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arm64: Provide an 'upgrade to VHE' stub hypercall

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As we are about to change the way a VHE system boots, let's
provide the core helper, in the form of a stub hypercall that
enables VHE and replicates the full EL1 context at EL2, thanks
to EL1 and VHE-EL2 being extremely similar.

On exception return, the kernel carries on at EL2. Fancy!

Nothing calls this new hypercall yet, so no functional change.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: David Brazdil <dbrazdil@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210208095732.3267263-5-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2021-02-08 09:57:13 +00:00 committed by Will Deacon
parent 8cc8a32415
commit f359182291
2 changed files with 80 additions and 3 deletions
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7
arch/arm64/include/asm/virt.h
View File

@ -35,8 +35,13 @@
*/
#define HVC_RESET_VECTORS 2
/*
* HVC_VHE_RESTART - Upgrade the CPU from EL1 to EL2, if possible
*/
#define HVC_VHE_RESTART 3
/* Max number of HYP stub hypercalls */
#define HVC_STUB_HCALL_NR 3
#define HVC_STUB_HCALL_NR 4
/* Error returned when an invalid stub number is passed into x0 */
#define HVC_STUB_ERR 0xbadca11

76
arch/arm64/kernel/hyp-stub.S
View File

@ -8,9 +8,9 @@
#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/irqchip/arm-gic-v3.h>
#include <asm/assembler.h>
#include <asm/el2_setup.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_asm.h>
#include <asm/ptrace.h>
@ -47,10 +47,13 @@ SYM_CODE_END(__hyp_stub_vectors)
SYM_CODE_START_LOCAL(el1_sync)
cmp x0, #HVC_SET_VECTORS
b.ne 2f
b.ne 1f
msr vbar_el2, x1
b 9f
1: cmp x0, #HVC_VHE_RESTART
b.eq mutate_to_vhe
2: cmp x0, #HVC_SOFT_RESTART
b.ne 3f
mov x0, x2
@ -70,6 +73,75 @@ SYM_CODE_START_LOCAL(el1_sync)
eret
SYM_CODE_END(el1_sync)
// nVHE? No way! Give me the real thing!
SYM_CODE_START_LOCAL(mutate_to_vhe)
// Be prepared to fail
mov_q x0, HVC_STUB_ERR
// Sanity check: MMU *must* be off
mrs x1, sctlr_el2
tbnz x1, #0, 1f
// Needs to be VHE capable, obviously
mrs x1, id_aa64mmfr1_el1
ubfx x1, x1, #ID_AA64MMFR1_VHE_SHIFT, #4
cbz x1, 1f
// Engage the VHE magic!
mov_q x0, HCR_HOST_VHE_FLAGS
msr hcr_el2, x0
isb
// Doesn't do much on VHE, but still, worth a shot
init_el2_state vhe
// Use the EL1 allocated stack, per-cpu offset
mrs x0, sp_el1
mov sp, x0
mrs x0, tpidr_el1
msr tpidr_el2, x0
// FP configuration, vectors
mrs_s x0, SYS_CPACR_EL12
msr cpacr_el1, x0
mrs_s x0, SYS_VBAR_EL12
msr vbar_el1, x0
// Transfer the MM state from EL1 to EL2
mrs_s x0, SYS_TCR_EL12
msr tcr_el1, x0
mrs_s x0, SYS_TTBR0_EL12
msr ttbr0_el1, x0
mrs_s x0, SYS_TTBR1_EL12
msr ttbr1_el1, x0
mrs_s x0, SYS_MAIR_EL12
msr mair_el1, x0
isb
// Invalidate TLBs before enabling the MMU
tlbi vmalle1
dsb nsh
// Enable the EL2 S1 MMU, as set up from EL1
mrs_s x0, SYS_SCTLR_EL12
set_sctlr_el1 x0
// Disable the EL1 S1 MMU for a good measure
mov_q x0, INIT_SCTLR_EL1_MMU_OFF
msr_s SYS_SCTLR_EL12, x0
// Hack the exception return to stay at EL2
mrs x0, spsr_el1
and x0, x0, #~PSR_MODE_MASK
mov x1, #PSR_MODE_EL2h
orr x0, x0, x1
msr spsr_el1, x0
mov x0, xzr
1: eret
SYM_CODE_END(mutate_to_vhe)
.macro invalid_vector label
SYM_CODE_START_LOCAL(\label)
b \label