On 2/20/2025 3:37 PM, Dionna Amalie Glaze wrote:

On Thu, Feb 20, 2025 at 12:07 PM Kalra, Ashish [off-list ref] wrote:

quoted

Hello Dionna,

On 2/20/2025 10:44 AM, Dionna Amalie Glaze wrote:

quoted

On Wed, Feb 19, 2025 at 12:53 PM Ashish Kalra [off-list ref] wrote:

quoted

From: Ashish Kalra <ashish.kalra@amd.com>

Modify the behavior of implicit SEV initialization in some of the
SEV ioctls to do both SEV initialization and shutdown and add
implicit SNP initialization and shutdown to some of the SNP ioctls
so that the change of SEV/SNP platform initialization not being
done during PSP driver probe time does not break userspace tools
such as sevtool, etc.

Prior to this patch, SEV has always been initialized before these
ioctls as SEV initialization is done as part of PSP module probe,
but now with SEV initialization being moved to KVM module load instead
of PSP driver probe, the implied SEV INIT actually makes sense and gets
used and additionally to maintain SEV platform state consistency
before and after the ioctl SEV shutdown needs to be done after the
firmware call.

It is important to do SEV Shutdown here with the SEV/SNP initialization
moving to KVM, an implicit SEV INIT here as part of the SEV ioctls not
followed with SEV Shutdown will cause SEV to remain in INIT state and
then a future SNP INIT in KVM module load will fail.

Similarly, prior to this patch, SNP has always been initialized before
these ioctls as SNP initialization is done as part of PSP module probe,
therefore, to keep a consistent behavior, SNP init needs to be done
here implicitly as part of these ioctls followed with SNP shutdown
before returning from the ioctl to maintain the consistent platform
state before and after the ioctl.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 drivers/crypto/ccp/sev-dev.c | 117 ++++++++++++++++++++++++++++-------
 1 file changed, 93 insertions(+), 24 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 8f5c474b9d1c..b06f43eb18f7 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c

@@ -1461,7 +1461,8 @@ static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp)
 static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp, bool writable)
 {
        struct sev_device *sev = psp_master->sev_data;
-       int rc;
+       bool shutdown_required = false;
+       int rc, error;

        if (!writable)
                return -EPERM;

@@ -1470,19 +1471,26 @@ static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp, bool wr
                rc = __sev_platform_init_locked(&argp->error);
                if (rc)
                        return rc;
+               shutdown_required = true;
        }

-       return __sev_do_cmd_locked(cmd, NULL, &argp->error);
+       rc = __sev_do_cmd_locked(cmd, NULL, &argp->error);
+
+       if (shutdown_required)
+               __sev_platform_shutdown_locked(&error);

This error is discarded. Is that by design? If so, It'd be better to
call this ignored_error.

This is by design, we cannot overwrite the error for the original command being issued
here which in this case is do_pek_pdh_gen, hence we use a local error for the shutdown command.
And __sev_platform_shutdown_locked() has it's own error logging code, so it will be printing
the error message for the shutdown command failure, so the shutdown error is not eventually
being ignored, that error log will assist in any inconsistent SEV/SNP platform state and
subsequent errors.

quoted

quoted

+
+       return rc;
 }

 static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
 {
        struct sev_device *sev = psp_master->sev_data;
        struct sev_user_data_pek_csr input;
+       bool shutdown_required = false;
        struct sev_data_pek_csr data;
        void __user *input_address;
        void *blob = NULL;
-       int ret;
+       int ret, error;

        if (!writable)
                return -EPERM;

@@ -1513,6 +1521,7 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
                ret = __sev_platform_init_locked(&argp->error);
                if (ret)
                        goto e_free_blob;
+               shutdown_required = true;
        }

        ret = __sev_do_cmd_locked(SEV_CMD_PEK_CSR, &data, &argp->error);

@@ -1531,6 +1540,9 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
        }

 e_free_blob:
+       if (shutdown_required)
+               __sev_platform_shutdown_locked(&error);

Another discarded error. This function is called in different
locations in sev-dev.c with and without checking the result, which
seems problematic.

Not really, if shutdown fails for any reason, the error is printed.
The return value here reflects the value of the original command/function.
The command/ioctl could have succeeded but the shutdown failed, hence,
shutdown error is printed, but the return value reflects that the ioctl succeeded.

Additionally, in case of INIT before the command is issued, the command may
have failed without the SEV state being in INIT state, hence the error for the
INIT command failure is returned back from the ioctl.

quoted

quoted

+
        kfree(blob);
        return ret;
 }

@@ -1747,8 +1759,9 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
        struct sev_device *sev = psp_master->sev_data;
        struct sev_user_data_pek_cert_import input;
        struct sev_data_pek_cert_import data;
+       bool shutdown_required = false;
        void *pek_blob, *oca_blob;
-       int ret;
+       int ret, error;

        if (!writable)
                return -EPERM;

@@ -1780,11 +1793,15 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp, bool writable)
                ret = __sev_platform_init_locked(&argp->error);
                if (ret)
                        goto e_free_oca;
+               shutdown_required = true;
        }

        ret = __sev_do_cmd_locked(SEV_CMD_PEK_CERT_IMPORT, &data, &argp->error);

 e_free_oca:
+       if (shutdown_required)
+               __sev_platform_shutdown_locked(&error);

Again.

quoted

+
        kfree(oca_blob);
 e_free_pek:
        kfree(pek_blob);

@@ -1901,17 +1918,8 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
        struct sev_data_pdh_cert_export data;
        void __user *input_cert_chain_address;
        void __user *input_pdh_cert_address;
-       int ret;
-
-       /* If platform is not in INIT state then transition it to INIT. */
-       if (sev->state != SEV_STATE_INIT) {
-               if (!writable)
-                       return -EPERM;
-
-               ret = __sev_platform_init_locked(&argp->error);
-               if (ret)
-                       return ret;
-       }
+       bool shutdown_required = false;
+       int ret, error;

        if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
                return -EFAULT;

@@ -1952,6 +1960,16 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
        data.cert_chain_len = input.cert_chain_len;

 cmd:
+       /* If platform is not in INIT state then transition it to INIT. */
+       if (sev->state != SEV_STATE_INIT) {
+               if (!writable)
+                       goto e_free_cert;
+               ret = __sev_platform_init_locked(&argp->error);

Using argp->error for init instead of the ioctl-requested command
means that the user will have difficulty distinguishing which process
is at fault, no?

Not really, in case the SEV command has still not been issued, argp->error is still usable
and returned back to the caller (no need to use a local error here), we are not overwriting
the argp->error used for the original command/ioctl here.

I mean in the case that argp->error is set to a value shared by the
command and init, it's hard to know what the problem was.
I'd like to ensure that the documentation is updated to reflect that
(in this case) if PDH_CERT_EXPORT returns INVALID_PLATFORM_STATE, then
it's because the platform was not in PSTATE.UNINIT state.
The new behavior of initializing when you need to now means that you
should have ruled out INVALID_PLATFORM_STATE as a possible value from
PDH_EXPORT_CERT. Same for SNP_CONFIG.

There is not a 1-to-1 mapping between the ioctl commands and the SEV
commands now, so I think you need extra documentation to clarify the
new error space for at least pdh_export and set_config

SNP_PLATFORM_STATUS, VLEK_LOAD, and SNP_COMMIT appear to not
necessarily have a provenance confusion after looking closer.

I am more of less trying to match the current behavior of sev_ioctl_do_pek_import()
or sev_ioctl_do_pdh_export().

All this is implementation specific handling so we can't update SEV/SNP firmware
API specs documentation for this new error space, this is not a firmware specific return code. 

But to maintain 1-to-1 mapping between the ioctl commands and the SEV/SNP commands, 
i think it will be better to handle this INIT in the same way as SHUTDOWN, which
is to use a local error for INIT and in case of implicit INIT failures, let the
error logs from __sev_platform_init_locked() OR __sev_snp_init_locked() be printed
and always return INVALID_PLATFORM_STATE as error back to the caller.

Thanks,
Ashish