Re: [PATCH] arm64: efi: Force the use of SetVirtualAddressMap() on Altra machines

Alexandru Elisei
2022-11-10T15:35:09Z

Hi,

On Thu, Nov 10, 2022 at 03:45:03PM +0100, Ard Biesheuvel wrote:
> On Thu, 10 Nov 2022 at 15:37, Alexandru Elisei <alexandru.elisei@arm.com> wrote:
> >
> > Hi,
> >
> > On Thu, Nov 10, 2022 at 10:49:51AM +0100, Ard Biesheuvel wrote:
> > > Ampere Altra machines are reported to misbehave when the SetTime() EFI
> > > runtime service is called after ExitBootServices() but before calling
> > > SetVirtualAddressMap(). Given that the latter is horrid, pointless and
> > > explicitly documented as optional by the EFI spec, we no longer invoke
> > > it at boot if the configured size of the VA space guarantees that the
> > > EFI runtime memory regions can remain mapped 1:1 like they are at boot
> > > time.
> > >
> > > This means that SetTime() calls on Ampere Altra machines issued by the
> > > rtc-efi driver now trigger a synchronous exception during boot. We can
> > > now recover from those without bringing down the system entirely, due to
> > > commit 23715a26c8d81291 ("arm64: efi: Recover from synchronous
> > > exceptions occurring in firmware"). However, it would be better to avoid
> > > this completely, given that the firmware appears to remain in a funny
> > > state after this.
> > >
> > > So attempt to identify these machines based on the 'family' field in the
> > > type #1 SMBIOS record, and call SetVirtualAddressMap() unconditionally
> > > in that case.
> >
> > This works for my machine. Tested with this patch on top of the patch [1] that
> > disables only the misbehaving services, not runtime services altogether (can
> > test other configurations, if you feel it's necessary):
> >
> > Tested-by: Alexandru Elisei <alexandru.elisei@gmail.com>
> >
>
> Thanks.
>
> I take it this means that efibootmgr now works as it should?

Yes, tested GetVariable() (# efibootmgr) and SetVariable() (# efibootmgr -t
30). Also tested this patch on top of v6.1-rc4, same results.

Thanks,
Alex

>
> > [1] https://lore.kernel.org/all/20221108151509.2250968-1-ardb@kernel.org/
> >
>
> I probably won't merge both of these as fixes, but if this patch on
> top of [1] improves the situation and makes EFI variables work again,
> this patch by itself should be sufficient in the short term.
>
>
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > > drivers/firmware/efi/libstub/Makefile | 2 +-
> > > drivers/firmware/efi/libstub/arm64-stub.c | 17 ++++++-
> > > drivers/firmware/efi/libstub/efistub.h | 28 ++++++++++
> > > drivers/firmware/efi/libstub/smbios.c | 62 +++++++++++++++++++++++
> > > include/linux/efi.h | 1 +
> > > 5 files changed, 108 insertions(+), 2 deletions(-)
> > > create mode 100644 drivers/firmware/efi/libstub/smbios.c
> > >
> > > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> > > index b1601aad7e1a8d66..ef5045a53ce09653 100644
> > > --- a/drivers/firmware/efi/libstub/Makefile
> > > +++ b/drivers/firmware/efi/libstub/Makefile
> > > @@ -82,7 +82,7 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
> > > lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o
> > >
> > > lib-$(CONFIG_ARM) += arm32-stub.o
> > > -lib-$(CONFIG_ARM64) += arm64-stub.o
> > > +lib-$(CONFIG_ARM64) += arm64-stub.o smbios.o
> > > lib-$(CONFIG_X86) += x86-stub.o
> > > lib-$(CONFIG_RISCV) += riscv-stub.o
> > > lib-$(CONFIG_LOONGARCH) += loongarch-stub.o
> > > diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> > > index 259e4b852d63276d..f9de5217ea65ed93 100644
> > > --- a/drivers/firmware/efi/libstub/arm64-stub.c
> > > +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> > > @@ -15,6 +15,21 @@
> > >
> > > #include "efistub.h"
> > >
> > > +static bool system_needs_vamap(void)
> > > +{
> > > + const u8 *type1_family = efi_get_smbios_string(1, family);
> > > +
> > > + /*
> > > + * Ampere Altra machines crash in SetTime() if SetVirtualAddressMap()
> > > + * has not been called prior.
> > > + */
> > > + if (!type1_family || strcmp(type1_family, "Altra"))
> > > + return false;
> > > +
> > > + efi_warn("Working around broken SetVirtualAddressMap()\n");
> > > + return true;
> > > +}
> > > +
> > > efi_status_t check_platform_features(void)
> > > {
> > > u64 tg;
> > > @@ -24,7 +39,7 @@ efi_status_t check_platform_features(void)
> > > * UEFI runtime regions 1:1 and so calling SetVirtualAddressMap() is
> > > * unnecessary.
> > > */
> > > - if (VA_BITS_MIN >= 48)
> > > + if (VA_BITS_MIN >= 48 && !system_needs_vamap())
> > > efi_novamap = true;
> > >
> > > /* UEFI mandates support for 4 KB granularity, no need to check */
> > > diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> > > index a30fb5d8ef05ae9c..eb03d5a9aac88e84 100644
> > > --- a/drivers/firmware/efi/libstub/efistub.h
> > > +++ b/drivers/firmware/efi/libstub/efistub.h
> > > @@ -975,4 +975,32 @@ efi_enable_reset_attack_mitigation(void) { }
> > >
> > > void efi_retrieve_tpm2_eventlog(void);
> > >
> > > +struct efi_smbios_record {
> > > + u8 type;
> > > + u8 length;
> > > + u16 handle;
> > > +};
> > > +
> > > +struct efi_smbios_type1_record {
> > > + struct efi_smbios_record header;
> > > +
> > > + u8 manufacturer;
> > > + u8 product_name;
> > > + u8 version;
> > > + u8 serial_number;
> > > + efi_guid_t uuid;
> > > + u8 wakeup_type;
> > > + u8 sku_number;
> > > + u8 family;
> > > +};
> > > +
> > > +#define efi_get_smbios_string(__type, __name) ({ \
> > > + int size = sizeof(struct efi_smbios_type ## __type ## _record); \
> > > + int off = offsetof(struct efi_smbios_type ## __type ## _record, \
> > > + __name); \
> > > + __efi_get_smbios_string(__type, off, size); \
> > > +})
> > > +
> > > +const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize);
> > > +
> > > #endif
> > > diff --git a/drivers/firmware/efi/libstub/smbios.c b/drivers/firmware/efi/libstub/smbios.c
> > > new file mode 100644
> > > index 0000000000000000..0b7fbd85cc2f6b4b
> > > --- /dev/null
> > > +++ b/drivers/firmware/efi/libstub/smbios.c
> > > @@ -0,0 +1,62 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +// Copyright 2022 Google LLC
> > > +// Author: Ard Biesheuvel <ardb@google.com>
> > > +
> > > +#include <linux/efi.h>
> > > +
> > > +#include "efistub.h"
> > > +
> > > +typedef union efi_smbios_protocol efi_smbios_protocol_t;
> > > +
> > > +union efi_smbios_protocol {
> > > + struct {
> > > + efi_status_t (__efiapi *add)(efi_smbios_protocol_t *,
> > > + efi_handle_t, u16 *,
> > > + struct efi_smbios_record *);
> > > + efi_status_t (__efiapi *update_string)(efi_smbios_protocol_t *,
> > > + u16 *, unsigned long *,
> > > + u8 *);
> > > + efi_status_t (__efiapi *remove)(efi_smbios_protocol_t *, u16);
> > > + efi_status_t (__efiapi *get_next)(efi_smbios_protocol_t *,
> > > + u16 *, u8 *,
> > > + struct efi_smbios_record **,
> > > + efi_handle_t *);
> > > +
> > > + u8 major_version;
> > > + u8 minor_version;
> > > + };
> > > + struct {
> > > + u32 add;
> > > + u32 update_string;
> > > + u32 remove;
> > > + u32 get_next;
> > > +
> > > + u8 major_version;
> > > + u8 minor_version;
> > > + } mixed_mode;
> > > +};
> > > +
> > > +const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize)
> > > +{
> > > + struct efi_smbios_record *record;
> > > + efi_smbios_protocol_t *smbios;
> > > + efi_status_t status;
> > > + u16 handle = 0xfffe;
> > > + const u8 *strtable;
> > > +
> > > + status = efi_bs_call(locate_protocol, &EFI_SMBIOS_PROTOCOL_GUID, NULL,
> > > + (void **)&smbios) ?:
> > > + efi_call_proto(smbios, get_next, &handle, &type, &record, NULL);
> > > + if (status != EFI_SUCCESS)
> > > + return NULL;
> > > +
> > > + strtable = (u8 *)record + recsize;
> > > + for (int i = 1; i < ((u8 *)record)[offset]; i++) {
> > > + int len = strlen(strtable);
> > > +
> > > + if (!len)
> > > + return NULL;
> > > + strtable += len + 1;
> > > + }
> > > + return strtable;
> > > +}
> > > diff --git a/include/linux/efi.h b/include/linux/efi.h
> > > index 61b252386d61cc4d..cf88dda630649f87 100644
> > > --- a/include/linux/efi.h
> > > +++ b/include/linux/efi.h
> > > @@ -389,6 +389,7 @@ void efi_native_runtime_setup(void);
> > > #define EFI_LOAD_FILE2_PROTOCOL_GUID EFI_GUID(0x4006c0c1, 0xfcb3, 0x403e, 0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 0x6d)
> > > #define EFI_RT_PROPERTIES_TABLE_GUID EFI_GUID(0xeb66918a, 0x7eef, 0x402a, 0x84, 0x2e, 0x93, 0x1d, 0x21, 0xc3, 0x8a, 0xe9)
> > > #define EFI_DXE_SERVICES_TABLE_GUID EFI_GUID(0x05ad34ba, 0x6f02, 0x4214, 0x95, 0x2e, 0x4d, 0xa0, 0x39, 0x8e, 0x2b, 0xb9)
> > > +#define EFI_SMBIOS_PROTOCOL_GUID EFI_GUID(0x03583ff6, 0xcb36, 0x4940, 0x94, 0x7e, 0xb9, 0xb3, 0x9f, 0x4a, 0xfa, 0xf7)
> > >
> > > #define EFI_IMAGE_SECURITY_DATABASE_GUID EFI_GUID(0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f)
> > > #define EFI_SHIM_LOCK_GUID EFI_GUID(0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23)
> > > --
> > > 2.35.1
> > >