From 5a677ce044f18a341ab942e23516e52ad89f7687 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 12 Apr 2013 19:12:06 +0100 Subject: ARM: KVM: switch to a dual-step HYP init code 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 Signed-off-by: Christoffer Dall --- arch/arm/include/asm/kvm_mmu.h | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) (limited to 'arch/arm/include/asm/kvm_mmu.h') diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h index 92eb20d57942..24b767a8cdb9 100644 --- a/arch/arm/include/asm/kvm_mmu.h +++ b/arch/arm/include/asm/kvm_mmu.h @@ -19,17 +19,29 @@ #ifndef __ARM_KVM_MMU_H__ #define __ARM_KVM_MMU_H__ -#include -#include +#include +#include /* * We directly use the kernel VA for the HYP, as we can directly share * the mapping (HTTBR "covers" TTBR1). */ -#define HYP_PAGE_OFFSET_MASK (~0UL) +#define HYP_PAGE_OFFSET_MASK UL(~0) #define HYP_PAGE_OFFSET PAGE_OFFSET #define KERN_TO_HYP(kva) (kva) +/* + * Our virtual mapping for the boot-time MMU-enable code. Must be + * shared across all the page-tables. Conveniently, we use the vectors + * page, where no kernel data will ever be shared with HYP. + */ +#define TRAMPOLINE_VA UL(CONFIG_VECTORS_BASE) + +#ifndef __ASSEMBLY__ + +#include +#include + int create_hyp_mappings(void *from, void *to); int create_hyp_io_mappings(void *from, void *to, phys_addr_t); void free_hyp_pgds(void); @@ -44,6 +56,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run); void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu); phys_addr_t kvm_mmu_get_httbr(void); +phys_addr_t kvm_mmu_get_boot_httbr(void); +phys_addr_t kvm_get_idmap_vector(void); int kvm_mmu_init(void); void kvm_clear_hyp_idmap(void); @@ -113,4 +127,8 @@ static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn) } } +#define kvm_flush_dcache_to_poc(a,l) __cpuc_flush_dcache_area((a), (l)) + +#endif /* !__ASSEMBLY__ */ + #endif /* __ARM_KVM_MMU_H__ */ -- cgit v1.2.1