diff options
| author |   Sean Christopherson <seanjc@google.com> | 2021-02-25 12:47:43 -0800 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2021-03-15 04:43:49 -0400 |
| commit | 5fc3424f8b854584f8f6fb6ea03f1419487fdc96 (patch) | |
| tree | ba8f20489b9d509ec107069e70e63d3664336605 /Documentation/virt/kvm/locking.rst | |
| parent | KVM: x86/mmu: Move logic for setting SPTE masks for EPT into the MMU proper (diff) | |
| download | linux-dev-5fc3424f8b854584f8f6fb6ea03f1419487fdc96.tar.xz linux-dev-5fc3424f8b854584f8f6fb6ea03f1419487fdc96.zip | |
KVM: x86/mmu: Make Host-writable and MMU-writable bit locations dynamic
Make the location of the HOST_WRITABLE and MMU_WRITABLE configurable for
a given KVM instance. This will allow EPT to use high available bits,
which in turn will free up bit 11 for a constant MMU_PRESENT bit.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt/kvm/locking.rst')
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index 85876afe0441..1fc860c007a3 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -44,18 +44,18 @@ following two cases: 2. Write-Protection: The SPTE is present and the fault is caused by write-protect. That means we just need to change the W bit of the spte. -What we use to avoid all the race is the SPTE_HOST_WRITEABLE bit and -SPTE_MMU_WRITEABLE bit on the spte: +What we use to avoid all the race is the Host-writable bit and MMU-writable bit +on the spte: -- SPTE_HOST_WRITEABLE means the gfn is writable on host. -- SPTE_MMU_WRITEABLE means the gfn is writable on mmu. The bit is set when - the gfn is writable on guest mmu and it is not write-protected by shadow - page write-protection. +- Host-writable means the gfn is writable in the host kernel page tables and in + its KVM memslot. +- MMU-writable means the gfn is writable in the guest's mmu and it is not + write-protected by shadow page write-protection. On fast page fault path, we will use cmpxchg to atomically set the spte W -bit if spte.SPTE_HOST_WRITEABLE = 1 and spte.SPTE_WRITE_PROTECT = 1, to -restore the saved R/X bits if for an access-traced spte, or both. This is -safe because whenever changing these bits can be detected by cmpxchg. +bit if spte.HOST_WRITEABLE = 1 and spte.WRITE_PROTECT = 1, to restore the saved +R/X bits if for an access-traced spte, or both. This is safe because whenever +changing these bits can be detected by cmpxchg. But we need carefully check these cases: |