| Message ID | 20170724200303.12197-27-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Jul 24, 2017 at 03:03:03PM -0500, Brijesh Singh wrote: > On AMD platform, under certain conditions insn_len may be zero on #NPF. "On AMD platforms... " > This can happen if guest gets a page-fault on data access, but HW table " ... if a guest... .. but the HW table walker ..." > walker is not able to read the instruction page (e.g instuction page > is not present in memory). > > Typically, when insn_len is zero, x86_emulate_instruction() walks the > guest page table and fetches the instruction bytes from guest memory. > When SEV is enabled, the guest memory is encrypted with guest-specific > key hence hypervisor will not able to fetch the instruction bytes. > In those cases we simply restart the guest. Same question as in the previous patch: should we make this a proper interface? > I have encountered this issue when running kernbench inside the guest. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > arch/x86/kvm/mmu.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index ccb70b8..be41ad0 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -4850,6 +4850,23 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, > if (mmio_info_in_cache(vcpu, cr2, direct)) > emulation_type = 0; > emulate: > + /* > + * On AMD platform, under certain conditions insn_len may be zero on #NPF. Same typos as above. > + * This can happen if guest gets a page-fault on data access, but HW table > + * walker is not able to read the instruction page (e.g instuction page > + * is not present). > + * > + * Typically, when insn_len is zero, x86_emulate_instruction() walks the > + * guest page table and fetches the instruction bytes. When SEV is active, > + * the guest memory is encrypted with guest key hence we will not able to > + * fetch the instruction bytes. In those cases we simply restart the guest. > + */ > + if (unlikely(!insn_len)) { > + if (kvm_x86_ops->memory_encryption_enabled && > + kvm_x86_ops->memory_encryption_enabled(vcpu)) Align vertically.
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index ccb70b8..be41ad0 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -4850,6 +4850,23 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code, if (mmio_info_in_cache(vcpu, cr2, direct)) emulation_type = 0; emulate: + /* + * On AMD platform, under certain conditions insn_len may be zero on #NPF. + * This can happen if guest gets a page-fault on data access, but HW table + * walker is not able to read the instruction page (e.g instuction page + * is not present). + * + * Typically, when insn_len is zero, x86_emulate_instruction() walks the + * guest page table and fetches the instruction bytes. When SEV is active, + * the guest memory is encrypted with guest key hence we will not able to + * fetch the instruction bytes. In those cases we simply restart the guest. + */ + if (unlikely(!insn_len)) { + if (kvm_x86_ops->memory_encryption_enabled && + kvm_x86_ops->memory_encryption_enabled(vcpu)) + return 1; + } + er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len); switch (er) {
On AMD platform, under certain conditions insn_len may be zero on #NPF. This can happen if guest gets a page-fault on data access, but HW table walker is not able to read the instruction page (e.g instuction page is not present in memory). Typically, when insn_len is zero, x86_emulate_instruction() walks the guest page table and fetches the instruction bytes from guest memory. When SEV is enabled, the guest memory is encrypted with guest-specific key hence hypervisor will not able to fetch the instruction bytes. In those cases we simply restart the guest. I have encountered this issue when running kernbench inside the guest. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- arch/x86/kvm/mmu.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)