[RFC PATCH] Arm64: introduce __hyp_func_call
From: Arun Chandran <hidden>
Date: 2014-08-27 10:28:34
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
This adds a mechanism to __hyp_stub_vectors to allow a hypercall to call a function at EL2. It is needed for users who want to run a part of code with EL2 permissions. The current usecase is for KVM and kexec. For kexec we need to move the final CPU up to the mode it started in before we branch to the new kernel. If we don't do that * We loose EL2 in the next boot * Arm64 bootwrapper may not be able to put CPUs at the spin-table code. It expects the final jump from kernel to cpu-return-addr to be done in EL2. KVM can use this to set/get VBAR_EL2 Signed-off-by: Arun Chandran <redacted> --- Idea is from "Mark Rutland [off-list ref]" http://lists.infradead.org/pipermail/linux-arm-kernel/2014-August/280026.html --- arch/arm64/include/asm/virt.h | 15 +++++++++++++++ arch/arm64/kernel/hyp-stub.S | 33 +++++++++++++++++++++------------ 2 files changed, 36 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 7a5df52..910a163 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h@@ -34,9 +34,24 @@ */ extern u32 __boot_cpu_mode[2]; +void *__hyp_func_call(u64 __tmp, phys_addr_t func, ...); void __hyp_set_vectors(phys_addr_t phys_vector_base); phys_addr_t __hyp_get_vectors(void); +#define __hyp_set_vectors(__vbase) \ +({ \ + u64 __tmp = 0; \ + __hyp_func_call(__tmp, virt_to_phys(__hyp_set_vectors), __vbase); \ +}) + +#define __hyp_get_vectors() \ +({ \ + u64 __tmp = 0; \ + phys_addr_t ret = (phys_addr_t) __hyp_func_call(__tmp, \ + virt_to_phys(__hyp_get_vectors)); \ + ret; \ +}) + /* Reports the availability of HYP mode */ static inline bool is_hyp_mode_available(void) {
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index a272f33..2144a3f 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S@@ -53,15 +53,14 @@ ENDPROC(__hyp_stub_vectors) .align 11 el1_sync: - mrs x1, esr_el2 - lsr x1, x1, #26 - cmp x1, #0x16 + mrs x0, esr_el2 + lsr x0, x0, #26 + cmp x0, #0x16 b.ne 2f // Not an HVC trap - cbz x0, 1f - msr vbar_el2, x0 // Set vbar_el2 - b 2f -1: mrs x0, vbar_el2 // Return vbar_el2 -2: eret + +1: blr x1 // Jump to the function +2: mov x0, xzr // esr_el2 not readable <= el2 + eret ENDPROC(el1_sync) .macro invalid_vector label
@@ -101,10 +100,20 @@ ENDPROC(\label) */ ENTRY(__hyp_get_vectors) - mov x0, xzr - // fall through -ENTRY(__hyp_set_vectors) - hvc #0 + mrs x0, vbar_el2 // Return vbar_el2 ret ENDPROC(__hyp_get_vectors) + +ENTRY(__hyp_set_vectors) + msr vbar_el2, x2 + ret ENDPROC(__hyp_set_vectors) + +/* Call a function @x1 */ +ENTRY(__hyp_func_call) + /* Save lr here */ + msr elr_el1, x30 + hvc #0 + mrs x30, elr_el1 + ret +ENDPROC(__hyp_func_call)
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1.7.9.5