Re: [PATCH v5 08/10] KVM: SVM: move sev_issue_cmd_external_user to new API

[Tom Lendacky <thomas.lendacky@amd.com>]

On 11/7/24 17:24, Dionna Glaze wrote:
> ccp now prefers all calls from external drivers to dominate all calls
> into the driver on behalf of a user with a successful
> sev_check_external_user call.

Would it be simpler to have the new APIs take an fd for an argument,
instead of doing this rework?

Thanks,
Tom

> 
> CC: Sean Christopherson <seanjc@google.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: Dave Hansen <dave.hansen@linux.intel.com>
> CC: Ashish Kalra <ashish.kalra@amd.com>
> CC: Tom Lendacky <thomas.lendacky@amd.com>
> CC: John Allen <john.allen@amd.com>
> CC: Herbert Xu <herbert@gondor.apana.org.au>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: Michael Roth <michael.roth@amd.com>
> CC: Luis Chamberlain <mcgrof@kernel.org>
> CC: Russ Weight <russ.weight@linux.dev>
> CC: Danilo Krummrich <dakr@redhat.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: "Rafael J. Wysocki" <rafael@kernel.org>
> CC: Tianfei zhang <tianfei.zhang@intel.com>
> CC: Alexey Kardashevskiy <aik@amd.com>
> 
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
> ---
>  arch/x86/kvm/svm/sev.c       | 18 +++++++++++++++---
>  drivers/crypto/ccp/sev-dev.c | 12 ------------
>  include/linux/psp-sev.h      | 27 ---------------------------
>  3 files changed, 15 insertions(+), 42 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index d0e0152aefb32..cea41b8cdabe4 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -528,21 +528,33 @@ static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
>  	return ret;
>  }
>  
> -static int __sev_issue_cmd(int fd, int id, void *data, int *error)
> +static int sev_check_external_user(int fd)
>  {
>  	struct fd f;
> -	int ret;
> +	int ret = 0;
>  
>  	f = fdget(fd);
>  	if (!fd_file(f))
>  		return -EBADF;
>  
> -	ret = sev_issue_cmd_external_user(fd_file(f), id, data, error);
> +	if (!file_is_sev(fd_file(f)))
> +		ret = -EBADF;
>  
>  	fdput(f);
>  	return ret;
>  }
>  
> +static int __sev_issue_cmd(int fd, int id, void *data, int *error)
> +{
> +	int ret;
> +
> +	ret = sev_check_external_user(fd);
> +	if (ret)
> +		return ret;
> +
> +	return sev_do_cmd(id, data, error);
> +}
> +
>  static int sev_issue_cmd(struct kvm *kvm, int id, void *data, int *error)
>  {
>  	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index f92e6a222da8a..67f6425b7ed07 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -2493,18 +2493,6 @@ bool file_is_sev(struct file *p)
>  }
>  EXPORT_SYMBOL_GPL(file_is_sev);
>  
> -int sev_issue_cmd_external_user(struct file *filep, unsigned int cmd,
> -				void *data, int *error)
> -{
> -	int rc = file_is_sev(filep) ? 0 : -EBADF;
> -
> -	if (rc)
> -		return rc;
> -
> -	return sev_do_cmd(cmd, data, error);
> -}
> -EXPORT_SYMBOL_GPL(sev_issue_cmd_external_user);
> -
>  void sev_pci_init(void)
>  {
>  	struct sev_device *sev = psp_master->sev_data;
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index ed85c0cfcfcbe..b4164d3600702 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -860,30 +860,6 @@ int sev_platform_init(struct sev_platform_init_args *args);
>   */
>  int sev_platform_status(struct sev_user_data_status *status, int *error);
>  
> -/**
> - * sev_issue_cmd_external_user - issue SEV command by other driver with a file
> - * handle.
> - *
> - * This function can be used by other drivers to issue a SEV command on
> - * behalf of userspace. The caller must pass a valid SEV file descriptor
> - * so that we know that it has access to SEV device.
> - *
> - * @filep - SEV device file pointer
> - * @cmd - command to issue
> - * @data - command buffer
> - * @error: SEV command return code
> - *
> - * Returns:
> - * 0 if the SEV successfully processed the command
> - * -%ENODEV    if the SEV device is not available
> - * -%ENOTSUPP  if the SEV does not support SEV
> - * -%ETIMEDOUT if the SEV command timed out
> - * -%EIO       if the SEV returned a non-zero return code
> - * -%EBADF     if the file pointer is bad or does not grant access
> - */
> -int sev_issue_cmd_external_user(struct file *filep, unsigned int id,
> -				void *data, int *error);
> -
>  /**
>   * file_is_sev - returns whether a file pointer is for the SEV device
>   *
> @@ -1043,9 +1019,6 @@ sev_guest_activate(struct sev_data_activate *data, int *error) { return -ENODEV;
>  
>  static inline int sev_guest_df_flush(int *error) { return -ENODEV; }
>  
> -static inline int
> -sev_issue_cmd_external_user(struct file *filep, unsigned int id, void *data, int *error) { return -ENODEV; }
> -
>  static inline bool file_is_sev(struct file *filep) { return false; }
>  
>  static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_PTR(-EINVAL); }