[svsm-devel] [PATCH v3 13/14] x86/sev: Hide SVSM attestation entries if not running under an SVSM
Kuppuswamy Sathyanarayanan
sathyanarayanan.kuppuswamy at linux.intel.com
Mon Apr 15 21:48:53 CEST 2024
Hi,
On 4/15/24 12:16 PM, Tom Lendacky wrote:
> On 4/12/24 10:52, Tom Lendacky wrote:
>> On 4/9/24 13:12, Kuppuswamy Sathyanarayanan wrote:
>>> On 3/25/24 3:26 PM, Tom Lendacky wrote:
>>>> Config-fs provides support to hide individual attribute entries. Using
>>>> this support, base the display of the SVSM related entries on the presence
>>>> of an SVSM.
>>>>
>>>> Cc: Joel Becker <jlbec at evilplan.org>
>>>> Cc: Christoph Hellwig <hch at lst.de>
>>>> Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
>>>> ---
>>>> arch/x86/coco/core.c | 4 ++++
>>>> drivers/virt/coco/tsm.c | 14 ++++++++++----
>>>> include/linux/cc_platform.h | 8 ++++++++
>>>> 3 files changed, 22 insertions(+), 4 deletions(-)
>>>>
>
>>>
>>> Any comment about the following query? I think introducing a CC flag for this use
>>> case is over kill.
>>>
>>> https://lore.kernel.org/lkml/6b90b223-46e0-4e6d-a17c-5caf72e3c949@linux.intel.com/
>>
>> If you don't think TDX will be able to make use of the SVSM attribute I can look at adding a callback. But I was waiting to see if anyone else had comments, for or against, before re-doing it all.
>>
>
> What about something like this (applied on top of patch 13):
>
> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
> index efa0f648f754..d07be9d05cd0 100644
> --- a/arch/x86/coco/core.c
> +++ b/arch/x86/coco/core.c
> @@ -12,7 +12,6 @@
>
> #include <asm/coco.h>
> #include <asm/processor.h>
> -#include <asm/sev.h>
>
> enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
> u64 cc_mask __ro_after_init;
> @@ -79,9 +78,6 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
> case CC_ATTR_GUEST_STATE_ENCRYPT:
> return sev_status & MSR_AMD64_SEV_ES_ENABLED;
>
> - case CC_ATTR_GUEST_SVSM_PRESENT:
> - return snp_get_vmpl();
> -
> /*
> * With SEV, the rep string I/O instructions need to be unrolled
> * but SEV-ES supports them through the #VC handler.
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 0d2c9926a97c..68c881a50026 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -1036,6 +1036,17 @@ static int sev_report_new(struct tsm_report *report, void *data)
> return 0;
> }
>
> +static bool sev_tsm_visibility(enum tsm_type type)
> +{
> + /* Check for SVSM-related attributes */
> + switch (type) {
> + case TSM_TYPE_SERVICE_PROVIDER:
> + return snp_get_vmpl();
> + default:
> + return false;
> + }
> +}
> +
> static struct tsm_ops sev_tsm_ops = {
> .name = KBUILD_MODNAME,
> .report_new = sev_report_new,
> @@ -1126,7 +1137,8 @@ static int __init sev_guest_probe(struct platform_device *pdev)
> /* Set the privlevel_floor attribute based on the current VMPL */
> sev_tsm_ops.privlevel_floor = snp_get_vmpl();
>
> - ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_extra_type);
> + ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_extra_type,
> + sev_tsm_visibility);
> if (ret)
> goto e_free_cert_data;
>
> diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
> index 1253bf76b570..0fd8e60d7bee 100644
> --- a/drivers/virt/coco/tdx-guest/tdx-guest.c
> +++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
> @@ -301,7 +301,7 @@ static int __init tdx_guest_init(void)
> goto free_misc;
> }
>
> - ret = tsm_register(&tdx_tsm_ops, NULL, NULL);
> + ret = tsm_register(&tdx_tsm_ops, NULL, NULL, NULL);
> if (ret)
> goto free_quote;
>
> diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
> index d30471874e87..e73840aed13d 100644
> --- a/drivers/virt/coco/tsm.c
> +++ b/drivers/virt/coco/tsm.c
> @@ -16,6 +16,7 @@ static struct tsm_provider {
> const struct tsm_ops *ops;
> const struct config_item_type *type;
> void *data;
> + tsm_visibility_t visibility;
> } provider;
> static DECLARE_RWSEM(tsm_rwsem);
>
> @@ -64,10 +65,13 @@ static struct tsm_report_state *to_state(struct tsm_report *report)
> return container_of(report, struct tsm_report_state, report);
> }
>
> -static bool provider_visibility(const struct config_item *item,
> - const struct configfs_attribute *attr)
> +static bool service_provider_visibility(const struct config_item *item,
> + const struct configfs_attribute *attr)
> {
> - return cc_platform_has(CC_ATTR_GUEST_SVSM_PRESENT);
> + if (!provider.visibility)
> + return true;
> +
> + return provider.visibility(TSM_TYPE_SERVICE_PROVIDER);
> }
>
> static int try_advance_write_generation(struct tsm_report *report)
> @@ -150,7 +154,7 @@ static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
>
> return len;
> }
> -CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_provider, provider_visibility);
> +CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_provider, service_provider_visibility);
>
> static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
> const char *buf, size_t len)
> @@ -171,7 +175,7 @@ static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
>
> return len;
> }
> -CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_guid, provider_visibility);
> +CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_guid, service_provider_visibility);
>
> static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
> const char *buf, size_t len)
> @@ -192,7 +196,7 @@ static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg
>
> return len;
> }
> -CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_manifest_version, provider_visibility);
> +CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_manifest_version, service_provider_visibility);
>
> static ssize_t tsm_report_inblob_write(struct config_item *cfg,
> const void *buf, size_t count)
> @@ -339,7 +343,8 @@ static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
>
> return tsm_report_read(report, buf, count, TSM_MANIFEST);
> }
> -CONFIGFS_BIN_ATTR_VISIBLE_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX, provider_visibility);
> +CONFIGFS_BIN_ATTR_VISIBLE_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX,
> + service_provider_visibility);
>
> #define TSM_DEFAULT_ATTRS() \
> &tsm_report_attr_generation, \
> @@ -449,7 +454,8 @@ static struct configfs_subsystem tsm_configfs = {
> };
>
> int tsm_register(const struct tsm_ops *ops, void *priv,
> - const struct config_item_type *type)
> + const struct config_item_type *type,
> + tsm_visibility_t visibility)
> {
> const struct tsm_ops *conflict;
>
> @@ -468,6 +474,7 @@ int tsm_register(const struct tsm_ops *ops, void *priv,
> provider.ops = ops;
> provider.data = priv;
> provider.type = type;
> + provider.visibility = visibility;
> return 0;
> }
> EXPORT_SYMBOL_GPL(tsm_register);
> @@ -480,6 +487,7 @@ int tsm_unregister(const struct tsm_ops *ops)
> provider.ops = NULL;
> provider.data = NULL;
> provider.type = NULL;
> + provider.visibility = NULL;
> return 0;
> }
> EXPORT_SYMBOL_GPL(tsm_unregister);
> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> index f1b4266c1484..cb0d6cd1c12f 100644
> --- a/include/linux/cc_platform.h
> +++ b/include/linux/cc_platform.h
> @@ -90,14 +90,6 @@ enum cc_attr {
> * Examples include TDX Guest.
> */
> CC_ATTR_HOTPLUG_DISABLED,
> -
> - /**
> - * @CC_ATTR_GUEST_SVSM_PRESENT: Guest is running under an SVSM
> - *
> - * The platform/OS is running as a guest/virtual machine and is
> - * running under a Secure VM Service Module (SVSM).
> - */
> - CC_ATTR_GUEST_SVSM_PRESENT,
> };
>
> #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> diff --git a/include/linux/tsm.h b/include/linux/tsm.h
> index 27cc97fe8dcd..5aaf626d178d 100644
> --- a/include/linux/tsm.h
> +++ b/include/linux/tsm.h
> @@ -74,7 +74,20 @@ extern const struct config_item_type tsm_report_default_type;
> /* publish @privlevel, @privlevel_floor, and @auxblob attributes */
> extern const struct config_item_type tsm_report_extra_type;
>
> +/*
> + * Used to indicate the attribute group type to the visibility callback to
> + * avoid the callback having to examine the attribute name.
Checking the attribute name will give more flexibility, right? Since it is one time
check, it should not be costly, right?
> +enum tsm_type {
> + TSM_TYPE_SERVICE_PROVIDER,
> +
> + TSM_TYPE_MAX
> +};
> +
> +typedef bool (*tsm_visibility_t)(enum tsm_type type);
> +
> int tsm_register(const struct tsm_ops *ops, void *priv,
> - const struct config_item_type *type);
> + const struct config_item_type *type,
> + tsm_visibility_t visibility);
> int tsm_unregister(const struct tsm_ops *ops);
> #endif /* __TSM_H */
>
Why not add a callback in tsm_ops?
>> Thanks,
>> Tom
>>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
More information about the Svsm-devel
mailing list