Commit f049729c authored by James Hogan's avatar James Hogan Committed by Paolo Bonzini
Browse files

MIPS: KVM: Fix preemptable kvm_mips_get_*_asid() calls 



There are a couple of places in KVM fault handling code which implicitly
use smp_processor_id() via kvm_mips_get_kernel_asid() and
kvm_mips_get_user_asid() from preemptable context. This is unsafe as a
preemption could cause the guest kernel ASID to be changed, resulting in
a host TLB entry being written with the wrong ASID.

Fix by disabling preemption around the kvm_mips_get_*_asid() call and
the corresponding kvm_mips_host_tlb_write().

Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b45bacd2

arch/mips/kvm/tlb.c

+18 −8
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr, 
	int even;

	struct kvm *kvm = vcpu->kvm;

	const int flush_dcache_mask = 0;

	int ret;



	if (KVM_GUEST_KSEGX(badvaddr) != KVM_GUEST_KSEG0) {

		kvm_err("%s: Invalid BadVaddr: %#lx\n", __func__, badvaddr);
@@ -299,14 +300,18 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr, 
		pfn1 = kvm->arch.guest_pmap[gfn];

	}



	entryhi = (vaddr | kvm_mips_get_kernel_asid(vcpu));

	entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) | (0x3 << 3) |

		   (1 << 2) | (0x1 << 1);

	entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) | (0x3 << 3) |

		   (1 << 2) | (0x1 << 1);



	return kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,

	preempt_disable();

	entryhi = (vaddr | kvm_mips_get_kernel_asid(vcpu));

	ret = kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,

				      flush_dcache_mask);

	preempt_enable();



	return ret;

}

EXPORT_SYMBOL_GPL(kvm_mips_handle_kseg0_tlb_fault);
@@ -361,6 +366,7 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu, 
	unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;

	struct kvm *kvm = vcpu->kvm;

	kvm_pfn_t pfn0, pfn1;

	int ret;



	if ((tlb->tlb_hi & VPN2_MASK) == 0) {

		pfn0 = 0;
@@ -387,9 +393,6 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu, 
		*hpa1 = pfn1 << PAGE_SHIFT;



	/* Get attributes from the Guest TLB */

	entryhi = (tlb->tlb_hi & VPN2_MASK) | (KVM_GUEST_KERNEL_MODE(vcpu) ?

					       kvm_mips_get_kernel_asid(vcpu) :

					       kvm_mips_get_user_asid(vcpu));

	entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) | (0x3 << 3) |

		   (tlb->tlb_lo0 & MIPS3_PG_D) | (tlb->tlb_lo0 & MIPS3_PG_V);

	entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) | (0x3 << 3) |
@@ -398,8 +401,15 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu, 
	kvm_debug("@ %#lx tlb_lo0: 0x%08lx tlb_lo1: 0x%08lx\n", vcpu->arch.pc,

		  tlb->tlb_lo0, tlb->tlb_lo1);



	return kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,

	preempt_disable();

	entryhi = (tlb->tlb_hi & VPN2_MASK) | (KVM_GUEST_KERNEL_MODE(vcpu) ?

					       kvm_mips_get_kernel_asid(vcpu) :

					       kvm_mips_get_user_asid(vcpu));

	ret = kvm_mips_host_tlb_write(vcpu, entryhi, entrylo0, entrylo1,

				      tlb->tlb_mask);

	preempt_enable();



	return ret;

}

EXPORT_SYMBOL_GPL(kvm_mips_handle_mapped_seg_tlb_fault);

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