by Tom Lendacky

[permalink] [raw]

Subject: Re: [PATCH 07/13] KVM: SVM: Append "_enabled" to module-scoped SEV/SEV-ES control variables

On 1/8/21 6:47 PM, Sean Christopherson wrote:
> Rename sev and sev_es to sev_enabled and sev_es_enabled respectively to
> better align with other KVM terminology, and to avoid pseudo-shadowing
> when the variables are moved to sev.c in a future patch ('sev' is often
> used for local struct kvm_sev_info pointers).
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <[email protected]>

Acked-by: Tom Lendacky <[email protected]>

> ---
> arch/x86/kvm/svm/sev.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 8ba93b8fa435..a024edabaca5 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -28,12 +28,12 @@
> #define __ex(x) __kvm_handle_fault_on_reboot(x)
>
> /* enable/disable SEV support */
> -static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> -module_param(sev, int, 0444);
> +static bool sev_enabled = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> +module_param_named(sev, sev_enabled, bool, 0444);
>
> /* enable/disable SEV-ES support */
> -static int sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> -module_param(sev_es, int, 0444);
> +static bool sev_es_enabled = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> +module_param_named(sev_es, sev_es_enabled, bool, 0444);
>
> static u8 sev_enc_bit;
> static int sev_flush_asids(void);
> @@ -213,7 +213,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>
> static int sev_es_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
> {
> - if (!sev_es)
> + if (!sev_es_enabled)
> return -ENOTTY;
>
> to_kvm_svm(kvm)->sev_info.es_active = true;
> @@ -1052,7 +1052,7 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> struct kvm_sev_cmd sev_cmd;
> int r;
>
> - if (!svm_sev_enabled() || !sev)
> + if (!svm_sev_enabled() || !sev_enabled)
> return -ENOTTY;
>
> if (!argp)
> @@ -1257,7 +1257,7 @@ void __init sev_hardware_setup(void)
> bool sev_es_supported = false;
> bool sev_supported = false;
>
> - if (!IS_ENABLED(CONFIG_KVM_AMD_SEV) || !sev)
> + if (!IS_ENABLED(CONFIG_KVM_AMD_SEV) || !sev_enabled)
> goto out;
>
> /* Does the CPU support SEV? */
> @@ -1294,7 +1294,7 @@ void __init sev_hardware_setup(void)
> sev_supported = true;
>
> /* SEV-ES support requested? */
> - if (!sev_es)
> + if (!sev_es_enabled)
> goto out;
>
> /* Does the CPU support SEV-ES? */
> @@ -1309,8 +1309,8 @@ void __init sev_hardware_setup(void)
> sev_es_supported = true;
>
> out:
> - sev = sev_supported;
> - sev_es = sev_es_supported;
> + sev_enabled = sev_supported;
> + sev_es_enabled = sev_es_supported;
> }
>
> void sev_hardware_teardown(void)
>

2021-01-13 03:11:21

by Sean Christopherson

[permalink] [raw]

Subject: Re: [PATCH 03/13] KVM: SVM: Move SEV module params/variables to sev.c

On Mon, Jan 11, 2021, Vitaly Kuznetsov wrote:
> Tom Lendacky <[email protected]> writes:
>
> > On 1/11/21 4:42 AM, Vitaly Kuznetsov wrote:
> >> Sean Christopherson <[email protected]> writes:
> >>
> >>> Unconditionally invoke sev_hardware_setup() when configuring SVM and
> >>> handle clearing the module params/variable 'sev' and 'sev_es' in
> >>> sev_hardware_setup(). This allows making said variables static within
> >>> sev.c and reduces the odds of a collision with guest code, e.g. the guest
> >>> side of things has already laid claim to 'sev_enabled'.
> >>>
> >>> Signed-off-by: Sean Christopherson <[email protected]>
> >>> ---
> >>> arch/x86/kvm/svm/sev.c | 11 +++++++++++
> >>> arch/x86/kvm/svm/svm.c | 15 +--------------
> >>> arch/x86/kvm/svm/svm.h | 2 --
> >>> 3 files changed, 12 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> >>> index 0eeb6e1b803d..8ba93b8fa435 100644
> >>> --- a/arch/x86/kvm/svm/sev.c
> >>> +++ b/arch/x86/kvm/svm/sev.c
> >>> @@ -27,6 +27,14 @@
> >>>
> >>> #define __ex(x) __kvm_handle_fault_on_reboot(x)
> >>>
> >>> +/* enable/disable SEV support */
> >>> +static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> >>> +module_param(sev, int, 0444);
> >>> +
> >>> +/* enable/disable SEV-ES support */
> >>> +static int sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
> >>> +module_param(sev_es, int, 0444);
> >>
> >> Two stupid questions (and not really related to your patch) for
> >> self-eduacation if I may:
> >>
> >> 1) Why do we rely on CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT (which
> >> sound like it control the guest side of things) to set defaults here?
> >
> > I thought it was a review comment, but I'm not able to find it now.
> >
> > Brijesh probably remembers better than me.
> >
> >>
> >> 2) It appears to be possible to do 'modprobe kvm_amd sev=0 sev_es=1' and
> >> this looks like a bogus configuration, should we make an effort to
> >> validate the correctness upon module load?
> >
> > This will still result in an overall sev=0 sev_es=0. Is the question just
> > about issuing a message based on the initial values specified?
> >
>
> Yes, as one may expect the result will be that SEV-ES guests work and
> plain SEV don't.

KVM doesn't issue messages when it overrides other module params due to
disable requirements, e.g. ept=0 unrestricted_guest=1 is roughly equivalent.
Not that what KVM currently does is right, but at least it's consistent. :-)

And on the other hand, I think it's reasonable to expect that specifying only
sev=0 is sufficient to disable both SEV and SEV-ES, e.g. to turn them off when
they're enabled by default.