On 26/08/14 12:43, Christoffer Dall wrote:
> 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.
>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
M.
> ---
> Changelog[v3]:
> - Remove the check for fault_status != FSC_FAULT in the I/O memory
> abort section, since we now do support permission faults on I/O
> regions. Reported-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Changelog[v2]:
> - None
>
> arch/arm/include/uapi/asm/kvm.h | 1 +
> arch/arm/kvm/arm.c | 1 +
> arch/arm/kvm/mmu.c | 22 ++++++++--------------
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> 4 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> index e6ebdd3..51257fd 100644
> --- a/arch/arm/include/uapi/asm/kvm.h
> +++ b/arch/arm/include/uapi/asm/kvm.h
> @@ -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))
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 9f788eb..ac306b4 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -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:
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 16e7994..62f5642 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -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:
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index e633ff8..f4ec5a6 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -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))
>
--
Jazz is not dead. It just smells funny...
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