linux-kernel - [PATCH 0/7] x86, KVM: Optimize SEV cache flushing

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Message-ID: <20250227014858.3244505-1-seanjc@google.com>
Date: Wed, 26 Feb 2025 17:48:51 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Zheyun Shen <szy0127@...u.edu.cn>, Tom Lendacky <thomas.lendacky@....com>, 
	Kevin Loughlin <kevinloughlin@...gle.com>, Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH 0/7] x86, KVM: Optimize SEV cache flushing

This is the combination of Kevin's WBNOINVD series[1] with Zheyun's targeted
flushing series[2].  This is very, very lightly tested (emphasis on "very").

Note, I dropped Reviewed-by tags for patches to which I made non-trivial
modifications.

[1] https://lore.kernel.org/all/20250201000259.3289143-1-kevinloughlin@google.com
[2] https://lore.kernel.org/all/20250128015345.7929-1-szy0127@sjtu.edu.cn

Relative to those series:

 - Name the WBNOINVD opcode macro ASM_WBNOINVD to avoid a conflict with
   KVM's CPUID stuff.
 - Fix issues with SMP=n.
 - Define all helpers in x86/lib.
 - Don't return 0 from the helpers.
 - Rename the CPU bitmap to avoid a naming collisions with KVM's existing
   pCPU bitmap for WBINVD, and to not have WBINVD (versus WBNOINVD) in the
   name.
 - Fix builds where CPU bitmaps are off-stack.
 - Massage comments.
 - Mark a CPU as having done VMRUN in pre_sev_run(), but test to see if
   the CPU already ran to avoid the locked RMW, i.e. to (hopefully) avoid
   bouncing the cache line.

Kevin Loughlin (2):
  x86, lib: Add WBNOINVD helper functions
  KVM: SEV: Prefer WBNOINVD over WBINVD for cache maintenance efficiency

Sean Christopherson (2):
  x86, lib: Drop the unused return value from wbinvd_on_all_cpus()
  KVM: x86: Use wbinvd_on_cpu() instead of an open-coded equivalent

Zheyun Shen (3):
  KVM: SVM: Remove wbinvd in sev_vm_destroy()
  x86, lib: Add wbinvd and wbnoinvd helpers to target multiple CPUs
  KVM: SVM: Flush cache only on CPUs running SEV guest

 arch/x86/include/asm/smp.h           | 23 ++++++--
 arch/x86/include/asm/special_insns.h | 19 ++++++-
 arch/x86/kvm/svm/sev.c               | 79 +++++++++++++++++++---------
 arch/x86/kvm/svm/svm.h               |  1 +
 arch/x86/kvm/x86.c                   | 11 +---
 arch/x86/lib/cache-smp.c             | 26 ++++++++-
 6 files changed, 119 insertions(+), 40 deletions(-)


base-commit: fed48e2967f402f561d80075a20c5c9e16866e53
-- 
2.48.1.711.g2feabab25a-goog