[RFC PATCH v3 0/3] x86/hvm: Introduce Xen-wide ASID allocator

["Teddy Astie" <teddy.astie@vates.tech>]

From: Vaishali Thakkar <vaishali.thakkar@suse.com> (formely vates.tech)
original v2: https://lore.kernel.org/xen-devel/cover.1723574652.git.vaishali.thakkar@vates.tech/

This is part of the effort to enable AMD SEV technologies in Xen. For
AMD SEV support, we need a fixed ASID associated with all vcpus of the
same domain throughout the domain's lifetime. This is because for SEV/
SEV-{ES,SNP} VM, the ASID is the index which is associated with the
encryption key.

Currently, ASID generation and management is done per-PCPU in Xen. And
at the time of each VMENTER, the ASID associated with vcpus of the
domain is changed. This implementation is incompatible with SEV
technologies for the above mentioned reasons. In a discussion with
Andrew Cooper, it came up that it'll be nice to have fixed ASIDs not
only for SEV VMs but also for all VMs. Because it opens up the
opportunity to use features like TLBSYNC/INVLPGB (Section
5.5.3 in AMD Architecture manual[0]) and Intel RAR [1] for broadcasting
the TLB Invalidations.

Changes since v2:
-----------------
A lot has changed since v2, though the concept is still the same.
The asid management logic is a lot simpler, by relying a bitmap to track
all used ASIDs, and freeing them individually instead of using a ASID
reclaim strategy.

When a vCPU needs to be flushed, it is signaled through vcpu.needs_tlb_flush,
indicating that the next time the guest is re-entered, a TLB flush will have
to be issued (either using per-context invvpid on Intel or flush-by-asid
tlb_control on AMD).

Changes were tested on Intel Haswell, KVM AMD virtual machine and AMD EPYC Genoa.

Teddy Astie (3):
  vmx: Rewrite vpid_sync_vcpu_gva
  vmx: Introduce vcpu single context VPID invalidation
  x86/hvm: Introduce Xen-wide ASID allocator

 xen/arch/x86/flushtlb.c                |  31 +++---
 xen/arch/x86/hvm/asid.c                | 148 +++++++++----------------
 xen/arch/x86/hvm/emulate.c             |   2 +-
 xen/arch/x86/hvm/hvm.c                 |  14 ++-
 xen/arch/x86/hvm/nestedhvm.c           |   6 +-
 xen/arch/x86/hvm/svm/asid.c            |  77 ++++++++-----
 xen/arch/x86/hvm/svm/nestedsvm.c       |   1 -
 xen/arch/x86/hvm/svm/svm.c             |  36 +++---
 xen/arch/x86/hvm/svm/svm.h             |   4 -
 xen/arch/x86/hvm/vmx/vmcs.c            |   5 +-
 xen/arch/x86/hvm/vmx/vmx.c             |  68 ++++++------
 xen/arch/x86/hvm/vmx/vvmx.c            |   5 +-
 xen/arch/x86/include/asm/flushtlb.h    |   7 --
 xen/arch/x86/include/asm/hvm/asid.h    |  25 ++---
 xen/arch/x86/include/asm/hvm/domain.h  |   1 +
 xen/arch/x86/include/asm/hvm/hvm.h     |  15 +--
 xen/arch/x86/include/asm/hvm/svm/svm.h |   5 +
 xen/arch/x86/include/asm/hvm/vcpu.h    |  10 +-
 xen/arch/x86/include/asm/hvm/vmx/vmx.h |  44 ++++----
 xen/arch/x86/mm/hap/hap.c              |   6 +-
 xen/arch/x86/mm/p2m.c                  |   7 +-
 xen/arch/x86/mm/paging.c               |   2 +-
 xen/arch/x86/mm/shadow/hvm.c           |   1 +
 xen/arch/x86/mm/shadow/multi.c         |  12 +-
 xen/include/xen/sched.h                |   2 +
 25 files changed, 249 insertions(+), 285 deletions(-)

-- 
2.50.0



Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech