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 (13):
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: prevent vcpu_id from changing whilst shared_info is valid
KVM: xen: automatically use the vcpu_info embedded in shared_info
KVM: selftests / xen: set KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID
KVM: selftests / xen: map shared_info using HVA rather than GFN
KVM: selftests / xen: don't explicitly set the vcpu_info address
KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability
Documentation/virt/kvm/api.rst | 49 ++++--
arch/x86/include/asm/kvm_host.h | 4 +
arch/x86/kvm/x86.c | 17 +--
arch/x86/kvm/xen.c | 139 +++++++++++++-----
arch/x86/kvm/xen.h | 6 +-
include/linux/kvm_host.h | 43 ++++++
include/linux/kvm_types.h | 3 +-
include/uapi/linux/kvm.h | 6 +-
.../selftests/kvm/x86_64/xen_shinfo_test.c | 75 ++++++++--
virt/kvm/pfncache.c | 129 +++++++++++-----
10 files changed, 360 insertions(+), 111 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
