[v5,0/6] target/arm: Reduced-IPA space and highmem fixes

Message

Marc Zyngier Jan. 14, 2022, 2:07 p.m. UTC

Here's yet another stab at enabling QEMU on systems with
pathologically reduced IPA ranges such as the Apple M1 (previous
version at [1]). Eventually, we're able to run a KVM guest with more
than just 3GB of RAM on a system with a 36bit IPA space, and at most
123 vCPUs.

This also addresses some pathological QEMU behaviours, where the
highmem property is used as a flag allowing exposure of devices that
can't possibly fit in the PA space of the VM, resulting in a guest
failure.

In the end, we generalise the notion of PA space when exposing
individual devices in the expanded memory map, and treat highmem as
another flavour of PA space restriction.

This series does a few things:

- introduce new attributes to control the enabling of the highmem
  GICv3 redistributors and the highmem PCIe MMIO range

- correctly cap the PA range with highmem is off

- generalise the highmem behaviour to any PA range

- disable each highmem device region that doesn't fit in the PA range

- cleanup uses of highmem outside of virt_set_memmap()

This has been tested on an M1-based Mac-mini running Linux v5.16-rc6
with both KVM and TCG.

* From v4: [1]

  - Moved cpu_type_valid() check before we compute the memory map
  - Drop useless MAX() when computing highest_gpa
  - Fixed more deviations from the QEMU coding style
  - Collected Eric's RBs, with thanks

[1]: https://lore.kernel.org/r/[e-mail]

Marc Zyngier (6):
  hw/arm/virt: Add a control for the the highmem PCIe MMIO
  hw/arm/virt: Add a control for the the highmem redistributors
  hw/arm/virt: Honor highmem setting when computing the memory map
  hw/arm/virt: Use the PA range to compute the memory map
  hw/arm/virt: Disable highmem devices that don't fit in the PA range
  hw/arm/virt: Drop superfluous checks against highmem

 hw/arm/virt-acpi-build.c | 10 ++--
 hw/arm/virt.c            | 98 ++++++++++++++++++++++++++++++++++------
 include/hw/arm/virt.h    |  5 +-
 3 files changed, 91 insertions(+), 22 deletions(-)

Comments

Peter Maydell Jan. 18, 2022, 5:17 p.m. UTC | #1

On Fri, 14 Jan 2022 at 14:08, Marc Zyngier <[e-mail]> wrote:
>
> Here's yet another stab at enabling QEMU on systems with
> pathologically reduced IPA ranges such as the Apple M1 (previous
> version at [1]). Eventually, we're able to run a KVM guest with more
> than just 3GB of RAM on a system with a 36bit IPA space, and at most
> 123 vCPUs.
>
> This also addresses some pathological QEMU behaviours, where the
> highmem property is used as a flag allowing exposure of devices that
> can't possibly fit in the PA space of the VM, resulting in a guest
> failure.
>
> In the end, we generalise the notion of PA space when exposing
> individual devices in the expanded memory map, and treat highmem as
> another flavour of PA space restriction.



Applied to target-arm.next, thanks.

-- PMM