From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2257E43304E; Tue, 28 Jul 2026 17:42:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785260560; cv=none; b=gxoJz5J6oN8mBFZgcX21sOrSxy4rPeUQOyFRWs20qpsTU6UqNPrzM27OkDq7RdkYJjH3wbzTX9KrZ3o2YP9DXgi1IX3ML+1PrfzGJBfvlpTp0rsKmDi7/DE0vZitHs7z/KQNO1i7pTagOJh9ZuF1WGklv+H5JC5ohrwITjDT1Xk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785260560; c=relaxed/simple; bh=DIRwx8Rd+0JQucKNw0YrOB92qISp+eIVXT2TFkYw9lE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=r377OherY0WE57iwpUUV2j6fOBG5ttPlabn2yjFLtkporwVTJvH5xLkQIHHNXH7kKmdzFoI3fajEs9dDs8XWs2z9F/Sj2C534d7fKAFTEqd6rZxsdo+T2xeg6yYv2syl2iq/yk+NIbmn6WcOMJvR9tGPN1MX2oNmL2ksbwFf0gA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZEbooDmX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZEbooDmX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFBD51F000E9; Tue, 28 Jul 2026 17:42:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785260559; bh=c7NHq/TB28l3PhrkT5P2W1yi5Z28aU/T3OvU/1OdU/s=; h=From:To:Cc:Subject:Date; b=ZEbooDmXn0aSnEmohldRUZoGs2M4fGoWqVJ7UDXYuEvAhPo8DEgg8IF9sYXSZ5geZ 7JVwJZ0u7OCT5lQj9ekxkPJEP1Dw7iqGvobpr5kqAw2QAraotB/g4A4OOl0wzKvQaP FJHvvCyzhis99Age7FYzPyjdZFuwan11ksQ8dtXTXSC1dqMrWAfYHNgiUEZ92tydB8 SthyJYZRo4PgeXIo6iEvD1fSI9jLXDSkAv5fYwIAz86DAW8ilTMuxdblVlulsAltyC owpBXTZzCMl1yyRIPiCdOtqSmMydXHi7dok0LiaFyqSqfqPIn+oikeVFL7xD6/XlVg WNU72IbH1Ayrw== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v5 00/13] KVM: selftests: Stress save+restore and #PF (ft. nested) Date: Tue, 28 Jul 2026 17:42:19 +0000 Message-ID: <20260728174232.2423257-1-yosry@kernel.org> X-Mailer: git-send-email 2.55.0.487.gaf234c4eb3-goog Precedence: bulk X-Mailing-List: kvm@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 commit 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 (1-6) are prep patches, fixing GPR and RFLAGS switching for nSVM and generalizing GPR switching to cover nVMX, which is needed for the test to run properly with nVMX. Patch 6 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 (7-9) add minor infrastructure improvements (assertion failure formatting and exposing MMU masks to the guest). Patches (10-13) 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, nested support, and triggering L2->L1 exits. After the last patch, the test reliably reproduces the CR2 bug. v4 -> v5: - Only set KVM_CAP_EXCEPTION_PAYLOAD when running nested [Sashiko]. - Do not intercept #PF by default for nVMX tests [Sean]. - Nits and cleanups [Sean]. v3 -> v4: - Switch guest_regs back to a struct and provide struct offsets as ASM constraints similar to kvm-unit-tests [Sean]. - Expose PTE masks to guests as part of a guest MMU [Sean]. - Use __stringify() from instead of custom STR() and XSTR() macros [Sean]. - Handle guest RFLAGS save/restore as part of guest_regs. - Run both L0 and L2 tests sequentially by default if nested is supported, instead of requiring a '-n' command line argument [Sean]. - Minor fixups and cleanups [Sean]. v2 -> v3: - Rebased on top of L2 stack rework in selftests. - Fix GPR array size (i.e. NR_GUEST_REGS) [Sashiko]. - Handle evmcs_vmlaunch() and evmcs_vmresume() [Sashiko]. - Fix off-by-one assertion error in intermediate patches. - Increase inter-signal delay from 100us to 1msec. v1 -> v2: - Switch guest_regs to an array, which simplifies the offsets calculation and forgoes the dependency on using OFFSET() or defining the struct offsets for assembly otherwise. - Move page table mapping to the test (instead of a generic helper), as the helper mistakenly tried to map the entire memslot, not just page tables. - Do not use identity mappings for page tables as it collisions with GVAs used for ELF in some cases. - Simplify page table walking by using loops. - Make sure the signals are ignored before creating the signaling thread [Sashiko] - Assert that the guest actually ran and had page faults [Sashiko] - Add a patch to fix RAX and RFLAGS offsets in run_guest() [Sashiko] - Initialize exception_has_payload when injecting a #UD [Sashiko] - Only check KVM_STATE_NESTED_GUEST_MODE when running in nested mode [Sashiko] v1: https://lore.kernel.org/all/20260518202514.2037078-1-yosry@kernel.org/ v2: https://lore.kernel.org/kvm/20260604203546.365658-1-yosry@kernel.org/ v3: https://lore.kernel.org/kvm/20260629183746.699840-1-yosry@kernel.org/ v4: https://lore.kernel.org/kvm/20260727235228.1007324-1-yosry@kernel.org/ Yosry Ahmed (13): KVM: selftests: Use __stringify() instead of custom XSTR() macros KVM: selftests: Fix RAX and RFLAGS VMCB offsets when running L2 KVM: selftests: Rework GPR registers switching for SVM (and fix offsets) KVM: selftests: Handle rflags save/restore for SVM in guest_regs KVM: selftests: Reuse GPR switching logic for nVMX KVM: selftests: Drop HORRIFIC_L2_UCALL_CLOBBER_HACK KVM: selftests: Add a blank line before logging assertion failures KVM: selftests: Expose PTE masks to guests as part of an MMU KVM: selftests: Do not intercept #PF by default in nVMX tests 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 + .../testing/selftests/kvm/include/test_util.h | 1 + .../testing/selftests/kvm/include/x86/evmcs.h | 46 +-- .../selftests/kvm/include/x86/processor.h | 52 +++- tools/testing/selftests/kvm/include/x86/vmx.h | 69 ++--- tools/testing/selftests/kvm/lib/assert.c | 2 +- .../testing/selftests/kvm/lib/x86/processor.c | 14 + tools/testing/selftests/kvm/lib/x86/svm.c | 62 ++-- tools/testing/selftests/kvm/lib/x86/ucall.c | 32 +- tools/testing/selftests/kvm/lib/x86/vmx.c | 2 +- .../kvm/x86/evmcs_smm_controls_test.c | 5 +- .../selftests/kvm/x86/fix_hypercall_test.c | 1 - .../kvm/x86/save_restore_pf_stress_test.c | 288 ++++++++++++++++++ tools/testing/selftests/kvm/x86/smm_test.c | 5 +- 14 files changed, 439 insertions(+), 141 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86/save_restore_pf_stress_test.c base-commit: 271255273d5ff348fe29d89fe4712b2f7f7907c3 -- 2.55.0.487.gaf234c4eb3-goog