[kvm-unit-tests v2 PATCH] vmx: Fix EPT accessed and dirty flag test

[kvm-unit-tests v2 PATCH] vmx: Fix EPT accessed and dirty flag test

[Cathy Avery]

If ept_ad is not supported by the processor or has been
turned off via kvm module param, test_ept_eptp() will
incorrectly leave EPTP_AD_FLAG set in variable eptp
causing the following failures of subsequent
test_vmx_valid_controls calls:

FAIL: Enable-EPT enabled; reserved bits [11:7] 0: vmlaunch succeeds
FAIL: Enable-EPT enabled; reserved bits [63:N] 0: vmlaunch succeeds

Signed-off-by: Cathy Avery <cavery@redhat.com>
---

* Changes in v2:

- Initialize vmcs EPTP to good values for page walk len
  and ept memory type.
- Restore eptp to known good values from eptp_saved
- Cleanup test_vmx_vmlaunch to generate clearer and
  more consolidated test reports.
  New format suggested by seanjc@google.com
---
 x86/vmx_tests.c | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 3d57ed6..1269829 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -3392,14 +3392,21 @@ static void test_vmx_vmlaunch(u32 xerror)
 	bool success = vmlaunch_succeeds();
 	u32 vmx_inst_err;
 
-	report(success == !xerror, "vmlaunch %s",
-	       !xerror ? "succeeds" : "fails");
-	if (!success && xerror) {
-		vmx_inst_err = vmcs_read(VMX_INST_ERROR);
+	if (!success)
+	vmx_inst_err = vmcs_read(VMX_INST_ERROR);
+
+	if (success && !xerror)
+		report_pass("VMLAUNCH succeeded as expected");
+	else if (success && xerror)
+		report_fail("VMLAUNCH succeeded unexpectedly, wanted VM-Fail with error code = %d",
+			    xerror);
+	else if (!success && !xerror)
+		report_fail("VMLAUNCH hit unexpected VM-Fail with error code = %d",
+			    vmx_inst_err);
+	else
 		report(vmx_inst_err == xerror,
-		       "VMX inst error is %d (actual %d)", xerror,
-		       vmx_inst_err);
-	}
+		       "VMLAUNCH hit VM-Fail as expected, wanted error code %d, got %d",
+		       xerror, vmx_inst_err);
 }
 
 /*
@@ -4707,12 +4714,11 @@ static void test_ept_eptp(void)
 {
 	u32 primary_saved = vmcs_read(CPU_EXEC_CTRL0);
 	u32 secondary_saved = vmcs_read(CPU_EXEC_CTRL1);
-	u64 eptp_saved = vmcs_read(EPTP);
 	u32 primary = primary_saved;
 	u32 secondary = secondary_saved;
-	u64 eptp = eptp_saved;
 	u32 i, maxphysaddr;
 	u64 j, resv_bits_mask = 0;
+	u64 eptp_saved, eptp;
 
 	if (!((ctrl_cpu_rev[0].clr & CPU_SECONDARY) &&
 	    (ctrl_cpu_rev[1].clr & CPU_EPT))) {
@@ -4720,6 +4726,9 @@ static void test_ept_eptp(void)
 		return;
 	}
 
+	setup_dummy_ept();
+	eptp = eptp_saved = vmcs_read(EPTP);
+
 	/* Support for 4-level EPT is mandatory. */
 	report(is_4_level_ept_supported(), "4-level EPT support check");
 
@@ -4742,8 +4751,7 @@ static void test_ept_eptp(void)
 			test_vmx_invalid_controls();
 		report_prefix_pop();
 	}
-
-	eptp = (eptp & ~EPT_MEM_TYPE_MASK) | 6ul;
+	eptp = eptp_saved;
 
 	/*
 	 * Page walk length (bits 5:3).  Note, the value in VMCS.EPTP "is 1
@@ -4762,9 +4770,7 @@ static void test_ept_eptp(void)
 			test_vmx_invalid_controls();
 		report_prefix_pop();
 	}
-
-	eptp = (eptp & ~EPTP_PG_WALK_LEN_MASK) |
-	    3ul << EPTP_PG_WALK_LEN_SHIFT;
+	eptp = eptp_saved;
 
 	/*
 	 * Accessed and dirty flag (bit 6)
@@ -4784,6 +4790,7 @@ static void test_ept_eptp(void)
 		eptp |= EPTP_AD_FLAG;
 		test_eptp_ad_bit(eptp, false);
 	}
+	eptp = eptp_saved;
 
 	/*
 	 * Reserved bits [11:7] and [63:N]
@@ -4802,8 +4809,7 @@ static void test_ept_eptp(void)
 			test_vmx_invalid_controls();
 		report_prefix_pop();
 	}
-
-	eptp = (eptp & ~(EPTP_RESERV_BITS_MASK << EPTP_RESERV_BITS_SHIFT));
+	eptp = eptp_saved;
 
 	maxphysaddr = cpuid_maxphyaddr();
 	for (i = 0; i < (63 - maxphysaddr + 1); i++) {
@@ -4822,6 +4828,7 @@ static void test_ept_eptp(void)
 			test_vmx_invalid_controls();
 		report_prefix_pop();
 	}
+	eptp = eptp_saved;
 
 	secondary &= ~(CPU_EPT | CPU_URG);
 	vmcs_write(CPU_EXEC_CTRL1, secondary);
-- 
2.31.1

Re: [kvm-unit-tests v2 PATCH] vmx: Fix EPT accessed and dirty flag test

[Sean Christopherson]

On Wed, Feb 02, 2022, Cathy Avery wrote:
> If ept_ad is not supported by the processor or has been
> turned off via kvm module param, test_ept_eptp() will
> incorrectly leave EPTP_AD_FLAG set in variable eptp
> causing the following failures of subsequent
> test_vmx_valid_controls calls:
> 
> FAIL: Enable-EPT enabled; reserved bits [11:7] 0: vmlaunch succeeds
> FAIL: Enable-EPT enabled; reserved bits [63:N] 0: vmlaunch succeeds

Heh, the changelog never actually provides info on how it fixes things.

  Use the saved EPTP to restore the EPTP after each sub-test instead of
  manually unwinding what was done by the sub-test, which is error prone
  and hard to follow.

  Explicitly setup a dummy EPTP, as calling the test in isolation will cause
  test failures due to lack a good starting EPTP.

> Signed-off-by: Cathy Avery <cavery@redhat.com>
> ---
> 
> * Changes in v2:
> 
> - Initialize vmcs EPTP to good values for page walk len
>   and ept memory type.
> - Restore eptp to known good values from eptp_saved
> - Cleanup test_vmx_vmlaunch to generate clearer and
>   more consolidated test reports.
>   New format suggested by seanjc@google.com
> ---
>  x86/vmx_tests.c | 39 +++++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index 3d57ed6..1269829 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -3392,14 +3392,21 @@ static void test_vmx_vmlaunch(u32 xerror)
>  	bool success = vmlaunch_succeeds();
>  	u32 vmx_inst_err;
>  
> -	report(success == !xerror, "vmlaunch %s",
> -	       !xerror ? "succeeds" : "fails");
> -	if (!success && xerror) {
> -		vmx_inst_err = vmcs_read(VMX_INST_ERROR);
> +	if (!success)
> +	vmx_inst_err = vmcs_read(VMX_INST_ERROR);
> +
> +	if (success && !xerror)
> +		report_pass("VMLAUNCH succeeded as expected");
> +	else if (success && xerror)
> +		report_fail("VMLAUNCH succeeded unexpectedly, wanted VM-Fail with error code = %d",
> +			    xerror);
> +	else if (!success && !xerror)
> +		report_fail("VMLAUNCH hit unexpected VM-Fail with error code = %d",
> +			    vmx_inst_err);
> +	else
>  		report(vmx_inst_err == xerror,
> -		       "VMX inst error is %d (actual %d)", xerror,
> -		       vmx_inst_err);
> -	}
> +		       "VMLAUNCH hit VM-Fail as expected, wanted error code %d, got %d",
> +		       xerror, vmx_inst_err);
>  }

The changes to test_vmx_vmlaunch() need to be a separate patch.  The addition of
setup_dummy_ept() would ideally be separate as well, though I don't care terribly
about that one.

With this split in two (or three) and an updated changelog,

Reviewed-by: Sean Christopherson <seanjc@google.com>