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KVM: x86/mmu: Return RET_PF* instead of 1 in kvm_mmu_page_fault()

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Return RET_PF* (excluding RET_PF_EMULATE/RET_PF_CONTINUE/RET_PF_INVALID)
instead of 1 in kvm_mmu_page_fault().

The callers of kvm_mmu_page_fault() are KVM page fault handlers (i.e.,
npf_interception(), handle_ept_misconfig(), __vmx_handle_ept_violation(),
kvm_handle_page_fault()). They either check if the return value is > 0 (as
in npf_interception()) or pass it further to vcpu_run() to decide whether
to break out of the kernel loop and return to the user when r <= 0.
Therefore, returning any positive value is equivalent to returning 1.

Warn if r == RET_PF_CONTINUE (which should not be a valid value) to ensure
a positive return value.

This is a preparation to allow TDX's EPT violation handler to check the
RET_PF* value and retry internally for RET_PF_RETRY.

No functional changes are intended.

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Message-ID: <20250113021138.18875-1-yan.y.zhao@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Yan Zhao 2025-01-13 10:11:38 +08:00 committed by Paolo Bonzini
parent 2c3412e999
commit 7c54803863
2 changed files with 18 additions and 4 deletions
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10
arch/x86/kvm/mmu/mmu.c
View File

@ -6111,8 +6111,16 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
else if (r == RET_PF_SPURIOUS)
vcpu->stat.pf_spurious++;
/*
* None of handle_mmio_page_fault(), kvm_mmu_do_page_fault(), or
* kvm_mmu_write_protect_fault() return RET_PF_CONTINUE.
* kvm_mmu_do_page_fault() only uses RET_PF_CONTINUE internally to
* indicate continuing the page fault handling until to the final
* page table mapping phase.
*/
WARN_ON_ONCE(r == RET_PF_CONTINUE);
if (r != RET_PF_EMULATE)
return 1;
return r;
emulate:
return x86_emulate_instruction(vcpu, cr2_or_gpa, emulation_type, insn,

12
arch/x86/kvm/mmu/mmu_internal.h
View File

@ -315,9 +315,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);
* tracepoints via TRACE_DEFINE_ENUM() in mmutrace.h
*
* Note, all values must be greater than or equal to zero so as not to encroach
* on -errno return values. Somewhat arbitrarily use '0' for CONTINUE, which
* will allow for efficient machine code when checking for CONTINUE, e.g.
* "TEST %rax, %rax, JNZ", as all "stop!" values are non-zero.
* on -errno return values.
*/
enum {
RET_PF_CONTINUE = 0,
@ -329,6 +327,14 @@ enum {
RET_PF_SPURIOUS,
};
/*
* Define RET_PF_CONTINUE as 0 to allow for
* - efficient machine code when checking for CONTINUE, e.g.
* "TEST %rax, %rax, JNZ", as all "stop!" values are non-zero,
* - kvm_mmu_do_page_fault() to return other RET_PF_* as a positive value.
*/
static_assert(RET_PF_CONTINUE == 0);
static inline void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{