linux-kernel - [PATCH v4 0/4] KVM: x86: Dynamically allocate hashed page list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250523001138.3182794-1-seanjc@google.com>
Date: Thu, 22 May 2025 17:11:34 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Vipin Sharma <vipinsh@...gle.com>, James Houghton <jthoughton@...gle.com>
Subject: [PATCH v4 0/4] KVM: x86: Dynamically allocate hashed page list

Allocate the hashed list of shadow pages dynamically (separate from
struct kvm), and on-demand.  The hashed list is 32KiB, i.e. absolutely
belongs in a separate allocation, and is worth skipping if KVM isn't
shadowing guest PTEs for the VM.

I double checked that padding kvm_arch with a 4KiB array trips the assert,
but padding with 2KiB does not.  So knock on wood, I finally got the assert
right.  Maybe.

v4:
 - Use smp_store_release() and smp_load_acquire() instead of {READ,WRITE}_ONCE,
   and update the comments accordingly. [Paolo, James]
 - Move the kvm_tdx assert to tdx.c. [Paolo]
 - Fix the assertion, again.  [Vipin, in spirit if not in reality]
 - Add a patch to move TDX hardware setup to tdx.c.

v3:
 -  https://lore.kernel.org/all/20250516215422.2550669-1-seanjc@google.com
 - Add comments explaining the {READ,WRITE}_ONCE logic, and why it's safe
   to set the list outside of mmu_lock. [Vipin]
 - Make the assertions actually work. [Vipin]
 - Refine the assertions so they (hopefully) won't fail on kernels with
   a bunch of debug crud added.

v2:
 - https://lore.kernel.org/all/20250401155714.838398-1-seanjc@google.com
 - Actually defer allocation when using TDP MMU. [Vipin]
 - Free allocation on MMU teardown. [Vipin]

v1: https://lore.kernel.org/all/20250315024010.2360884-1-seanjc@google.com

Sean Christopherson (4):
  KVM: TDX: Move TDX hardware setup from main.c to tdx.c
  KVM: x86/mmu: Dynamically allocate shadow MMU's hashed page list
  KVM: x86: Use kvzalloc() to allocate VM struct
  KVM: x86/mmu: Defer allocation of shadow MMU's hashed page list

 arch/x86/include/asm/kvm_host.h |  6 +--
 arch/x86/kvm/mmu/mmu.c          | 75 ++++++++++++++++++++++++++++++---
 arch/x86/kvm/svm/svm.c          |  2 +
 arch/x86/kvm/vmx/main.c         | 36 +---------------
 arch/x86/kvm/vmx/tdx.c          | 47 +++++++++++++++------
 arch/x86/kvm/vmx/tdx.h          |  1 +
 arch/x86/kvm/vmx/vmx.c          |  2 +
 arch/x86/kvm/vmx/x86_ops.h      | 10 -----
 arch/x86/kvm/x86.c              |  5 ++-
 arch/x86/kvm/x86.h              | 22 ++++++++++
 10 files changed, 139 insertions(+), 67 deletions(-)


base-commit: 3f7b307757ecffc1c18ede9ee3cf9ce8101f3cc9
-- 
2.49.0.1151.ga128411c76-goog