KVM: arm64: Expose new KVM cap for cacheable PFNMAP

Introduce a new KVM capability to expose to the userspace whether
cacheable mapping of PFNMAP is supported.

The ability to safely do the cacheable mapping of PFNMAP is contingent
on S2FWB and ARM64_HAS_CACHE_DIC. S2FWB allows KVM to avoid flushing
the D cache, ARM64_HAS_CACHE_DIC allows KVM to avoid flushing the icache
and turns icache_inval_pou() into a NOP. The cap would be false if
those requirements are missing and is checked by making use of
kvm_arch_supports_cacheable_pfnmap.

This capability would allow userspace to discover the support.
It could for instance be used by userspace to prevent live-migration
across FWB and non-FWB hosts.

CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Jason Gunthorpe <jgg@nvidia.com>
CC: Oliver Upton <oliver.upton@linux.dev>
CC: David Hildenbrand <david@redhat.com>
Suggested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20250705071717.5062-7-ankita@nvidia.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

This commit is contained in:

Ankit Agrawal

2025-07-07 16:54:52 -07:00

committed by

Oliver Upton

parent 0c67288e0c

commit f55ce5a6cd

3 changed files with 20 additions and 1 deletions

									
										include/uapi/linux/kvm.h
									
		+1
		
												View File
												
				@@ -956,6 +956,7 @@ struct kvm_enable_cap {

				#define KVM_CAP_ARM_EL2 240

				#define KVM_CAP_ARM_EL2_E2H0 241

				#define KVM_CAP_RISCV_MP_STATE_RESET 242

				#define KVM_CAP_ARM_CACHEABLE_PFNMAP_SUPPORTED 243

				struct kvm_irq_routing_irqchip {

					__u32 irqchip;