From: Paul Durrant <pdurrant@xxxxxxxxxx>
Currently we treat the shared_info page as guest memory and the VMM informs
KVM of its location using a GFN. However it is not guest memory as such;
it's an overlay page. So we pointlessly invalidate and re-cache a mapping
to the *same page* of memory every time the guest requests that shared_info
be mapped into its address space. Let's avoid doing that by modifying the
pfncache code to allow activation using a fixed userspace HVA as well as
a GPA.
Also, if the guest does not hypercall to explicitly set a pointer to a
vcpu_info in its own memory, the default vcpu_info embedded in the
shared_info page should be used. At the moment the VMM has to set up a
pointer to the structure explicitly (again treating it like it's in
guest memory, despite being in an overlay page). Let's also avoid the
need for that. We already have a cached mapping for the shared_info
page so just use that directly by default.
Paul Durrant (8):
KVM: pfncache: add a map helper function
KVM: pfncache: add a mark-dirty helper
KVM: pfncache: add a helper to get the gpa
KVM: pfncache: base offset check on khva rather than gpa
KVM: pfncache: allow a cache to be activated with a fixed (userspace)
HVA
KVM: xen: allow shared_info to be mapped by fixed HVA
KVM: xen: prepare for using 'default' vcpu_info
KVM: xen: automatically use the vcpu_info embedded in shared_info
arch/x86/include/asm/kvm_host.h | 4 +
arch/x86/kvm/x86.c | 18 ++---
arch/x86/kvm/xen.c | 121 ++++++++++++++++++++++--------
arch/x86/kvm/xen.h | 6 +-
include/linux/kvm_host.h | 43 +++++++++++
include/linux/kvm_types.h | 3 +-
include/uapi/linux/kvm.h | 7 +-
virt/kvm/pfncache.c | 129 +++++++++++++++++++++++---------
8 files changed, 251 insertions(+), 80 deletions(-)
---
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
--
2.39.2
