KVM: ARM: Hypervisor initialization

Sets up KVM code to handle all exceptions taken to Hyp mode.

When the kernel is booted in Hyp mode, calling an hvc instruction with r0
pointing to the new vectors, the HVBAR is changed to the the vector pointers.
This allows subsystems (like KVM here) to execute code in Hyp-mode with the
MMU disabled.

We initialize other Hyp-mode registers and enables the MMU for Hyp-mode from
the id-mapped hyp initialization code. Afterwards, the HVBAR is changed to
point to KVM Hyp vectors used to catch guest faults and to switch to Hyp mode
to perform a world-switch into a KVM guest.

Also provides memory mapping code to map required code pages, data structures,
and I/O regions  accessed in Hyp mode at the same virtual address as the host
kernel virtual addresses, but which conforms to the architectural requirements
for translations in Hyp mode. This interface is added in arch/arm/kvm/arm_mmu.c
and comprises:
 - create_hyp_mappings(from, to);
 - create_hyp_io_mappings(from, to, phys_addr);
 - free_hyp_pmds();

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

1 files changed, 95 insertions, 0 deletions

diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index 1dc8926e26d2..9f37a79b880b 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S
@@ -15,5 +15,100 @@
  * along with this program; if not, write to the Free Software
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
+
+#include <linux/linkage.h>
+#include <asm/unified.h>
 #include <asm/asm-offsets.h>
 #include <asm/kvm_asm.h>
+#include <asm/kvm_arm.h>
+
+/********************************************************************
+ * Hypervisor initialization
+ *   - should be called with:
+ *       r0,r1 = Hypervisor pgd pointer
+ *       r2 = top of Hyp stack (kernel VA)
+ *       r3 = pointer to hyp vectors
+ */
+
+	.text
+	.pushsection    .hyp.idmap.text,"ax"
+	.align 5
+__kvm_hyp_init:
+	.globl __kvm_hyp_init
+
+	@ Hyp-mode exception vector
+	W(b)	.
+	W(b)	.
+	W(b)	.
+	W(b)	.
+	W(b)	.
+	W(b)	__do_hyp_init
+	W(b)	.
+	W(b)	.
+
+__do_hyp_init:
+	@ Set the HTTBR to point to the hypervisor PGD pointer passed
+	mcrr	p15, 4, r0, r1, c2
+
+	@ Set the HTCR and VTCR to the same shareability and cacheability
+	@ settings as the non-secure TTBCR and with T0SZ == 0.
+	mrc	p15, 4, r0, c2, c0, 2	@ HTCR
+	ldr	r12, =HTCR_MASK
+	bic	r0, r0, r12
+	mrc	p15, 0, r1, c2, c0, 2	@ TTBCR
+	and	r1, r1, #(HTCR_MASK & ~TTBCR_T0SZ)
+	orr	r0, r0, r1
+	mcr	p15, 4, r0, c2, c0, 2	@ HTCR
+
+	mrc	p15, 4, r1, c2, c1, 2	@ VTCR
+	ldr	r12, =VTCR_MASK
+	bic	r1, r1, r12
+	bic	r0, r0, #(~VTCR_HTCR_SH)	@ clear non-reusable HTCR bits
+	orr	r1, r0, r1
+	orr	r1, r1, #(KVM_VTCR_SL0 | KVM_VTCR_T0SZ | KVM_VTCR_S)
+	mcr	p15, 4, r1, c2, c1, 2	@ VTCR
+
+	@ Use the same memory attributes for hyp. accesses as the kernel
+	@ (copy MAIRx ro HMAIRx).
+	mrc	p15, 0, r0, c10, c2, 0
+	mcr	p15, 4, r0, c10, c2, 0
+	mrc	p15, 0, r0, c10, c2, 1
+	mcr	p15, 4, r0, c10, c2, 1
+
+	@ Set the HSCTLR to:
+	@  - ARM/THUMB exceptions: Kernel config (Thumb-2 kernel)
+	@  - Endianness: Kernel config
+	@  - Fast Interrupt Features: Kernel config
+	@  - Write permission implies XN: disabled
+	@  - Instruction cache: enabled
+	@  - Data/Unified cache: enabled
+	@  - Memory alignment checks: enabled
+	@  - MMU: enabled (this code must be run from an identity mapping)
+	mrc	p15, 4, r0, c1, c0, 0	@ HSCR
+	ldr	r12, =HSCTLR_MASK
+	bic	r0, r0, r12
+	mrc	p15, 0, r1, c1, c0, 0	@ SCTLR
+	ldr	r12, =(HSCTLR_EE | HSCTLR_FI | HSCTLR_I | HSCTLR_C)
+	and	r1, r1, r12
+ ARM(	ldr	r12, =(HSCTLR_M | HSCTLR_A)			)
+ THUMB(	ldr	r12, =(HSCTLR_M | HSCTLR_A | HSCTLR_TE)		)
+	orr	r1, r1, r12
+	orr	r0, r0, r1
+	isb
+	mcr	p15, 4, r0, c1, c0, 0	@ HSCR
+	isb
+
+	@ Set stack pointer and return to the kernel
+	mov	sp, r2
+
+	@ Set HVBAR to point to the HYP vectors
+	mcr	p15, 4, r3, c12, c0, 0	@ HVBAR
+
+	eret
+
+	.ltorg
+
+	.globl __kvm_hyp_init_end
+__kvm_hyp_init_end:
+
+	.popsection