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kvm: x86: Allow userspace to handle emulation errors

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Add a fallback mechanism to the in-kernel instruction emulator that
allows userspace the opportunity to process an instruction the emulator
was unable to.  When the in-kernel instruction emulator fails to process
an instruction it will either inject a #UD into the guest or exit to
userspace with exit reason KVM_INTERNAL_ERROR.  This is because it does
not know how to proceed in an appropriate manner.  This feature lets
userspace get involved to see if it can figure out a better path
forward.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Message-Id: <20210510144834.658457-2-aaronlewis@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Aaron Lewis
2021-05-10 07:48:33 -07:00
committed by Paolo Bonzini
parent 27de925044
commit 19238e75bd
4 changed files with 85 additions and 4 deletions
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23
include/uapi/linux/kvm.h
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@@ -280,6 +280,9 @@ struct kvm_xen_exit {
/* Encounter unexpected vm-exit reason */
#define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4
/* Flags that describe what fields in emulation_failure hold valid data. */
#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0)
/* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
struct kvm_run {
/* in */
@@ -383,6 +386,25 @@ struct kvm_run {
__u32 ndata;
__u64 data[16];
} internal;
/*
* KVM_INTERNAL_ERROR_EMULATION
*
* "struct emulation_failure" is an overlay of "struct internal"
* that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of
* KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error
* sub-types, this struct is ABI! It also needs to be backwards
* compatible with "struct internal". Take special care that
* "ndata" is correct, that new fields are enumerated in "flags",
* and that each flag enumerates fields that are 64-bit aligned
* and sized (so that ndata+internal.data[] is valid/accurate).
*/
struct {
__u32 suberror;
__u32 ndata;
__u64 flags;
__u8 insn_size;
__u8 insn_bytes[15];
} emulation_failure;
/* KVM_EXIT_OSI */
struct {
__u64 gprs[32];
@@ -1088,6 +1110,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_EXIT_HYPERCALL 201
#define KVM_CAP_PPC_RPT_INVALIDATE 202
#define KVM_CAP_BINARY_STATS_FD 203
#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
#ifdef KVM_CAP_IRQ_ROUTING