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KVM: x86: Add an emulation type to handle completion of user exits

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The next patch would use kvm_emulate_instruction() with
EMULTYPE_SKIP in complete_userspace_io callback to fix a
problem in msr access emulation. However, EMULTYPE_SKIP
only updates RIP, more things like updating interruptibility
state and injecting single-step #DBs would be done in the
callback. Since the emulator also does those things after
x86_emulate_insn(), add a new emulation type to pair with
EMULTYPE_SKIP to do those things for completion of user exits
within the emulator.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <8f8c8e268b65f31d55c2881a4b30670946ecfa0d.1635842679.git.houwenlong93@linux.alibaba.com>
This commit is contained in:
Hou Wenlong 2021-11-02 17:15:30 +08:00 committed by Paolo Bonzini
parent 5e854864ee
commit 906fa90416
2 changed files with 17 additions and 4 deletions
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8
arch/x86/include/asm/kvm_host.h
View File

@ -1643,7 +1643,8 @@ extern u64 kvm_mce_cap_supported;
*
* EMULTYPE_SKIP - Set when emulating solely to skip an instruction, i.e. to
* decode the instruction length. For use *only* by
* kvm_x86_ops.skip_emulated_instruction() implementations.
* kvm_x86_ops.skip_emulated_instruction() implementations if
* EMULTYPE_COMPLETE_USER_EXIT is not set.
*
* EMULTYPE_ALLOW_RETRY_PF - Set when the emulator should resume the guest to
* retry native execution under certain conditions,
@ -1663,6 +1664,10 @@ extern u64 kvm_mce_cap_supported;
*
* EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which
* case the CR2/GPA value pass on the stack is valid.
*
* EMULTYPE_COMPLETE_USER_EXIT - Set when the emulator should update interruptibility
* state and inject single-step #DBs after skipping
* an instruction (after completing userspace I/O).
*/
#define EMULTYPE_NO_DECODE (1 << 0)
#define EMULTYPE_TRAP_UD (1 << 1)
@ -1671,6 +1676,7 @@ extern u64 kvm_mce_cap_supported;
#define EMULTYPE_TRAP_UD_FORCED (1 << 4)
#define EMULTYPE_VMWARE_GP (1 << 5)
#define EMULTYPE_PF (1 << 6)
#define EMULTYPE_COMPLETE_USER_EXIT (1 << 7)
int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,

13
arch/x86/kvm/x86.c
View File

@ -8134,9 +8134,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
}
/*
* Note, EMULTYPE_SKIP is intended for use *only* by vendor callbacks
* for kvm_skip_emulated_instruction(). The caller is responsible for
* updating interruptibility state and injecting single-step #DBs.
* EMULTYPE_SKIP without EMULTYPE_COMPLETE_USER_EXIT is intended for
* use *only* by vendor callbacks for kvm_skip_emulated_instruction().
* The caller is responsible for updating interruptibility state and
* injecting single-step #DBs.
*/
if (emulation_type & EMULTYPE_SKIP) {
if (ctxt->mode != X86EMUL_MODE_PROT64)
@ -8144,6 +8145,11 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
else
ctxt->eip = ctxt->_eip;
if (emulation_type & EMULTYPE_COMPLETE_USER_EXIT) {
r = 1;
goto writeback;
}
kvm_rip_write(vcpu, ctxt->eip);
if (ctxt->eflags & X86_EFLAGS_RF)
kvm_set_rflags(vcpu, ctxt->eflags & ~X86_EFLAGS_RF);
@ -8213,6 +8219,7 @@ restart:
else
r = 1;
writeback:
if (writeback) {
unsigned long rflags = static_call(kvm_x86_get_rflags)(vcpu);
toggle_interruptibility(vcpu, ctxt->interruptibility);