linux-kernel - Re: [PATCH v3 04/14] x86/svm: Move CR0 selective write intercept test near CR3 intercept

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Message-ID: <a3163ebf-86bd-42b7-a413-7a936a6a92d1@amd.com>
Date: Wed, 12 Nov 2025 19:22:43 +0530
From: Manali Shukla <manali.shukla@....com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>, Sean Christopherson
	<seanjc@...gle.com>
CC: Paolo Bonzini <pbonzini@...hat.com>, Kevin Cheng <chengkev@...gle.com>,
	<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 04/14] x86/svm: Move CR0 selective write intercept test
 near CR3 intercept

On 11/11/2025 4:56 AM, Yosry Ahmed wrote:
> It makes more semantic sense for these tests to be in close proximity.
> 
> Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
> ---
>  x86/svm_tests.c | 64 ++++++++++++++++++++++++-------------------------
>  1 file changed, 32 insertions(+), 32 deletions(-)
> 
> diff --git a/x86/svm_tests.c b/x86/svm_tests.c
> index e911659194b3d..feeb27d61435b 100644
> --- a/x86/svm_tests.c
> +++ b/x86/svm_tests.c
> @@ -112,6 +112,35 @@ static bool finished_rsm_intercept(struct svm_test *test)
>  	return get_test_stage(test) == 2;
>  }
>  
> +static void prepare_sel_cr0_intercept(struct svm_test *test)
> +{
> +	vmcb->save.cr0 &= ~X86_CR0_CD;
> +	vmcb->control.intercept |= (1ULL << INTERCEPT_SELECTIVE_CR0);
> +}
> +
> +static void test_sel_cr0_write_intercept(struct svm_test *test)
> +{
> +	unsigned long cr0;
> +
> +	/* read cr0, set CD, and write back */
> +	cr0  = read_cr0();
> +	cr0 |= X86_CR0_CD;
> +	write_cr0(cr0);
> +
> +	/*
> +	 * 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());
> +}
> +
> +static bool check_sel_cr0_intercept(struct svm_test *test)
> +{
> +	return vmcb->control.exit_code == SVM_EXIT_CR0_SEL_WRITE;
> +}
> +
>  static void prepare_cr3_intercept(struct svm_test *test)
>  {
>  	default_prepare(test);
> @@ -793,35 +822,6 @@ static bool check_asid_zero(struct svm_test *test)
>  	return vmcb->control.exit_code == SVM_EXIT_ERR;
>  }
>  
> -static void prepare_sel_cr0_intercept(struct svm_test *test)
> -{
> -	vmcb->save.cr0 &= ~X86_CR0_CD;
> -	vmcb->control.intercept |= (1ULL << INTERCEPT_SELECTIVE_CR0);
> -}
> -
> -static void test_sel_cr0_write_intercept(struct svm_test *test)
> -{
> -	unsigned long cr0;
> -
> -	/* read cr0, set CD, and write back */
> -	cr0  = read_cr0();
> -	cr0 |= X86_CR0_CD;
> -	write_cr0(cr0);
> -
> -	/*
> -	 * 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());
> -}
> -
> -static bool check_sel_cr0_intercept(struct svm_test *test)
> -{
> -	return vmcb->control.exit_code == SVM_EXIT_CR0_SEL_WRITE;
> -}
> -
>  #define TSC_ADJUST_VALUE    (1ll << 32)
>  #define TSC_OFFSET_VALUE    (~0ull << 48)
>  static bool ok;
> @@ -3458,6 +3458,9 @@ struct svm_test svm_tests[] = {
>  	{ "rsm", default_supported,
>  	  prepare_rsm_intercept, default_prepare_gif_clear,
>  	  test_rsm_intercept, finished_rsm_intercept, check_rsm_intercept },
> +	{ "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},
>  	{ "cr3 read intercept", default_supported,
>  	  prepare_cr3_intercept, default_prepare_gif_clear,
>  	  test_cr3_intercept, default_finished, check_cr3_intercept },
> @@ -3482,9 +3485,6 @@ struct svm_test svm_tests[] = {
>  	{ "asid_zero", default_supported, prepare_asid_zero,
>  	  default_prepare_gif_clear, test_asid_zero,
>  	  default_finished, check_asid_zero },
> -	{ "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},
>  	{ "tsc_adjust", tsc_adjust_supported, tsc_adjust_prepare,
>  	  default_prepare_gif_clear, tsc_adjust_test,
>  	  default_finished, tsc_adjust_check },

You might probably want to add "No functional change intended" in the
commit message, since this is just the movement of a test case.

Reviewed-by: Manali Shukla <manali.shukla@....com>