On Tue, 17 Jan 2023 at 13:29, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Thu, Jan 12, 2023 at 2:33 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >
> > The ACPI PRM address space handler calls efi_call_virt_pointer() to
> > execute PRM firmware code, but doing so is only permitted when the EFI
> > runtime environment is available. Otherwise, such calls are guaranteed
> > to result in a crash, and must therefore be avoided.
> >
> > Given that the EFI runtime services may become unavailable after a crash
> > occurring in the firmware, we need to check this each time the PRM
> > address space handler is invoked. If the EFI runtime services were not
> > available at registration time to being with, don't install the address
> > space handler at all.
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> > Cc: Len Brown <lenb@xxxxxxxxxx>
> > Cc: linux-acpi@xxxxxxxxxxxxxxx
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > ---
> > v2: check both at registration and at invocation time
> >
> > drivers/acpi/prmt.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
> > index 998101cf16e47145..3d4c4620f9f95309 100644
> > --- a/drivers/acpi/prmt.c
> > +++ b/drivers/acpi/prmt.c
> > @@ -236,6 +236,11 @@ static acpi_status acpi_platformrt_space_handler(u32 function,
> > efi_status_t status;
> > struct prm_context_buffer context;
> >
> > + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> > + pr_err_ratelimited("PRM: EFI runtime services no longer available\n");
> > + return AE_NO_HANDLER;
>
> This error code is only used in GPE handling ATM.
>
> The one that actually causes ACPICA to log a "no handler" error (in
> acpi_ex_access_region()) is AE_NOT_EXIST. Should it be used here?
>
Not sure. Any error value is returned to the caller, the only
difference is that AE_NOT_EXIST and AE_NOT_IMPLEMENTED trigger the
non-ratelimited logging machinery.
Given that neither value seems appropriate (the region is implemented
and it has a handler), and we already emit a rate limited error
message, I think AE_NOT_EXIST is not the right choice.
>
> > + }
> > +
> > /*
> > * The returned acpi_status will always be AE_OK. Error values will be
> > * saved in the first byte of the PRM message buffer to be used by ASL.
> > @@ -325,6 +330,11 @@ void __init init_prmt(void)
> >
> > pr_info("PRM: found %u modules\n", mc);
> >
> > + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> > + pr_err("PRM: EFI runtime services unavailable\n");
> > + return;
> > + }
> > +
> > status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
> > ACPI_ADR_SPACE_PLATFORM_RT,
> > &acpi_platformrt_space_handler,
> > --
> > 2.39.0
> >
