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 D908A397E73; Mon, 29 Jun 2026 18:37:59 +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=1782758281; cv=none; b=RHxtm9BGHe7LlTWXVnrfz+jJl5jCIWGT3NdknE1cGSyX8C4vx9cMe3EpOtxbkveMXewVBnhlw+CRITJK6k+TQOKycbBud77siWuEJESULQMjXe7rec7gGe5KNZEqmDTCovWKmxgUx3wP5S8wfssPzZ+GRkwAkr+jnytAQsG28iQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782758281; c=relaxed/simple; bh=3AKK36BaWkeorLzWOpN5Tvibn3HevnVbwavTna18koY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=s1clHMokxoyRzWM930tlhY6KF5J7Dlg1HGRUWoQda9KgM3qV8clbX1jduPxjbM39+R+5UgDtG3jy5P0eqBEXEtbDrZ0+LC4yWbkHxqD4hbf19vfsaFz4n9f8oPk5uKm6Ru63VsKVwa5O0gm5tKznxxQ03t7PJBZQbphwwzzTfYY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HZ6l55K5; 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="HZ6l55K5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 421371F000E9; Mon, 29 Jun 2026 18:37:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782758279; bh=64OyJFZjyxk17y8fQvtUvOfVXfFmYipSgoTrYIU7HjY=; h=From:To:Cc:Subject:Date; b=HZ6l55K5LBmii7Ks32O0LyuDAv2g/M9lpzsDeqgLeqAUufB32BJDpLHGgZjsPXO5V 7lge2qCKV3hJO0ga8yVKvCr5gWHDPYeEamfxbwTrW2Kp+CAZ7PcBFFcL2LMzUvK68G bPmIF9fb9pZeoBDO6miUlHxmNK677lvjwZEYxMkq9A52FM8wnK1EIw8622OaWkRXr9 8o7IxIv0nV9oM7s/mI2KiVQQ5SsLinKFhumlRkz6WP3/Y8zpHgvSqxAcbBIGIUKGAQ gCSl+x6T+ZpY3bOiPEr2tB+oQPvDGOtfBTaufveOOQlLz4kaMrA8p2W0XBc1hmqJFL 0J44vcu4NtkXg== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v3 00/10] KVM: selftests: Stress save+restore and #PF (ft. nested) Date: Mon, 29 Jun 2026 18:37:35 +0000 Message-ID: <20260629183746.699840-1-yosry@kernel.org> X-Mailer: git-send-email 2.55.0.rc0.799.gd6f94ed593-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 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 (7-10) 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. 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/ Yosry Ahmed (10): KVM: selftests: Move STR() and XSTR() definitions to test_util.h KVM: selftests: Fix RAX and RFLAGS VMCB offsets when running L2 KVM: selftests: Use an array for guest_regs (and fix offsets) 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 + .../testing/selftests/kvm/include/test_util.h | 3 + .../testing/selftests/kvm/include/x86/evmcs.h | 40 +-- .../selftests/kvm/include/x86/processor.h | 55 ++- tools/testing/selftests/kvm/include/x86/vmx.h | 63 ++-- .../testing/selftests/kvm/lib/x86/processor.c | 2 + tools/testing/selftests/kvm/lib/x86/svm.c | 60 ++-- tools/testing/selftests/kvm/lib/x86/ucall.c | 32 +- .../kvm/x86/evmcs_smm_controls_test.c | 3 - tools/testing/selftests/kvm/x86/smm_test.c | 3 - .../kvm/x86/stress_save_restore_pf_test.c | 326 ++++++++++++++++++ 11 files changed, 441 insertions(+), 147 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86/stress_save_restore_pf_test.c base-commit: 50406d35f5635e1cc523e61409d57e851b5f5df8 -- 2.55.0.rc0.799.gd6f94ed593-goog