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author | Takashi Iwai <tiwai@suse.de> | 2019-09-10 14:03:08 +0300 |
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committer | Takashi Iwai <tiwai@suse.de> | 2019-09-10 14:03:08 +0300 |
commit | 7711fb7dac1ab77fd1b4d948f4647a569e4a1ae2 (patch) | |
tree | dd35ad21e0eb13572757dab279ae41f6d953baed /Documentation/virt/kvm/arm/hyp-abi.txt | |
parent | 789492f0c86505e63369907bcb1afdf52dec9366 (diff) | |
parent | bb831786117519fc16dfd3eaa7b84e4f6bbb8d99 (diff) | |
download | linux-7711fb7dac1ab77fd1b4d948f4647a569e4a1ae2.tar.xz |
Merge tag 'asoc-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-next
ASoC: Updates for v5.4
Quite a big update this time around, particularly in the core
where we've had a lot of cleanups from Morimoto-san - there's
not much functional change but quite a bit of modernization
going on. We've also seen a lot of driver work, a lot of it
cleanups but also some particular drivers.
- Lots and lots of cleanups from Morimoto-san and Yue Haibing.
- Lots of cleanups and enhancements to the Freescale, sunxi dnd
Intel rivers.
- Initial Sound Open Firmware suppot for i.MX8.
- Removal of w90x900 and nuc900 drivers as the platforms are
being removed.
- New support for Cirrus Logic CS47L15 and CS47L92, Freescale
i.MX 7ULP and 8MQ, Meson G12A and NXP UDA1334
Diffstat (limited to 'Documentation/virt/kvm/arm/hyp-abi.txt')
-rw-r--r-- | Documentation/virt/kvm/arm/hyp-abi.txt | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/arm/hyp-abi.txt b/Documentation/virt/kvm/arm/hyp-abi.txt new file mode 100644 index 000000000000..a20a0bee268d --- /dev/null +++ b/Documentation/virt/kvm/arm/hyp-abi.txt @@ -0,0 +1,53 @@ +* Internal ABI between the kernel and HYP + +This file documents the interaction between the Linux kernel and the +hypervisor layer when running Linux as a hypervisor (for example +KVM). It doesn't cover the interaction of the kernel with the +hypervisor when running as a guest (under Xen, KVM or any other +hypervisor), or any hypervisor-specific interaction when the kernel is +used as a host. + +On arm and arm64 (without VHE), the kernel doesn't run in hypervisor +mode, but still needs to interact with it, allowing a built-in +hypervisor to be either installed or torn down. + +In order to achieve this, the kernel must be booted at HYP (arm) or +EL2 (arm64), allowing it to install a set of stubs before dropping to +SVC/EL1. These stubs are accessible by using a 'hvc #0' instruction, +and only act on individual CPUs. + +Unless specified otherwise, any built-in hypervisor must implement +these functions (see arch/arm{,64}/include/asm/virt.h): + +* r0/x0 = HVC_SET_VECTORS + r1/x1 = vectors + + Set HVBAR/VBAR_EL2 to 'vectors' to enable a hypervisor. 'vectors' + must be a physical address, and respect the alignment requirements + of the architecture. Only implemented by the initial stubs, not by + Linux hypervisors. + +* r0/x0 = HVC_RESET_VECTORS + + Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials + stubs' exception vector value. This effectively disables an existing + hypervisor. + +* r0/x0 = HVC_SOFT_RESTART + r1/x1 = restart address + x2 = x0's value when entering the next payload (arm64) + x3 = x1's value when entering the next payload (arm64) + x4 = x2's value when entering the next payload (arm64) + + Mask all exceptions, disable the MMU, move the arguments into place + (arm64 only), and jump to the restart address while at HYP/EL2. This + hypercall is not expected to return to its caller. + +Any other value of r0/x0 triggers a hypervisor-specific handling, +which is not documented here. + +The return value of a stub hypercall is held by r0/x0, and is 0 on +success, and HVC_STUB_ERR on error. A stub hypercall is allowed to +clobber any of the caller-saved registers (x0-x18 on arm64, r0-r3 and +ip on arm). It is thus recommended to use a function call to perform +the hypercall. |