Re: [PATCH v13 12/12] x86/kvm: Add guest support for detecting and enabling SEV Live Migration feature.

Borislav Petkov
2021-04-21T14:44:07Z

On Thu, Apr 15, 2021 at 04:01:16PM +0000, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
>
> The guest support for detecting and enabling SEV Live migration
> feature uses the following logic :
>
> - kvm_init_plaform() invokes check_kvm_sev_migration() which
> checks if its booted under the EFI
>
> - If not EFI,
>
> i) check for the KVM_FEATURE_CPUID

Where do you do that?

$ git grep KVM_FEATURE_CPUID
$

Do you mean

kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)

per chance?

> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 78bb0fae3982..94ef16d263a7 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -26,6 +26,7 @@
> #include <linux/kprobes.h>
> #include <linux/nmi.h>
> #include <linux/swait.h>
> +#include <linux/efi.h>
> #include <asm/timer.h>
> #include <asm/cpu.h>
> #include <asm/traps.h>
> @@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
> early_set_memory_decrypted((unsigned long) ptr, size);
> }
>
> +static int __init setup_kvm_sev_migration(void)

kvm_init_sev_migration() or so.

...

> @@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
>
> bool sev_enabled __section(".data");
>
> +bool sev_live_migration_enabled __section(".data");

Pls add a function called something like:

bool sev_feature_enabled(enum sev_feature)

and gets SEV_FEATURE_LIVE_MIGRATION and then use it instead of adding
yet another boolean which contains whether some aspect of SEV has been
enabled or not.

Then add a

static enum sev_feature sev_features;

in mem_encrypt.c and that function above will query that sev_features
enum for set flags.

Then, if you feel bored, you could convert sme_active, sev_active,
sev_es_active, mem_encrypt_active and whetever else code needs to query
any aspect of SEV being enabled or not, to that function.

> +void __init check_kvm_sev_migration(void)
> +{
> + if (sev_active() &&
> + kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {

Save an indentation level:

if (!sev_active() ||
!kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION))
return;

> + unsigned long nr_pages;
> + int i;
> +
> + pr_info("KVM enable live migration\n");

That should be at the end of the function and say:

pr_info("KVM live migration enabled.\n");

> + WRITE_ONCE(sev_live_migration_enabled, true);

Why WRITE_ONCE?

And that needs to go to the end of the function too.

Thx.

--
Regards/Gruss,
Boris.