linux-kernel - Re: [PATCH v3 03/14] x86/svm: Cleanup selective cr0 write intercept test

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Message-ID: <3cbc2be4-11f4-4ff2-989c-8bf7083c0f0e@amd.com>
Date: Wed, 12 Nov 2025 19:18:28 +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 03/14] x86/svm: Cleanup selective cr0 write intercept
 test

On 11/11/2025 4:56 AM, Yosry Ahmed wrote:
> Rename the test and functions to more general names describing the test
> more accurately. Use X86_CR0_CD instead of hardcoding the bitmask, and
> explicitly clear the bit in the prepare() function to make it clearer
> that it would only be set by the test.
> 
> Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
> ---
>  x86/svm_tests.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/x86/svm_tests.c b/x86/svm_tests.c
> index 80d5aeb108650..e911659194b3d 100644
> --- a/x86/svm_tests.c
> +++ b/x86/svm_tests.c
> @@ -793,23 +793,19 @@ static bool check_asid_zero(struct svm_test *test)
>  	return vmcb->control.exit_code == SVM_EXIT_ERR;
>  }
>  
> -static void sel_cr0_bug_prepare(struct svm_test *test)
> +static void prepare_sel_cr0_intercept(struct svm_test *test)
>  {
> +	vmcb->save.cr0 &= ~X86_CR0_CD;
>  	vmcb->control.intercept |= (1ULL << INTERCEPT_SELECTIVE_CR0);
>  }
>  
> -static bool sel_cr0_bug_finished(struct svm_test *test)
> -{
> -	return true;
> -}
> -
> -static void sel_cr0_bug_test(struct svm_test *test)
> +static void test_sel_cr0_write_intercept(struct svm_test *test)
>  {
>  	unsigned long cr0;
>  
> -	/* read cr0, clear CD, and write back */
> +	/* read cr0, set CD, and write back */
>  	cr0  = read_cr0();
> -	cr0 |= (1UL << 30);
> +	cr0 |= X86_CR0_CD;
>  	write_cr0(cr0);
>  
>  	/*
> @@ -821,7 +817,7 @@ static void sel_cr0_bug_test(struct svm_test *test)
>  	exit(report_summary());
>  }
>  
> -static bool sel_cr0_bug_check(struct svm_test *test)
> +static bool check_sel_cr0_intercept(struct svm_test *test)
>  {
>  	return vmcb->control.exit_code == SVM_EXIT_CR0_SEL_WRITE;
>  }
> @@ -3486,9 +3482,9 @@ 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_bug", default_supported, sel_cr0_bug_prepare,
> -	  default_prepare_gif_clear, sel_cr0_bug_test,
> -	  sel_cr0_bug_finished, sel_cr0_bug_check },
> +	{ "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 },


LGTM

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

Tested on AMD Genoa machine. This test case works as expected.

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