Re: [PATCH 1/9] x86/hyperv: Add sev-snp enlightened guest static key

Vitaly Kuznetsov
2023-06-05T12:10:29Z

Tianyu Lan <ltykernel@gmail.com> writes:

> From: Tianyu Lan <tiala@microsoft.com>
>
> Introduce static key isolation_type_en_snp for enlightened
> sev-snp guest check.
>
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
> arch/x86/hyperv/ivm.c | 11 +++++++++++
> arch/x86/include/asm/mshyperv.h | 3 +++
> arch/x86/kernel/cpu/mshyperv.c | 8 ++++++--
> drivers/hv/hv_common.c | 6 ++++++
> include/asm-generic/mshyperv.h | 12 +++++++++---
> 5 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index cc92388b7a99..5d3ee3124e00 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -409,3 +409,14 @@ bool hv_isolation_type_snp(void)
> {
> return static_branch_unlikely(&isolation_type_snp);
> }
> +
> +DEFINE_STATIC_KEY_FALSE(isolation_type_en_snp);
> +/*
> + * hv_isolation_type_en_snp - Check system runs in the AMD SEV-SNP based
> + * isolation enlightened VM.
> + */
> +bool hv_isolation_type_en_snp(void)
> +{
> + return static_branch_unlikely(&isolation_type_en_snp);
> +}
> +
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 49bb4f2bd300..31c476f4e656 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -26,6 +26,7 @@
> union hv_ghcb;
>
> DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
> +DECLARE_STATIC_KEY_FALSE(isolation_type_en_snp);
>
> typedef int (*hyperv_fill_flush_list_func)(
> struct hv_guest_mapping_flush_list *flush,
> @@ -45,6 +46,8 @@ extern void *hv_hypercall_pg;
>
> extern u64 hv_current_partition_id;
>
> +extern bool hv_isolation_type_en_snp(void);
> +
> extern union hv_ghcb * __percpu *hv_ghcb_pg;
>
> int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index c7969e806c64..9186453251f7 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -402,8 +402,12 @@ static void __init ms_hyperv_init_platform(void)
> pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
> ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
>
> - if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
> +
> + if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
> + static_branch_enable(&isolation_type_en_snp);
> + } else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
> static_branch_enable(&isolation_type_snp);

Nitpick: In case 'isolation_type_snp' and 'isolation_type_en_snp' are
mutually exclusive, I'd suggest we rename the former: it is quite
un-intuitive that for an enlightened SNP guest '&isolation_type_snp' is
NOT enabled. E.g. we can use

'isol_type_snp_paravisor'
and
'isol_type_snp_enlightened'

(I also don't like 'isolation_type_en_snp' name as 'en' normally stands
for 'enabled')

> + }
> }
>
> if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
> @@ -473,7 +477,7 @@ static void __init ms_hyperv_init_platform(void)
>
> #if IS_ENABLED(CONFIG_HYPERV)
> if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
> - (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP))
> + ms_hyperv.paravisor_present)
> hv_vtom_init();
> /*
> * Setup the hook to get control post apic initialization.
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 64f9ceca887b..179bc5f5bf52 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -502,6 +502,12 @@ bool __weak hv_isolation_type_snp(void)
> }
> EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
>
> +bool __weak hv_isolation_type_en_snp(void)
> +{
> + return false;
> +}
> +EXPORT_SYMBOL_GPL(hv_isolation_type_en_snp);
> +
> void __weak hv_setup_vmbus_handler(void (*handler)(void))
> {
> }
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 402a8c1c202d..d444f831d633 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -36,15 +36,21 @@ struct ms_hyperv_info {
> u32 nested_features;
> u32 max_vp_index;
> u32 max_lp_index;
> - u32 isolation_config_a;
> + union {
> + u32 isolation_config_a;
> + struct {
> + u32 paravisor_present : 1;
> + u32 reserved1 : 31;
> + };
> + };
> union {
> u32 isolation_config_b;
> struct {
> u32 cvm_type : 4;
> - u32 reserved1 : 1;
> + u32 reserved2 : 1;
> u32 shared_gpa_boundary_active : 1;
> u32 shared_gpa_boundary_bits : 6;
> - u32 reserved2 : 20;
> + u32 reserved3 : 20;

Maybe use 'reserved_a1', 'reserved_b1', 'reserved_b2',... to avoid the
need to rename in the future when more bits from isolation_config_a get
used?

> };
> };
> u64 shared_gpa_boundary;

--
Vitaly