[PATCH 13/20] ARM: KVM: Implement HVC_RESET_VECTORS stub hypercall

In order to restore HYP mode to its original condition, KVM currently
implements __kvm_hyp_reset(). As we're moving towards a hyp-stub
defined API, it becomes necessary to implement HVC_RESET_VECTORS.

This patch adds the HVC_RESET_VECTORS hypercall to the KVM init
code, which so far lacked any form of hypercall support.

Signed-off-by: Marc Zyngier <redacted>
---
 arch/arm/kernel/hyp-stub.S |  1 +
 arch/arm/kvm/init.S        | 37 +++++++++++++++++++++++++++++++------
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
index cf6d801f89e8..171a09cdf6b3 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S

@@ -280,6 +280,7 @@ ENDPROC(__hyp_reset_vectors)

 .align 5
 __hyp_stub_vectors:
+.global __hyp_stub_vectors

 __hyp_stub_reset:      W(b)    .
 __hyp_stub_und:                W(b)    .
 __hyp_stub_svc:                W(b)    .

diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index bf89c919efc1..b0138118fac4 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S

@@ -23,6 +23,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/virt.h>

 /********************************************************************
  * Hypervisor initialization

@@ -39,6 +40,10 @@
  * - Setup the page tables
  * - Enable the MMU
  * - Profit! (or eret, if you only care about the code).
+ *
+ * Another possibility is to get a HYP stub hypercall.
+ * We discriminate between the two by checking if r0 contains a value
+ * that is less than HVC_STUB_HCALL_NR.
  */

        .text

@@ -58,6 +63,10 @@ __kvm_hyp_init:
        W(b)    .

 __do_hyp_init:
+       @ Check for a stub hypercall
+       cmp     r0, #HVC_STUB_HCALL_NR
+       blo     __kvm_handle_stub_hvc
+
        @ Set stack pointer
        mov     sp, r0

@@ -112,22 +121,38 @@ __do_hyp_init:

        eret

-       @ r0 : stub vectors address
+ENTRY(__kvm_handle_stub_hvc)
+       cmp     r0, #HVC_RESET_VECTORS
+       bne     1f
 ENTRY(__kvm_hyp_reset)
        /* We're now in idmap, disable MMU */
        mrc     p15, 4, r1, c1, c0, 0   @ HSCTLR
-       ldr     r2, =(HSCTLR_M | HSCTLR_A | HSCTLR_C | HSCTLR_I)
-       bic     r1, r1, r2
+       ldr     r0, =(HSCTLR_M | HSCTLR_A | HSCTLR_C | HSCTLR_I)
+       bic     r1, r1, r0
        mcr     p15, 4, r1, c1, c0, 0   @ HSCTLR

-       /* Install stub vectors */
-       mcr     p15, 4, r0, c12, c0, 0  @ HVBAR
-       isb
+       /*
+        * Install stub vectors. We cannot use 'adr' to get to the
+        * stub vectors, hence having to play the VA->PA game.
+        */
+       adr     r0, .L__va2pa   @ PA
+       ldr     r1, [r0]        @ VA
+       sub     r0, r0, r1      @ PA - VA
+       ldr     r1, =__hyp_stub_vectors
+       add     r1, r1, r0
+       mcr     p15, 4, r1, c12, c0, 0  @ HVBAR
+       b       exit
+
+1:     mov     r0, #-1

+exit:
        eret
+ENDPROC(__kvm_handle_stub_hvc)
 ENDPROC(__kvm_hyp_reset)

        .ltorg
+.L__va2pa:
+       .word   .

        .globl __kvm_hyp_init_end
 __kvm_hyp_init_end:
--

2.11.0


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