KVM: x86: fix vcpu->mmio_fragments overflow
After commit b3356bf0db (KVM: emulator: optimize "rep ins" handling),
the pieces of io data can be collected and write them to the guest memory
or MMIO together
Unfortunately, kvm splits the mmio access into 8 bytes and store them to
vcpu->mmio_fragments. If the guest uses "rep ins" to move large data, it
will cause vcpu->mmio_fragments overflow
The bug can be exposed by isapc (-M isapc):
[23154.818733] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
[ ......]
[23154.858083] Call Trace:
[23154.859874] [<ffffffffa04f0e17>] kvm_get_cr8+0x1d/0x28 [kvm]
[23154.861677] [<ffffffffa04fa6d4>] kvm_arch_vcpu_ioctl_run+0xcda/0xe45 [kvm]
[23154.863604] [<ffffffffa04f5a1a>] ? kvm_arch_vcpu_load+0x17b/0x180 [kvm]
Actually, we can use one mmio_fragment to store a large mmio access then
split it when we pass the mmio-exit-info to userspace. After that, we only
need two entries to store mmio info for the cross-mmio pages access
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
hifive-unleashed-5.1
Xiao Guangrong
Marcelo Tosatti
parent
35fd3dc58d
commit
87da7e66a4
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@ -3779,7 +3779,7 @@ static int write_exit_mmio(struct kvm_vcpu *vcpu, gpa_t gpa,
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{
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struct kvm_mmio_fragment *frag = &vcpu->mmio_fragments[0];
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memcpy(vcpu->run->mmio.data, frag->data, frag->len);
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memcpy(vcpu->run->mmio.data, frag->data, min(8u, frag->len));
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return X86EMUL_CONTINUE;
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}
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@ -3832,18 +3832,11 @@ mmio:
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bytes -= handled;
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val += handled;
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while (bytes) {
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unsigned now = min(bytes, 8U);
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frag = &vcpu->mmio_fragments[vcpu->mmio_nr_fragments++];
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frag->gpa = gpa;
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frag->data = val;
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frag->len = now;
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gpa += now;
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val += now;
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bytes -= now;
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}
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WARN_ON(vcpu->mmio_nr_fragments >= KVM_MAX_MMIO_FRAGMENTS);
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frag = &vcpu->mmio_fragments[vcpu->mmio_nr_fragments++];
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frag->gpa = gpa;
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frag->data = val;
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frag->len = bytes;
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return X86EMUL_CONTINUE;
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}
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@ -3890,7 +3883,7 @@ int emulator_read_write(struct x86_emulate_ctxt *ctxt, unsigned long addr,
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vcpu->mmio_needed = 1;
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vcpu->mmio_cur_fragment = 0;
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vcpu->run->mmio.len = vcpu->mmio_fragments[0].len;
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vcpu->run->mmio.len = min(8u, vcpu->mmio_fragments[0].len);
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vcpu->run->mmio.is_write = vcpu->mmio_is_write = ops->write;
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vcpu->run->exit_reason = KVM_EXIT_MMIO;
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vcpu->run->mmio.phys_addr = gpa;
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@ -5522,28 +5515,44 @@ static int complete_emulated_pio(struct kvm_vcpu *vcpu)
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*
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* read:
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* for each fragment
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* write gpa, len
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* exit
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* copy data
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* for each mmio piece in the fragment
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* write gpa, len
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* exit
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* copy data
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* execute insn
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*
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* write:
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* for each fragment
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* write gpa, len
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* copy data
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* exit
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* for each mmio piece in the fragment
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* write gpa, len
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* copy data
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* exit
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*/
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static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
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{
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struct kvm_run *run = vcpu->run;
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struct kvm_mmio_fragment *frag;
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unsigned len;
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BUG_ON(!vcpu->mmio_needed);
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/* Complete previous fragment */
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frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment++];
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frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment];
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len = min(8u, frag->len);
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if (!vcpu->mmio_is_write)
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memcpy(frag->data, run->mmio.data, frag->len);
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memcpy(frag->data, run->mmio.data, len);
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if (frag->len <= 8) {
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/* Switch to the next fragment. */
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frag++;
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vcpu->mmio_cur_fragment++;
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} else {
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/* Go forward to the next mmio piece. */
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frag->data += len;
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frag->gpa += len;
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frag->len -= len;
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}
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if (vcpu->mmio_cur_fragment == vcpu->mmio_nr_fragments) {
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vcpu->mmio_needed = 0;
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if (vcpu->mmio_is_write)
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@ -5551,13 +5560,12 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
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vcpu->mmio_read_completed = 1;
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return complete_emulated_io(vcpu);
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}
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/* Initiate next fragment */
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++frag;
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run->exit_reason = KVM_EXIT_MMIO;
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run->mmio.phys_addr = frag->gpa;
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if (vcpu->mmio_is_write)
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memcpy(run->mmio.data, frag->data, frag->len);
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run->mmio.len = frag->len;
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memcpy(run->mmio.data, frag->data, min(8u, frag->len));
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run->mmio.len = min(8u, frag->len);
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run->mmio.is_write = vcpu->mmio_is_write;
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vcpu->arch.complete_userspace_io = complete_emulated_mmio;
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return 0;
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@ -42,19 +42,8 @@
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*/
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#define KVM_MEMSLOT_INVALID (1UL << 16)
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/*
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* If we support unaligned MMIO, at most one fragment will be split into two:
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*/
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#ifdef KVM_UNALIGNED_MMIO
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# define KVM_EXTRA_MMIO_FRAGMENTS 1
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#else
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# define KVM_EXTRA_MMIO_FRAGMENTS 0
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#endif
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#define KVM_USER_MMIO_SIZE 8
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#define KVM_MAX_MMIO_FRAGMENTS \
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(KVM_MMIO_SIZE / KVM_USER_MMIO_SIZE + KVM_EXTRA_MMIO_FRAGMENTS)
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/* Two fragments for cross MMIO pages. */
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#define KVM_MAX_MMIO_FRAGMENTS 2
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/*
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* For the normal pfn, the highest 12 bits should be zero,
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