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KVM: Documentation: Add the missing description for mmu_valid_gen into kvm_mmu_page

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Add the description for mmu_valid_gen into kvm_mmu_page description.
mmu_valid_gen is used in shadow MMU for fast zapping. Update the doc to
reflect that.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-6-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Mingwei Zhang 2023-09-12 18:45:52 +00:00 committed by Sean Christopherson
parent 6a713928ae
commit c3204c406b
1 changed files with 10 additions and 0 deletions
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10
Documentation/virt/kvm/x86/mmu.rst
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@ -208,6 +208,16 @@ Shadow pages contain the following information:
The page is not backed by a guest page table, but its first entry
points to one. This is set if NPT uses 5-level page tables (host
CR4.LA57=1) and is shadowing L1's 4-level NPT (L1 CR4.LA57=0).
mmu_valid_gen:
The MMU generation of this page, used to fast zap of all MMU pages within a
VM without blocking vCPUs too long. Specifically, KVM updates the per-VM
valid MMU generation which causes the mismatch of mmu_valid_gen for each mmu
page. This makes all existing MMU pages obsolete. Obsolete pages can't be
used. Therefore, vCPUs must load a new, valid root before re-entering the
guest. The MMU generation is only ever '0' or '1'. Note, the TDP MMU doesn't
use this field as non-root TDP MMU pages are reachable only from their
owning root. Thus it suffices for TDP MMU to use role.invalid in root pages
to invalidate all MMU pages.
gfn:
Either the guest page table containing the translations shadowed by this
page, or the base page frame for linear translations. See role.direct.