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SubjectRe: [PATCH] x86/efi: Don't require non-blocking EFI callbacks
On Thu, 26 Sep 2019 at 16:12, Ross Lagerwall <ross.lagerwall@citrix.com> wrote:
>
> If a backend does not implement non-blocking EFI operations, it implies
> that the normal operations are non-blocking.

Is that documented anywhere?

> Instead of crashing
> dereferencing a NULL pointer, fallback to the normal operations since it
> is safe to do so.
>

I agree that crashing is never the right thing to do, but I wonder
whether we shouldn't just bail instead. If the provided default
operation is non-blocking, the platform can populate the function
pointer with a reference to the default implementation.


> Fixes: 5a58bc1b1edc ("efi/x86: Use non-blocking SetVariable() for efi_delete_dummy_variable()")
> Fixes: ca0e30dcaa53 ("efi: Add nonblocking option to efi_query_variable_store()")
> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
> ---
> arch/x86/platform/efi/quirks.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index 3b9fd679cea9..4167f5e8f3e8 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -106,11 +106,13 @@ early_param("efi_no_storage_paranoia", setup_storage_paranoia);
> */
> void efi_delete_dummy_variable(void)
> {
> - efi.set_variable_nonblocking((efi_char16_t *)efi_dummy_name,
> - &EFI_DUMMY_GUID,
> - EFI_VARIABLE_NON_VOLATILE |
> - EFI_VARIABLE_BOOTSERVICE_ACCESS |
> - EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL);
> + efi_set_variable_t *set_variable = efi.set_variable_nonblocking ?:
> + efi.set_variable;
> +
> + set_variable((efi_char16_t *)efi_dummy_name, &EFI_DUMMY_GUID,
> + EFI_VARIABLE_NON_VOLATILE |
> + EFI_VARIABLE_BOOTSERVICE_ACCESS |
> + EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL);
> }
>
> /*
> @@ -127,10 +129,12 @@ query_variable_store_nonblocking(u32 attributes, unsigned long size)
> {
> efi_status_t status;
> u64 storage_size, remaining_size, max_size;
> + efi_query_variable_info_t *query_variable_info =
> + efi.query_variable_info_nonblocking ?:
> + efi.query_variable_info;
>
> - status = efi.query_variable_info_nonblocking(attributes, &storage_size,
> - &remaining_size,
> - &max_size);
> + status = query_variable_info(attributes, &storage_size,
> + &remaining_size, &max_size);
> if (status != EFI_SUCCESS)
> return status;
>
> --
> 2.21.0
>

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