From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 53113392C2C; Mon, 18 May 2026 20:25:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779135924; cv=none; b=u7B9zBZIIgYZYQCfCjw16tTOcuHqkyIqEUl37K8QSHE8gSyooaJEfWVYGkVE+RUkRMI6XtCoXibt6LLk461t2HJf7Uia04rjT5uf8thgndyWHT5wDe23MtOyjr/BUdAY44+ZnvRpsny/1LV5E7OE4Qz2kRj0hhU8NxDR1ls5s8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779135924; c=relaxed/simple; bh=vzbbtmO5nMWBWyq8FbcXn7UnT0/b84Bgk2wFekjS614=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=WJkJ6g63O2o62oF4+nBsVpoKBIXfYnArfntNR8SsrWKTcd0dO88vhXoJNjNAvs/qv2NURvod4+2Z96e+Oe4NdkyxoRwC2MOmPu4eCze9NEAacw1ceJCIeFoH0RBhDY5HXYsnShhWMKRbz/jk3wdQFeZg2ag70C5++ZXosr+PX0A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gt89QBc2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gt89QBc2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAB88C2BCB7; Mon, 18 May 2026 20:25:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779135923; bh=vzbbtmO5nMWBWyq8FbcXn7UnT0/b84Bgk2wFekjS614=; h=From:To:Cc:Subject:Date:From; b=gt89QBc2T5Hl8gCGKjsLEIMg7536/fk0S3m0BfpuK83ZX94KV+NR/bbGJ4AvHC4Xv ZNOuYmjWrZ3cL07x5OmOlso2fFwOGN88u8/VdfRiMgiQPndGvnEIe1VKVXoqi7sRdi 3SW9B4D7SvZBlhzNjguezy4NYZBrvrmTWscMuKWihcFlgqTeGUMfP+8FPpwW+RxaCR 9Vet9o4mqAOymV1+T80qnaDtwN23Gm/Sst8TbyD4ra3Af2oWNDljw4PtudUD59z7H/ Tmx9NdhyW337sij0LStmbfe9ltWCl+FK+e1Yg36RjXk3pf2Nw4zbY/qVMQaQiNTlIX 2mTAtk+jvxbaA== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH 0/8] KVM: selftests: Stress save+restore and #PF (ft. nested) Date: Mon, 18 May 2026 20:25:06 +0000 Message-ID: <20260518202514.2037078-1-yosry@kernel.org> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a stress test for save+restore while the guest is triggering and handling #PFs, in both L1 and L2. The goal was to create a generic selftest that would catch bugs like the one fixed by 5c247d08bc81 ("KVM: nSVM: Use vcpu->arch.cr2 when updating vmcb12 on nested #VMEXIT"), instead of relying on high-level testing (e.g. building GCC in L2) to catch it. The test tries to be as generic as possible by triggering #PFs in a guest and installing a proper #PF handler, while the host is continuously doing save+restore cycles. Exiting to userspace is randomly triggered by a second thread that constantly signals the vCPU thread. Patches (1-4) are prep patches, fixing GPR switching for nSVM and generalizing it to cover nVMX, which is needed for the test to run properly with nVMX. Patch 4 removes HORRIFIC_L2_UCALL_CLOBBER_HACK, as it is no longer needed. While this series does not have the "complete" fix added by commit 6783ca4105a7 ("KVM: selftests: Add a shameful hack to preserve/clobber GPRs across ucall"), it's a good step in the right direction. Patches (5-8) add the actual test. The test is first introduced as a simple (read: dummy) stress test that just explicitly syncs to userspace after each #PF handling to do save+restore, then gradually evolves to add the random signaling and nested support. After the last patch, the test reliably reproduces the CR2 bug. This series conflicts with reworking L2 stack allocation in [1], but the conflict should be trivial to fix regardless of which series lands first. [1]https://lore.kernel.org/kvm/20260506015733.1671124-1-yosry@kernel.org/ Yosry Ahmed (8): KVM: selftests: Fix offsets in GPR switching for nSVM KVM: selftests: Move GPR load/save definitions outside of nSVM code KVM: selftests: Reuse GPR switching logic for nVMX KVM: selftests: Drop HORRIFIC_L2_UCALL_CLOBBER_HACK KVM: selftests: Add basic stress test for save+restore and #PF handling KVM: selftests: Trigger save+restore randomly in the #PF stress test KVM: selftests: Support running stress save+restore and #PF test in L2 KVM: selftests: Trigger L2->L1 exits stress save+restore and #PF test tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/include/x86/processor.h | 65 +++- tools/testing/selftests/kvm/include/x86/vmx.h | 46 +-- .../testing/selftests/kvm/lib/x86/processor.c | 13 + tools/testing/selftests/kvm/lib/x86/svm.c | 29 +- tools/testing/selftests/kvm/lib/x86/ucall.c | 32 +- .../kvm/x86/stress_save_restore_pf_test.c | 320 ++++++++++++++++++ 7 files changed, 414 insertions(+), 92 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86/stress_save_restore_pf_test.c base-commit: a9512a611bd030088f13477258d1f8103cceaa40 -- 2.54.0.563.g4f69b47b94-goog