[v5,00/10] Make PAT handling less brittle

Message

Demi Marie Obenour Dec. 20, 2022, 1:07 a.m. UTC

While working on Qubes OS Marek found out that there were some PAT hacks
in the Linux i195 driver.  I decided to make Xen use Linux’s PAT to see
if it solved the graphics glitches that were observed; it did.  This
required a substantial amount of preliminary work that is useful even
without using Linux’s PAT.

Patches 1 through 9 are the preliminary work and I would like them to be
accepted into upstream Xen.  Patch 9 does break ABI by rejecting the
unused PAT entries, but this will only impact buggy PV guests and can be
disabled with a Xen command-line option.  Patch 10 actually switches to
Linux’s PAT and is NOT intended to be merged (at least for now) as it
would at a minimum break migration of PV guests from hosts that do not
have the patch.

Only patches 9 and 10 actually change Xen’s observable behavior.
Patches 1, 2, and 7 are prerequisites, and patches 3 through 6 are
cleanups.  Patch 8 makes changing the PAT much less error-prone, as
problems with the PAT or with the associated _PAGE_* constants will
be detected at compile time.

Demi Marie Obenour (10):
  x86: Add memory type constants
  x86/mm: Avoid hard-coding PAT in get_page_from_l1e()
  x86: Replace PAT_* with X86_MT_*
  x86: Replace MTRR_* constants with X86_MT_* constants
  x86: Replace EPT_EMT_* constants with X86_MT_*
  x86: Remove MEMORY_NUM_TYPES and NO_HARDCODE_MEM_TYPE
  x86: Derive XEN_MSR_PAT from its individual entries
  x86/mm: make code robust to future PAT changes
  x86/mm: Reject invalid cacheability in PV guests by default
  x86: Use Linux's PAT

 xen/arch/x86/cpu/mtrr/generic.c         |  10 +-
 xen/arch/x86/cpu/mtrr/main.c            |  26 +++---
 xen/arch/x86/e820.c                     |   4 +-
 xen/arch/x86/hvm/hvm.c                  |  12 +--
 xen/arch/x86/hvm/mtrr.c                 | 100 ++++++++++----------
 xen/arch/x86/hvm/vmx/vmcs.c             |   2 +-
 xen/arch/x86/hvm/vmx/vmx.c              |  18 ++--
 xen/arch/x86/include/asm/hvm/vmx/vmcs.h |   2 +-
 xen/arch/x86/include/asm/hvm/vmx/vmx.h  |   9 --
 xen/arch/x86/include/asm/mtrr.h         |  22 +----
 xen/arch/x86/include/asm/page.h         |   4 +-
 xen/arch/x86/include/asm/processor.h    |  11 ++-
 xen/arch/x86/include/asm/x86-defns.h    |  11 +++
 xen/arch/x86/mm.c                       | 118 ++++++++++++++++++++++--
 xen/arch/x86/mm/hap/nested_ept.c        |   4 +-
 xen/arch/x86/mm/p2m-ept.c               |  51 +++++-----
 xen/arch/x86/mm/shadow/multi.c          |   8 +-
 17 files changed, 253 insertions(+), 159 deletions(-)