From patchwork Wed Feb 5 18:23:49 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13961702 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5927913D897 for ; Wed, 5 Feb 2025 18:24:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738779864; cv=none; b=lZtLnxLdylt/tqXLaInui4u2XWeLdIzRRJvjkIzZXFzbqZuBolHYf+zYodeCjFAeMW3+hAFKpZZ9y/zVQLN68uxSDo3ZK8cpmLs5hVFL944sjD05zZdiWg7nsu4DITpOXfvrcxKcGwfolZ2f1kxKrXFBC83SsaduG8BpSjsMKwM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738779864; c=relaxed/simple; bh=h5JP2BryQ6La04KRJax72/zZCxD3zb5ksq6AY2dGX7k=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pjwPLM/47EwixqqQnrtzv2oUUM7Ihgs4a2xbAy/dmHSI412zw/YC6I2MYdMzIjWbUg5Alpw0cvN6QgXZh7SSpxj/pmfn95rnZVPrLA6NCH6hDb7LWCp64LTDdHwmoQhe52h8KkOgu3yzMpJFhGZ5QaCZ7K3GBkyvpJp7kHx3AcA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=SlqaUgxX; arc=none smtp.client-ip=91.218.175.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="SlqaUgxX" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1738779852; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=SSaQQ6ZsNVEwjPV5fpi9CdPM1gUz5qsUb8Uq5Q1XNrY=; b=SlqaUgxXoAL9gJLcKrcRhl2JvoBczbpIE+nvI5SHZIZ3AAAPC+G945I9w4lgn4J8qOPzM4 FqSE2HNZKSJgXMG2t/qN35rjqeRFsCpugDICQCDs+m+R7dmEnZMFB98Y3ieskR5hkYwmfg IdS+kHAz6vIBGyXmMAXCgQ5sfY+v51A= From: Yosry Ahmed To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 00/13] Optimize nSVM TLB flushes Date: Wed, 5 Feb 2025 18:23:49 +0000 Message-ID: <20250205182402.2147495-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT Currently KVM does a TLB flush and an MMU sync on every nested transition (L1 <-> L2), because it uses the same ASID to run both L1 and L2. This series addresses that by giving a separate ASID to L2, adding the necessary TLB management for it, and properly virtualizing TLB flushes for L1. Patch 1 introduces a separate ASID for L2, althoug not properly handled yet, so it keeps the unconditional flushes. Patches 2 to 6 are some refactoring and groundwork. Patches 7 to 12 add the actual TLB management for nSVM, some of which are items on the TODO list in nested_svm_transition_tlb_flush(). Patch 13 finally stops the unconditional flushes on every nested transition. I tested this by booting an L2 and running some basic workloads, including a CPUID microbenchmark to measure the performance improvement (numbers in the last patch). I sent the RFC to get feedback on the general approach, and meanwhile I will try to run more tests that could exercise TLB flushing. Yosry Ahmed (13): KVM: nSVM: Track the ASID per-VMCB KVM: nSVM: Rework svm_flush_tlb_asid() to operate on a given VMCB KVM: nSVM: Split nested_svm_transition_tlb_flush() into entry/exit fns KVM: SVM: Introduce helpers for updating TLB_CONTROL KVM: x86/mmu: rename __kvm_mmu_invalidate_addr() KVM: x86/mmu: Allow skipping the gva flush in kvm_mmu_invalidate_addr() KVM: nSVM: Handle INVLPGA interception correctly KVM: nSVM: Flush both L1 and L2 ASIDs on KVM_REQ_TLB_FLUSH KVM: nSVM: Handle nested TLB flush requests through TLB_CONTROL KVM: nSVM: Flush the TLB if L1 changes L2's ASID KVM: nSVM: Do not reset TLB_CONTROL in VMCB02 on nested entry KVM: nSVM: Service local TLB flushes before nested transitions KVM: nSVM: Stop bombing the TLB on nested transitions arch/x86/include/asm/kvm_host.h | 2 + arch/x86/include/asm/svm.h | 6 --- arch/x86/kvm/mmu/mmu.c | 22 +++++--- arch/x86/kvm/svm/nested.c | 64 +++++++++++++++------- arch/x86/kvm/svm/sev.c | 4 +- arch/x86/kvm/svm/svm.c | 95 ++++++++++++++++++++++++++------- arch/x86/kvm/svm/svm.h | 33 +++++++++++- 7 files changed, 170 insertions(+), 56 deletions(-)