mbox series

[v4,0/7] KVM: arm64: Hide unsupported MPAM from the guest

Message ID 20241004110714.2051604-1-joey.gouly@arm.com (mailing list archive)
Headers show
Series KVM: arm64: Hide unsupported MPAM from the guest | expand

Message

Joey Gouly Oct. 4, 2024, 11:07 a.m. UTC 
Hi,

I have taken over these patches from James, as he doesn't have the time to push
them forward currently.

James wrote:
	This series fixes up a long standing bug where MPAM was accidentally exposed
	to a guest, but the feature was not otherwise trapped or context switched.
	This could result in KVM warning about unexpected traps, and injecting an
	undef into the guest contradicting the ID registers.
	This would prevent an MPAM aware kernel from booting - fortunately, there
	aren't any of those.

	Ideally, we'd take the MPAM feature away from the ID registers, but that
	would leave existing guests unable to migrate to a newer kernel. Instead,
	just ignore that field when it matches the hardware. KVM wasn't going to
	expose MPAM anyway. The guest will not see MPAM in the id registers.

	This series includes the head.S and KVM changes to enable/disable traps. If
	MPAM is neither enabled nor emulated by EL3 firmware, these system register
	accesses will trap to EL3.
	If your kernel doesn't boot, and the problem bisects here - please update
	your firmware. MPAM has been supported by trusted firmware since v1.6 in
	2018. (also noted on patch 3).

changes since v3 [1]:
	- Converted to the new generated sysreg file
	- Added MPAM_frac support
	- Changed the Kconfig to hopefully make it obvious that it doesn't
	  actually enable MPAM for users
	- rebased onto v6.12-rc1

Thanks,
Joey

[1] https://lore.kernel.org/kvmarm/20240321165728.31907-1-james.morse@arm.com/

James Morse (7):
  arm64: head.S: Initialise MPAM EL2 registers and disable traps
  arm64/sysreg: Convert existing MPAM sysregs and add the remaining
    entries
  arm64: cpufeature: discover CPU support for MPAM
  KVM: arm64: Fix missing traps of guest accesses to the MPAM registers
  KVM: arm64: Add a macro for creating filtered sys_reg_descs entries
  KVM: arm64: Disable MPAM visibility by default and ignore VMM writes
  KVM: arm64: selftests: Test ID_AA64PFR0.MPAM isn't completely ignored

 .../arch/arm64/cpu-feature-registers.rst      |   2 +
 arch/arm64/Kconfig                            |  20 +++
 arch/arm64/include/asm/cpu.h                  |   1 +
 arch/arm64/include/asm/cpucaps.h              |   2 +
 arch/arm64/include/asm/cpufeature.h           |  12 ++
 arch/arm64/include/asm/el2_setup.h            |  16 ++
 arch/arm64/include/asm/kvm_arm.h              |   1 +
 arch/arm64/include/asm/mpam.h                 |  32 ++++
 arch/arm64/include/asm/sysreg.h               |  12 --
 arch/arm64/kernel/Makefile                    |   2 +
 arch/arm64/kernel/cpufeature.c                |  97 ++++++++++
 arch/arm64/kernel/cpuinfo.c                   |   4 +
 arch/arm64/kernel/image-vars.h                |   5 +
 arch/arm64/kernel/mpam.c                      |   8 +
 arch/arm64/kvm/hyp/include/hyp/switch.h       |  32 ++++
 arch/arm64/kvm/sys_regs.c                     | 114 +++++++++---
 arch/arm64/tools/cpucaps                      |   1 +
 arch/arm64/tools/sysreg                       | 166 ++++++++++++++++++
 .../selftests/kvm/aarch64/set_id_regs.c       | 100 ++++++++++-
 19 files changed, 587 insertions(+), 40 deletions(-)
 create mode 100644 arch/arm64/include/asm/mpam.h
 create mode 100644 arch/arm64/kernel/mpam.c