From nobody Sun Feb 8 22:48:53 2026 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 0D65A341648 for ; Mon, 10 Nov 2025 23:27:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762817241; cv=none; b=hyjofjTxPGbnK5j21u5CGYl28P+HYG1kzVJnk93h9TvQ8sRKOI9/vBHnHriAIwjytu5rN++qxo/WseuzJ0k3BU/G+6I2eEH5A6WDDZNqfmG8PCHwtlRByDXMBrG+6jWyxJPtqGwqFzb2zQxELf41aq5RRMwzh/RWrmyIogIuVSg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762817241; c=relaxed/simple; bh=kuLUgZpETFRjmpsSenbVTCVPBEIi0OzIVA9pTK+b1Xk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FFytCxBa/6BhWBIh78XOU6+Sb8sK/SaMCVxhYRfFFsdwFvoNtBh3PFdOF0CFRp+dSvL95+lW88gx4zxORj8eaQri9yIrThq7aq3yZQpXkcGMBftwUXUJHxtlAV6g2xIDF73SgyGIbzhqWHXC7QlusYMZkiLymeX6nCc3vaC2auw= 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=VTrWYeak; arc=none smtp.client-ip=91.218.175.178 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="VTrWYeak" 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=1762817238; 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: in-reply-to:in-reply-to:references:references; bh=4JXklTZXG2BQ9ptOoEb+PXLCGrKmuijPP72hNX/U+YI=; b=VTrWYeakq+VPHDdVm62Sd2Wqma0TNFEzuPwDO4ZzWfNmeaFHWJB68JF/ZUNsuZ3c4vfMHI o27aGU1gF2DdgaV7cuA0VqhNI3EncyGO40TwQwwJ4tXxmRP1egxFS4LOtK3WqsLdL9dmwi eEn703H+Yig+ZVZRgLLIdh8YINVXmJQ= From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , Kevin Cheng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v3 10/14] x86/svm: Generalize and improve selective CR0 write intercept test Date: Mon, 10 Nov 2025 23:26:38 +0000 Message-ID: <20251110232642.633672-11-yosry.ahmed@linux.dev> In-Reply-To: <20251110232642.633672-1-yosry.ahmed@linux.dev> References: <20251110232642.633672-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" In preparation for adding more test cases, make the test easier to extend. Create a generic helper that sets an arbitrary bit in CR0, optionally using FEP. The helper also stores the value to be written in test->scratch, making it possible to double check if the write was actually executed or not. Use report_svm_guest() instead of report_fail() + exit(). Make test_sel_cr0_write_intercept() use the generic helper, and add another test case that sets FEP to exercise the interception path in the emulator. Finally, in check_sel_cr0_intercept() also check that the write was not executed by comparing CR0 value in the VMCB12 with the value-to-be-written stored in test->scratch. Signed-off-by: Yosry Ahmed --- x86/svm_tests.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/x86/svm_tests.c b/x86/svm_tests.c index 1e7556a37adec..7e292a9a7b4ec 100644 --- a/x86/svm_tests.c +++ b/x86/svm_tests.c @@ -133,27 +133,36 @@ static void prepare_sel_cr0_intercept(struct svm_test= *test) vmcb->control.intercept |=3D (1ULL << INTERCEPT_SELECTIVE_CR0); } =20 -static void test_sel_cr0_write_intercept(struct svm_test *test) +static void __test_cr0_write_bit(struct svm_test *test, unsigned long bit, + bool intercept, bool fep) { unsigned long cr0; =20 - /* read cr0, set CD, and write back */ - cr0 =3D read_cr0(); - cr0 |=3D X86_CR0_CD; - write_cr0(cr0); + cr0 =3D read_cr0(); + cr0 |=3D bit; + test->scratch =3D cr0; =20 - /* - * If we are here the test failed, not sure what to do now because we - * are not in guest-mode anymore so we can't trigger an intercept. - * Trigger a tripple-fault for now. - */ - report_fail("sel_cr0 test. Can not recover from this - exiting"); - exit(report_summary()); + asm_conditional_fep_safe(fep, "mov %0,%%cr0", "r"(cr0)); + + /* This code should be unreachable when an intercept is expected */ + report_svm_guest(!intercept, test, "Expected intercept on CR0 write"); +} + +/* MOV-to-CR0 updating CR0.CD is intercepted by the selective intercept */ +static void test_sel_cr0_write_intercept(struct svm_test *test) +{ + __test_cr0_write_bit(test, X86_CR0_CD, true, false); +} + +static void test_sel_cr0_write_intercept_emul(struct svm_test *test) +{ + __test_cr0_write_bit(test, X86_CR0_CD, true, true); } =20 static bool check_sel_cr0_intercept(struct svm_test *test) { - return vmcb->control.exit_code =3D=3D SVM_EXIT_CR0_SEL_WRITE; + return vmcb->control.exit_code =3D=3D SVM_EXIT_CR0_SEL_WRITE && + vmcb->save.cr0 !=3D test->scratch; } =20 static void prepare_cr3_intercept(struct svm_test *test) @@ -3461,6 +3470,9 @@ struct svm_test svm_tests[] =3D { { "sel cr0 write intercept", default_supported, prepare_sel_cr0_intercept, default_prepare_gif_clear, test_sel_cr0_write_intercept, default_finished, check_sel_cr0_intercept= }, + { "sel cr0 write intercept emulate", fep_supported, + prepare_sel_cr0_intercept, default_prepare_gif_clear, + test_sel_cr0_write_intercept_emul, default_finished, check_sel_cr0_inte= rcept}, { "cr3 read intercept", default_supported, prepare_cr3_intercept, default_prepare_gif_clear, test_cr3_intercept, default_finished, check_cr3_intercept }, --=20 2.51.2.1041.gc1ab5b90ca-goog