On Fri, May 15, 2026 at 12:26:32PM +0530, Aswin Murugan wrote: > Add support for exiting Gunyah hypervisor and switching to EL2 during > early boot. This is required for platforms that boot U-Boot in a > hypervisor guest environment where U-Boot needs to run at EL2 to > enable other hypervisors like KVM. > > The switch is performed via TrustZone SMC call before EL register > configuration in start.S. The implementation: > > - Checks current exception level and only executes at EL1 > - Uses TrustZone SMC to exit Gunyah and transition to EL2 > - Integrates with existing boot0.h infrastructure > > A new Kconfig option CONFIG_QCOM_EL2_GUNYAH_EXIT_SUPPORT enables this > functionality. > > Signed-off-by: Aswin Murugan <[email protected]> > --- > Change in v2: > - EL2 switch is made at early stage instead of doing at the very last stage in > the previous version > - This change is based on the patch [1] > > [1] https://lore.kernel.org/all/[email protected]/ > > Link to v1: > https://lore.kernel.org/u-boot/[email protected]/ > --- > arch/arm/mach-snapdragon/Kconfig | 7 ++++ > arch/arm/mach-snapdragon/include/mach/boot0.h | 3 ++ > .../include/mach/gunyah_exit_boot0.h | 36 +++++++++++++++++++ > 3 files changed, 46 insertions(+) > create mode 100644 arch/arm/mach-snapdragon/include/mach/gunyah_exit_boot0.h > > diff --git a/arch/arm/mach-snapdragon/Kconfig > b/arch/arm/mach-snapdragon/Kconfig > index f863daf6bb9..931d25c1023 100644 > --- a/arch/arm/mach-snapdragon/Kconfig > +++ b/arch/arm/mach-snapdragon/Kconfig > @@ -56,6 +56,13 @@ config BOOT0_MSM8916_PSCI_WORKAROUND > help > Select this if you are building U-Boot proper for an msm8916 board > that > uses the buggy PSCI implementation. > + > +config QCOM_EL2_GUNYAH_EXIT_SUPPORT > + bool "Enable early EL2 switch by exiting Gunyah" > + help > + Exit Gunyah hypervisor and switch to EL2 during early boot. This must > + happen before EL register configuration in start.S so that U-Boot can > + run properly at EL2. > endchoice > > endif > diff --git a/arch/arm/mach-snapdragon/include/mach/boot0.h > b/arch/arm/mach-snapdragon/include/mach/boot0.h > index b3c76d6d97d..032a9fbdb12 100644 > --- a/arch/arm/mach-snapdragon/include/mach/boot0.h > +++ b/arch/arm/mach-snapdragon/include/mach/boot0.h > @@ -1,9 +1,12 @@ > /* SPDX-License-Identifier: GPL-2.0+ */ > + > #if defined(CONFIG_SPL_BUILD) > b reset > #else > #if defined(CONFIG_BOOT0_MSM8916_PSCI_WORKAROUND) > #include "msm8916_boot0.h" > +#elif defined(CONFIG_QCOM_EL2_GUNYAH_EXIT_SUPPORT) > +#include "gunyah_exit_boot0.h" > #else > b reset > #endif > diff --git a/arch/arm/mach-snapdragon/include/mach/gunyah_exit_boot0.h > b/arch/arm/mach-snapdragon/include/mach/gunyah_exit_boot0.h > new file mode 100644 > index 00000000000..f69678018ea > --- /dev/null > +++ b/arch/arm/mach-snapdragon/include/mach/gunyah_exit_boot0.h > @@ -0,0 +1,36 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * Early Gunyah Hypervisor Exit > + * > + * Exit Gunyah hypervisor and switch to EL2 during early boot. This must > + * happen before EL register configuration in start.S so that U-Boot can > + * run properly at EL2. > + */ > + > +#include <linux/arm-smccc.h> > + > +/* TrustZone SMC IDs for hypervisor configuration */ > +#define TZ_EL2_SWITCH_SMC_ID 0x02000121 > +#define TZ_EL2_SWITCH_PARAM_ID 0x00000023 > +#define TZ_EL2_SWITCH_PARAM2_EXIT_GUNYAH 0x1 > + > + /* Save FDT address before we modify x0 */ > + mov x9, x0 > + > + /* Only perform hypervisor switch if we're at EL1 */ > + mrs x0, CurrentEL > + cmp x0, #(1 << 2) > + bne 1f
Above logic is somewhat broken when U-Boot enters in EL2 by default, see corresponding fix here [1]. Please fold in this fix for v3. [1] https://github.com/qualcomm-linux/u-boot/pull/64 -Sumit > + > + /* Switch to EL2 (exit Gunyah) */ > + ldr w0, =TZ_EL2_SWITCH_SMC_ID > + ldr w1, =TZ_EL2_SWITCH_PARAM_ID > + mov w2, wzr > + mov w3, wzr > + ldr w4, =TZ_EL2_SWITCH_PARAM2_EXIT_GUNYAH > + smc #0 > + > + /* Restore FDT address */ > + mov x0, x9 > +1: > + b reset > -- > 2.34.1 >
