On Wed, Feb 20, 2019 at 6:24 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> ...to document why there are two variations of "setup EPT" and when to
> employ each variant.
>
> Suggested-by: Marc Orr <marcorr@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> x86/vmx_tests.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index 9db2f2f..d800647 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -1004,6 +1004,17 @@ static int insn_intercept_exit_handler(void)
> return VMX_TEST_RESUME;
> }
>
> +/**
> + * __setup_ept - Setup the VMCS fields to enable Extended Page Tables (EPT)
> + * @hpa: Host physical address of the top-level, a.k.a. root, EPT table
> + * @enable_ad: Whether or not to enable Access/Dirty bits for EPT entries
> + *
> + * Returns 0 on success, 1 on failure.
> + *
> + * Note that @hpa doesn't need to point at actual memory if VM-Launch is
> + * expected to fail, e.g. setup_dummy_ept() arbitrarily passes '0' to satisfy
> + * the various EPTP consistency checks, but doesn't ensure backing for HPA '0'.
> + */
> static int __setup_ept(u64 hpa, bool enable_ad)
> {
> if (!(ctrl_cpu_rev[0].clr & CPU_SECONDARY) ||
> @@ -1033,7 +1044,15 @@ static int __setup_ept(u64 hpa, bool enable_ad)
> return 0;
> }
>
> -/* Enables EPT and sets up the identity map. */
> +/**
> + * setup_ept - Enable Extended Page Tables (EPT) and setup an identity map
> + * @enable_ad: Whether or not to enable Access/Dirty bits for EPT entries
> + *
> + * Returns 0 on success, 1 on failure.
> + *
> + * This is the "real" function for setting up EPT tables, i.e. use this for
> + * tests that need to run code in the guest with EPT enabled.
> + */
> static int setup_ept(bool enable_ad)
> {
> unsigned long end_of_memory;
> @@ -1057,6 +1076,14 @@ static int setup_ept(bool enable_ad)
> return 0;
> }
>
> +/**
> + * setup_dummy_ept - Enable Extended Page Tables (EPT) with a dummy root HPA
> + *
> + * Setup EPT using a semi-arbitrary dummy root HPA. This function is intended
> + * for use by tests that need EPT enabled to verify dependent VMCS controls
> + * but never expect to fully enter the guest, i.e. don't need setup the actual
> + * EPT tables.
> + */
> static void setup_dummy_ept(void)
> {
> if (__setup_ept(0, false))
> --
> 2.20.1
>
Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx>
