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Date: Sun, 6 Jul 2025 20:02:35 -0500
From: Catalin Marinas <catalin.marinas@arm.com>
To: ankita@nvidia.com
Cc: jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev,
	joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com,
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Subject: Re: [PATCH v10 6/6] KVM: arm64: Expose new KVM cap for cacheable
 PFNMAP
Message-ID: <aGscq_R69UpMXpGX@arm.com>
References: <20250705071717.5062-1-ankita@nvidia.com>
 <20250705071717.5062-7-ankita@nvidia.com>
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In-Reply-To: <20250705071717.5062-7-ankita@nvidia.com>

On Sat, Jul 05, 2025 at 07:17:17AM +0000, ankita@nvidia.com wrote:
> From: Ankit Agrawal <ankita@nvidia.com>
> 
> 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>