladly proven wrong on this, on the other hand... I know I'm bad at code
review, but not _that_ bad.

Patches 2 to 7 are a bunch of cleanups to emulator_pio_in and
emulator_pio_in_out, so that the final SEV code is a little easier
to reason on. Just a little, no big promises.

Tested by booting a SEV-ES guest and with "regular" kvm-unit-tests.
For SEV-ES I also bounded the limit to 12 bytes, and checked in the
resulting trace that both the read and write paths were hit when
booting a guest.

Paolo

Paolo Bonzini (8):
KVM: SEV-ES: fix length of string I/O
KVM: SEV-ES: rename guest_ins_data to sev_pio_data
KVM: x86: leave vcpu->arch.pio.count alone in emulator_pio_in_out
KVM: SEV-ES: clean up kvm_sev_es_ins/outs
KVM: x86: split the two parts of emulator_pio_in
KVM: x86: remove unnecessary arguments from complete_emulator_pio_in
KVM: SEV-ES: keep INS functions together
KVM: SEV-ES: go over the sev_pio_data buffer in multiple passes if
needed

arch/x86/include/asm/kvm_host.h | 3 +-
arch/x86/kvm/svm/sev.c | 2 +-
arch/x86/kvm/x86.c | 136 +++++++++++++++++++++-----------
3 files changed, 95 insertions(+), 46 deletions(-)

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2.27.0