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5a677ce044
Our HYP init code suffers from two major design issues: - it cannot support CPU hotplug, as we tear down the idmap very early - it cannot perform a TLB invalidation when switching from init to runtime mappings, as pages are manipulated from PL1 exclusively The hotplug problem mandates that we keep two sets of page tables (boot and runtime). The TLB problem mandates that we're able to transition from one PGD to another while in HYP, invalidating the TLBs in the process. To be able to do this, we need to share a page between the two page tables. A page that will have the same VA in both configurations. All we need is a VA that has the following properties: - This VA can't be used to represent a kernel mapping. - This VA will not conflict with the physical address of the kernel text The vectors page seems to satisfy this requirement: - The kernel never maps anything else there - The kernel text being copied at the beginning of the physical memory, it is unlikely to use the last 64kB (I doubt we'll ever support KVM on a system with something like 4MB of RAM, but patches are very welcome). Let's call this VA the trampoline VA. Now, we map our init page at 3 locations: - idmap in the boot pgd - trampoline VA in the boot pgd - trampoline VA in the runtime pgd The init scenario is now the following: - We jump in HYP with four parameters: boot HYP pgd, runtime HYP pgd, runtime stack, runtime vectors - Enable the MMU with the boot pgd - Jump to a target into the trampoline page (remember, this is the same physical page!) - Now switch to the runtime pgd (same VA, and still the same physical page!) - Invalidate TLBs - Set stack and vectors - Profit! (or eret, if you only care about the code). Note that we keep the boot mapping permanently (it is not strictly an idmap anymore) to allow for CPU hotplug in later patches. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>
154 lines
4.3 KiB
ArmAsm
154 lines
4.3 KiB
ArmAsm
/*
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* Copyright (C) 2012 - Virtual Open Systems and Columbia University
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* Author: Christoffer Dall <c.dall@virtualopensystems.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License, version 2, as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <linux/linkage.h>
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#include <asm/unified.h>
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#include <asm/asm-offsets.h>
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#include <asm/kvm_asm.h>
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#include <asm/kvm_arm.h>
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#include <asm/kvm_mmu.h>
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/********************************************************************
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* Hypervisor initialization
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* - should be called with:
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* r0 = top of Hyp stack (kernel VA)
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* r1 = pointer to hyp vectors
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* r2,r3 = Hypervisor pgd pointer
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*
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* The init scenario is:
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* - We jump in HYP with four parameters: boot HYP pgd, runtime HYP pgd,
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* runtime stack, runtime vectors
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* - Enable the MMU with the boot pgd
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* - Jump to a target into the trampoline page (remember, this is the same
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* physical page!)
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* - Now switch to the runtime pgd (same VA, and still the same physical
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* page!)
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* - Invalidate TLBs
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* - Set stack and vectors
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* - Profit! (or eret, if you only care about the code).
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*
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* As we only have four registers available to pass parameters (and we
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* need six), we split the init in two phases:
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* - Phase 1: r0 = 0, r1 = 0, r2,r3 contain the boot PGD.
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* Provides the basic HYP init, and enable the MMU.
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* - Phase 2: r0 = ToS, r1 = vectors, r2,r3 contain the runtime PGD.
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* Switches to the runtime PGD, set stack and vectors.
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*/
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.text
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.pushsection .hyp.idmap.text,"ax"
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.align 5
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__kvm_hyp_init:
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.globl __kvm_hyp_init
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@ Hyp-mode exception vector
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W(b) .
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W(b) .
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W(b) .
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W(b) .
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W(b) .
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W(b) __do_hyp_init
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W(b) .
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W(b) .
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__do_hyp_init:
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cmp r0, #0 @ We have a SP?
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bne phase2 @ Yes, second stage init
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@ Set the HTTBR to point to the hypervisor PGD pointer passed
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mcrr p15, 4, r2, r3, c2
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@ Set the HTCR and VTCR to the same shareability and cacheability
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@ settings as the non-secure TTBCR and with T0SZ == 0.
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mrc p15, 4, r0, c2, c0, 2 @ HTCR
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ldr r2, =HTCR_MASK
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bic r0, r0, r2
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mrc p15, 0, r1, c2, c0, 2 @ TTBCR
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and r1, r1, #(HTCR_MASK & ~TTBCR_T0SZ)
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orr r0, r0, r1
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mcr p15, 4, r0, c2, c0, 2 @ HTCR
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mrc p15, 4, r1, c2, c1, 2 @ VTCR
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ldr r2, =VTCR_MASK
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bic r1, r1, r2
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bic r0, r0, #(~VTCR_HTCR_SH) @ clear non-reusable HTCR bits
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orr r1, r0, r1
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orr r1, r1, #(KVM_VTCR_SL0 | KVM_VTCR_T0SZ | KVM_VTCR_S)
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mcr p15, 4, r1, c2, c1, 2 @ VTCR
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@ Use the same memory attributes for hyp. accesses as the kernel
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@ (copy MAIRx ro HMAIRx).
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mrc p15, 0, r0, c10, c2, 0
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mcr p15, 4, r0, c10, c2, 0
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mrc p15, 0, r0, c10, c2, 1
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mcr p15, 4, r0, c10, c2, 1
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@ Set the HSCTLR to:
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@ - ARM/THUMB exceptions: Kernel config (Thumb-2 kernel)
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@ - Endianness: Kernel config
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@ - Fast Interrupt Features: Kernel config
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@ - Write permission implies XN: disabled
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@ - Instruction cache: enabled
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@ - Data/Unified cache: enabled
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@ - Memory alignment checks: enabled
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@ - MMU: enabled (this code must be run from an identity mapping)
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mrc p15, 4, r0, c1, c0, 0 @ HSCR
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ldr r2, =HSCTLR_MASK
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bic r0, r0, r2
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mrc p15, 0, r1, c1, c0, 0 @ SCTLR
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ldr r2, =(HSCTLR_EE | HSCTLR_FI | HSCTLR_I | HSCTLR_C)
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and r1, r1, r2
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ARM( ldr r2, =(HSCTLR_M | HSCTLR_A) )
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THUMB( ldr r2, =(HSCTLR_M | HSCTLR_A | HSCTLR_TE) )
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orr r1, r1, r2
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orr r0, r0, r1
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isb
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mcr p15, 4, r0, c1, c0, 0 @ HSCR
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@ End of init phase-1
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eret
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phase2:
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@ Set stack pointer
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mov sp, r0
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@ Set HVBAR to point to the HYP vectors
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mcr p15, 4, r1, c12, c0, 0 @ HVBAR
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@ Jump to the trampoline page
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ldr r0, =TRAMPOLINE_VA
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adr r1, target
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bfi r0, r1, #0, #PAGE_SHIFT
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mov pc, r0
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target: @ We're now in the trampoline code, switch page tables
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mcrr p15, 4, r2, r3, c2
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isb
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@ Invalidate the old TLBs
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mcr p15, 4, r0, c8, c7, 0 @ TLBIALLH
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dsb
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eret
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.ltorg
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.globl __kvm_hyp_init_end
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__kvm_hyp_init_end:
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.popsection
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