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| author | David Matlack <dmatlack@google.com> | 2022-01-19 23:07:37 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-02-10 13:50:43 -0500 |
| commit | cb00a70bd4b7e42dcbd6cd80b3f1697b10cdb44e (patch) | |
| tree | ed6bccba7f6a78e828a0aa55574193838a01aa2d /Documentation/admin-guide/kernel-parameters.txt | |
| parent | a3fe5dbda0a4bb7759dcd5a0ad713d347e020401 (diff) | |
| download | lwn-cb00a70bd4b7e42dcbd6cd80b3f1697b10cdb44e.tar.gz lwn-cb00a70bd4b7e42dcbd6cd80b3f1697b10cdb44e.zip | |
KVM: x86/mmu: Split huge pages mapped by the TDP MMU during KVM_CLEAR_DIRTY_LOG
When using KVM_DIRTY_LOG_INITIALLY_SET, huge pages are not
write-protected when dirty logging is enabled on the memslot. Instead
they are write-protected once userspace invokes KVM_CLEAR_DIRTY_LOG for
the first time and only for the specific sub-region being cleared.
Enhance KVM_CLEAR_DIRTY_LOG to also try to split huge pages prior to
write-protecting to avoid causing write-protection faults on vCPU
threads. This also allows userspace to smear the cost of huge page
splitting across multiple ioctls, rather than splitting the entire
memslot as is the case when initially-all-set is not used.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-17-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 5d80a0faa096..2a9746fe6c4a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2356,7 +2356,9 @@ KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If disabled, all huge pages in a memslot will be eagerly split when dirty logging is enabled on that memslot. If - enabled, huge pages will not be eagerly split. + enabled, eager page splitting will be performed during + the KVM_CLEAR_DIRTY ioctl, and only for the pages being + cleared. Eager page splitting currently only supports splitting huge pages mapped by the TDP MMU. |