Re: [kvm-unit-tests PATCH 1/2] nVMX: Restore active host RIP/CR4 after test_host_addr_size()

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Wed, Jul 15, 2020 at 11:34:46AM -0700, Krish Sadhukhan wrote:
> 
> On 7/13/20 5:23 PM, Sean Christopherson wrote:
> >Perform one last VMX transition to actually load the host's RIP and CR4
> >at the end of test_host_addr_size().  Simply writing the VMCS doesn't
> >restore the values in hardware, e.g. as is, CR4.PCIDE can be left set,
> >which causes spectacularly confusing explosions when other misguided
> >tests assume setting bit 63 in CR3 will cause a non-canonical #GP.
> >
> >Fixes: 0786c0316ac05 ("kvm-unit-test: nVMX: Check Host Address Space Size on vmentry of nested guests")
> >Cc: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> >Cc: Karl Heubaum <karl.heubaum@oracle.com>
> >Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> >---
> >  x86/vmx_tests.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> >diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> >index 29f3d0e..cb42a2d 100644
> >--- a/x86/vmx_tests.c
> >+++ b/x86/vmx_tests.c
> >@@ -7673,6 +7673,11 @@ static void test_host_addr_size(void)
> >  		vmcs_write(ENT_CONTROLS, entry_ctrl_saved | ENT_GUEST_64);
> >  		vmcs_write(HOST_RIP, rip_saved);
> >  		vmcs_write(HOST_CR4, cr4_saved);
> >+
> >+		/* Restore host's active RIP and CR4 values. */
> >+		report_prefix_pushf("restore host state");
> >+		test_vmx_vmlaunch(0);
> >+		report_prefix_pop();
> >  	}
> >  }
> Just for my understanding.  When you say, "other misguided tests", which
> tests are you referring to ?  In the current sequence of tests in
> vmx_host_state_area_test(), test_load_host_perf_global_ctrl() is the  one
> that follows and it runs fine.

See test_mtf_guest() in patch 2/2.  https://patchwork.kernel.org/patch/11661189/