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Commit 98047888 authored by Christoffer Dall's avatar Christoffer Dall
Browse files

arm/arm64: KVM: Support KVM_CAP_READONLY_MEM 



When userspace loads code and data in a read-only memory regions, KVM
needs to be able to handle this on arm and arm64.  Specifically this is
used when running code directly from a read-only flash device; the
common scenario is a UEFI blob loaded with the -bios option in QEMU.

Note that the MMIO exit on writes to a read-only memory is ABI and can
be used to emulate block-erase style flash devices.

Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent 64d83126

arch/arm/include/uapi/asm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 


#define __KVM_HAVE_GUEST_DEBUG

#define __KVM_HAVE_IRQ_LINE

#define __KVM_HAVE_READONLY_MEM



#define KVM_REG_SIZE(id)						\

	(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))

arch/arm/kvm/arm.c

+1 −0
Original line number Diff line number Diff line
@@ -188,6 +188,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) 
	case KVM_CAP_ONE_REG:

	case KVM_CAP_ARM_PSCI:

	case KVM_CAP_ARM_PSCI_0_2:

	case KVM_CAP_READONLY_MEM:

		r = 1;

		break;

	case KVM_CAP_COALESCED_MMIO:

arch/arm/kvm/mmu.c

+8 −14
Original line number Diff line number Diff line
@@ -747,14 +747,13 @@ static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap) 
}



static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,

			  struct kvm_memory_slot *memslot,

			  struct kvm_memory_slot *memslot, unsigned long hva,

			  unsigned long fault_status)

{

	int ret;

	bool write_fault, writable, hugetlb = false, force_pte = false;

	unsigned long mmu_seq;

	gfn_t gfn = fault_ipa >> PAGE_SHIFT;

	unsigned long hva = gfn_to_hva(vcpu->kvm, gfn);

	struct kvm *kvm = vcpu->kvm;

	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;

	struct vm_area_struct *vma;
@@ -863,7 +862,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run) 
	unsigned long fault_status;

	phys_addr_t fault_ipa;

	struct kvm_memory_slot *memslot;

	bool is_iabt;

	unsigned long hva;

	bool is_iabt, write_fault, writable;

	gfn_t gfn;

	int ret, idx;
@@ -884,7 +884,10 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run) 
	idx = srcu_read_lock(&vcpu->kvm->srcu);



	gfn = fault_ipa >> PAGE_SHIFT;

	if (!kvm_is_visible_gfn(vcpu->kvm, gfn)) {

	memslot = gfn_to_memslot(vcpu->kvm, gfn);

	hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);

	write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));

	if (kvm_is_error_hva(hva) || (write_fault && !writable)) {

		if (is_iabt) {

			/* Prefetch Abort on I/O address */

			kvm_inject_pabt(vcpu, kvm_vcpu_get_hfar(vcpu));
@@ -892,13 +895,6 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run) 
			goto out_unlock;

		}



		if (fault_status != FSC_FAULT) {

			kvm_err("Unsupported fault status on io memory: %#lx\n",

				fault_status);

			ret = -EFAULT;

			goto out_unlock;

		}



		/*

		 * The IPA is reported as [MAX:12], so we need to

		 * complement it with the bottom 12 bits from the
@@ -910,9 +906,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run) 
		goto out_unlock;

	}



	memslot = gfn_to_memslot(vcpu->kvm, gfn);



	ret = user_mem_abort(vcpu, fault_ipa, memslot, fault_status);

	ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);

	if (ret == 0)

		ret = 1;

out_unlock:

arch/arm64/include/uapi/asm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 


#define __KVM_HAVE_GUEST_DEBUG

#define __KVM_HAVE_IRQ_LINE

#define __KVM_HAVE_READONLY_MEM



#define KVM_REG_SIZE(id)						\

	(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))