kernel/linux.git/virt/kvm/pfncache.c, branch v6.6

KVM: Skip unnecessary "unmap" if gpc is already valid during refresh

2022-11-30T19:25:24+00:00

When refreshing a gfn=>pfn cache, skip straight to unlocking if the cache already valid instead of stuffing the "old" variables to turn the unmapping outro into a nop. Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Drop @gpa from exported gfn=>pfn cache check() and refresh() helpers

2022-11-30T19:25:24+00:00

Drop the @gpa param from the exported check()+refresh() helpers and limit changing the cache's GPA to the activate path. All external users just feed in gpc->gpa, i.e. this is a fancy nop. Allowing users to change the GPA at check()+refresh() is dangerous as those helpers explicitly allow concurrent calls, e.g. KVM could get into a livelock scenario. It's also unclear as to what the expected behavior should be if multiple tasks attempt to refresh with different GPAs. Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Do not partially reinitialize gfn=>pfn cache during activation

2022-11-30T19:25:24+00:00

Don't partially reinitialize a gfn=>pfn cache when activating the cache, and instead assert that the cache is not valid during activation. Bug the VM if the assertion fails, as use-after-free and/or data corruption is all but guaranteed if KVM ends up with a valid-but-inactive cache. Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Drop KVM's API to allow temporarily unmapping gfn=>pfn cache

2022-11-30T19:25:24+00:00

Drop kvm_gpc_unmap() as it has no users and unclear requirements. The API was added as part of the original gfn_to_pfn_cache support, but its sole usage[*] was never merged. Fold the guts of kvm_gpc_unmap() into the deactivate path and drop the API. Omit acquiring refresh_lock as as concurrent calls to kvm_gpc_deactivate() are not allowed (this is not enforced, e.g. via lockdep. due to it being called during vCPU destruction). If/when temporary unmapping makes a comeback, the desirable behavior is likely to restrict temporary unmapping to vCPU-exclusive mappings and require the vcpu->mutex be held to serialize unmap. Use of the refresh_lock to protect unmapping was somewhat specuatively added by commit 93984f19e7bc ("KVM: Fully serialize gfn=>pfn cache refresh via mutex") to guard against concurrent unmaps, but the primary use case of the temporary unmap, nested virtualization[*], doesn't actually need or want concurrent unmaps. [*] https://lore.kernel.org/all/20211210163625.2886-7-dwmw2@infradead.org Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Use gfn_to_pfn_cache's immutable "kvm" in kvm_gpc_refresh()

2022-11-30T19:25:24+00:00

Make kvm_gpc_refresh() use kvm instance cached in gfn_to_pfn_cache. No functional change intended. Suggested-by: Sean Christopherson Signed-off-by: Michal Luczaj [sean: leave kvm_gpc_unmap() as-is] Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Clean up hva_to_pfn_retry()

2022-11-30T19:25:23+00:00

Make hva_to_pfn_retry() use kvm instance cached in gfn_to_pfn_cache. Suggested-by: Sean Christopherson Signed-off-by: Michal Luczaj Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Use gfn_to_pfn_cache's immutable "kvm" in kvm_gpc_check()

2022-11-30T19:25:23+00:00

Make kvm_gpc_check() use kvm instance cached in gfn_to_pfn_cache. Suggested-by: Sean Christopherson Signed-off-by: Michal Luczaj Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse

KVM: Store immutable gfn_to_pfn_cache properties

2022-11-30T19:25:23+00:00

Move the assignment of immutable properties @kvm, @vcpu, and @usage to the initializer. Make _activate() and _deactivate() use stored values. Note, @len is also effectively immutable for most cases, but not in the case of the Xen runstate cache, which may be split across two pages and the length of the first segment will depend on its address. Suggested-by: Sean Christopherson Signed-off-by: Michal Luczaj [sean: handle @len in a separate patch] Signed-off-by: Sean Christopherson [dwmw2: acknowledge that @len can actually change for some use cases] Signed-off-by: David Woodhouse

KVM: x86: Remove unused argument in gpc_unmap_khva()

2022-11-30T16:05:32+00:00

Remove the unused @kvm argument from gpc_unmap_khva(). Signed-off-by: Michal Luczaj Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse Signed-off-by: Paolo Bonzini

KVM: Shorten gfn_to_pfn_cache function names

2022-11-30T16:03:58+00:00

Formalize "gpc" as the acronym and use it in function names. No functional change intended. Suggested-by: Sean Christopherson Signed-off-by: Michal Luczaj Signed-off-by: Sean Christopherson Signed-off-by: David Woodhouse Signed-off-by: Paolo Bonzini