| Message ID | 1536220964-8412-1-git-send-email-wang.yi59@zte.com.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: fix failure of injecting exceptions in x86_emulate_instruction | expand |
On 06/09/2018 10:02, Yi Wang wrote: > In order to fix a page table walk issue, commit 6ea6e84309ca > ("KVM: x86: inject exceptions produced by x86_decode_insn") check > if variable ctxt->have_exception true and inject the exception. > Unfortunately, ctxt->have_exception is set to true only in function > x86_emulate_insn(), which won't be called before invoking > inject_emulated_exception() in the 6ea6e84309ca. > This patch fix this issue. > > Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> > Reviewed-by: Xi Xu <xu.xi8@zte.com.cn> Queued, thanks. Do you have a testcase for this? > --- > arch/x86/kvm/emulate.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 106482d..aecf9a72 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -5105,8 +5105,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) > memcpy(ctxt->fetch.data, insn, insn_len); > else { > rc = __do_insn_fetch_bytes(ctxt, 1); > - if (rc != X86EMUL_CONTINUE) > + if (rc != X86EMUL_CONTINUE) { > + if (rc == X86EMUL_PROPAGATE_FAULT) > + ctxt->have_exception = true; > return rc; > + } > } > > switch (mode) { >
On 20/09/2018 18:30, Paolo Bonzini wrote: > On 06/09/2018 10:02, Yi Wang wrote: >> In order to fix a page table walk issue, commit 6ea6e84309ca >> ("KVM: x86: inject exceptions produced by x86_decode_insn") check >> if variable ctxt->have_exception true and inject the exception. >> Unfortunately, ctxt->have_exception is set to true only in function >> x86_emulate_insn(), which won't be called before invoking >> inject_emulated_exception() in the 6ea6e84309ca. >> This patch fix this issue. >> >> Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> >> Reviewed-by: Xi Xu <xu.xi8@zte.com.cn> > > Queued, thanks. Do you have a testcase for this? Unqueued, sorry. The hypercall test from kvm-unit-tests fails. A VMCALL on the "edge" of canonical address space, i.e. at 0x7ffffffffffd, raises a general protection fault before this patch and a double fault afterwards. Paolo
+cc Peng Hao and Jiang Biao On Thu, Sep 20, 2018 at 06:53:55PM +0200, Paolo Bonzini wrote: > On 20/09/2018 18:30, Paolo Bonzini wrote: > > On 06/09/2018 10:02, Yi Wang wrote: > >> In order to fix a page table walk issue, commit 6ea6e84309ca > >> ("KVM: x86: inject exceptions produced by x86_decode_insn") check > >> if variable ctxt->have_exception true and inject the exception. > >> Unfortunately, ctxt->have_exception is set to true only in function > >> x86_emulate_insn(), which won't be called before invoking > >> inject_emulated_exception() in the 6ea6e84309ca. > >> This patch fix this issue. > >> > >> Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> > >> Reviewed-by: Xi Xu <xu.xi8@zte.com.cn> > > > > Queued, thanks. Do you have a testcase for this? > > Unqueued, sorry. The hypercall test from kvm-unit-tests fails. A > VMCALL on the "edge" of canonical address space, i.e. at 0x7ffffffffffd, > raises a general protection fault before this patch and a double fault > afterwards. Peng Hao submitted a very similar patch[1], the difference being that it also modified x86_emulate_instruction() to ignore the result of inject_emulated_exception(). I have no idea if that change is correct but it may be related to the aforementioned unit test failing. [1] https://lkml.org/lkml/2018/9/19/38
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 106482d..aecf9a72 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -5105,8 +5105,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) memcpy(ctxt->fetch.data, insn, insn_len); else { rc = __do_insn_fetch_bytes(ctxt, 1); - if (rc != X86EMUL_CONTINUE) + if (rc != X86EMUL_CONTINUE) { + if (rc == X86EMUL_PROPAGATE_FAULT) + ctxt->have_exception = true; return rc; + } } switch (mode) {
In order to fix a page table walk issue, commit 6ea6e84309ca ("KVM: x86: inject exceptions produced by x86_decode_insn") check if variable ctxt->have_exception true and inject the exception. Unfortunately, ctxt->have_exception is set to true only in function x86_emulate_insn(), which won't be called before invoking inject_emulated_exception() in the 6ea6e84309ca. This patch fix this issue. Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> Reviewed-by: Xi Xu <xu.xi8@zte.com.cn> --- arch/x86/kvm/emulate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)