The patch titled
KVM: Workaround cr0.cd (cache disable) bit leak from guest to host
has been added to the -mm tree. Its filename is
kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: KVM: Workaround cr0.cd (cache disable) bit leak from guest to host
From: Avi Kivity <avi@xxxxxxxxxxxx>
On Core-not-2 processors (or on laptops - not sure what the cause is), the
cache disable bit sometimes leaks from the guest cr0 to the host cr0. This
leaves the host limping along at a snail's pace long after the guest has left.
This might be a bug in the processor or in the smm (system management mode)
bios.
Workaround by giving the guest a virtual cr0.cd (and also cr0.nw for good
measure) and keeping the real bits always clear.
This makes sense even without the bug: the processor cache is a host resource,
not a guest resource, and the guest has no business disabling it.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/kvm/kvm.h | 4 +++-
drivers/kvm/kvm_main.c | 6 ++++--
2 files changed, 7 insertions(+), 3 deletions(-)
diff -puN drivers/kvm/kvm.h~kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to drivers/kvm/kvm.h
--- a/drivers/kvm/kvm.h~kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to
+++ a/drivers/kvm/kvm.h
@@ -31,8 +31,10 @@
#define CR4_VMXE_MASK (1ULL << 13)
#define KVM_GUEST_CR0_MASK \
+ (CR0_PG_MASK | CR0_PE_MASK | CR0_WP_MASK | CR0_NE_MASK \
+ | CR0_NW_MASK | CR0_CD_MASK)
+#define KVM_VM_CR0_ALWAYS_ON \
(CR0_PG_MASK | CR0_PE_MASK | CR0_WP_MASK | CR0_NE_MASK)
-#define KVM_VM_CR0_ALWAYS_ON KVM_GUEST_CR0_MASK
#define KVM_GUEST_CR4_MASK \
(CR4_PSE_MASK | CR4_PAE_MASK | CR4_PGE_MASK | CR4_VMXE_MASK | CR4_VME_MASK)
diff -puN drivers/kvm/kvm_main.c~kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to drivers/kvm/kvm_main.c
--- a/drivers/kvm/kvm_main.c~kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to
+++ a/drivers/kvm/kvm_main.c
@@ -871,7 +871,8 @@ static void __set_cr0(struct kvm_vcpu *v
#endif
vmcs_writel(CR0_READ_SHADOW, cr0);
- vmcs_writel(GUEST_CR0, cr0 | KVM_VM_CR0_ALWAYS_ON);
+ vmcs_writel(GUEST_CR0,
+ (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON);
}
static int pdptrs_have_reserved_bits_set(struct kvm_vcpu *vcpu,
@@ -1955,7 +1956,8 @@ static int kvm_dev_ioctl_set_sregs(struc
vcpu->rmode.active = ((sregs->cr0 & CR0_PE_MASK) == 0);
update_exception_bitmap(vcpu);
vmcs_writel(CR0_READ_SHADOW, sregs->cr0);
- vmcs_writel(GUEST_CR0, sregs->cr0 | KVM_VM_CR0_ALWAYS_ON);
+ vmcs_writel(GUEST_CR0,
+ (sregs->cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON);
mmu_reset_needed |= guest_cr4() != sregs->cr4;
__set_cr4(vcpu, sregs->cr4);
_
Patches currently in -mm which might be from avi@xxxxxxxxxxxx are
kvm-userspace-interface.patch
kvm-intel-virtual-mode-extensions-definitions.patch
kvm-kvm-data-structures.patch
kvm-random-accessors-and-constants.patch
kvm-virtualization-infrastructure.patch
kvm-memory-slot-management.patch
kvm-vcpu-creation-and-maintenance.patch
kvm-workaround-cr0cd-cache-disable-bit-leak-from-guest-to.patch
kvm-vcpu-execution-loop.patch
kvm-define-exit-handlers.patch
kvm-less-common-exit-handlers.patch
kvm-mmu.patch
kvm-x86-emulator.patch
kvm-plumbing.patch
kvm-dynamically-determine-which-msrs-to-load-and-save.patch
kvm-fix-calculation-of-initial-value-of-rdx-register.patch
kvm-fix-guest-cr4-corruption.patch
-
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