Re: [PATCHv5 06/12] x86/boot/compressed: Handle unaccepted memory

Borislav Petkov
2022-05-13T09:01:55Z

+ mroth
- brijesh

On Thu, May 12, 2022 at 10:34:02PM -0700, Dionna Amalie Glaze wrote:
> Kirill, I've been tracking these changes to see if we can handle the
> unaccepted memory type for SEV-SNP, but testing has been an issue. The
> proposed patch in Ovmf to introduce unaccepted memory seems to have
> stalled out last September
> (https://www.mail-archive.com/devel@edk2.groups.io/msg35842.html) and
> is particularly difficult to adapt to SEV-SNP since it doesn't follow
> the TDVF way of initializing all memory. Is there a different
> development I might have missed so that we might test these cases?
> Without the UEFI introducing EFI_UNACCEPTED_MEMORY type, any kernel
> uses are essentially dead code.
>
> Thanks,
> -Dionna
>
> (apologies for repost in text mode)
>
> On Tue, May 10, 2022 at 4:04 AM Borislav Petkov <bp@alien8.de> wrote:
> >
> > On Fri, May 06, 2022 at 06:30:13PM +0300, Kirill A. Shutemov wrote:
> > > I find it harder to follow.
> >
> > If in doubt, always consider using a helper function:
> >
> > ---
> >
> > diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h
> > index 7db2f41b54cd..cf475243b6d5 100644
> > --- a/arch/x86/boot/compressed/efi.h
> > +++ b/arch/x86/boot/compressed/efi.h
> > @@ -32,6 +32,7 @@ typedef struct {
> > } efi_table_hdr_t;
> >
> > #define EFI_CONVENTIONAL_MEMORY 7
> > +#define EFI_UNACCEPTED_MEMORY 15
> >
> > #define EFI_MEMORY_MORE_RELIABLE \
> > ((u64)0x0000000000010000ULL) /* higher reliability */
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 28b91df9d31e..39bb4c319dfc 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -671,6 +671,23 @@ static bool process_mem_region(struct mem_vector *region,
> > }
> >
> > #ifdef CONFIG_EFI
> > +
> > +/*
> > + * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if supported) are guaranteed
> > + * to be free.
> > + */
> > +static inline bool memory_type_is_free(efi_memory_desc_t *md)
> > +{
> > + if (md->type == EFI_CONVENTIONAL_MEMORY)
> > + return true;
> > +
> > + if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
> > + if (md->type == EFI_UNACCEPTED_MEMORY)
> > + return true;
> > +
> > + return false;
> > +}
> > +
> > /*
> > * Returns true if we processed the EFI memmap, which we prefer over the E820
> > * table if it is available.
> > @@ -723,21 +740,9 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
> > * free memory and thus available to place the kernel image into,
> > * but in practice there's firmware where using that memory leads
> > * to crashes.
> > - *
> > - * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if
> > - * supported) are guaranteed to be free.
> > */
> > -
> > - switch (md->type) {
> > - case EFI_CONVENTIONAL_MEMORY:
> > - break;
> > - case EFI_UNACCEPTED_MEMORY:
> > - if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
> > - break;
> > + if (!memory_type_is_free(md))
> > continue;
> > - default:
> > - continue;
> > - }
> >
> > if (efi_soft_reserve_enabled() &&
> > (md->attribute & EFI_MEMORY_SP))
> > --
> > Regards/Gruss,
> > Boris.
> >
> > https://people.kernel.org/tglx/notes-about-netiquette
>
>
>
> --
> -Dionna Glaze, PhD (she/her)
>

--
Regards/Gruss,
Boris.

SUSE Software Solutions Germany GmbH, GF: Ivo Totev, HRB 36809, AG Nürnberg