2020-12-14 19:04:28

by Paolo Bonzini

Subject: [PATCH 2/3] KVM: x86: use kvm_complete_insn_gp in emulating RDMSR/WRMSR

Simplify the four functions that handle {kernel,user} {rd,wr}msr, there
is still some repetition between the two instances of rdmsr but the
whole business of calling kvm_inject_gp and kvm_skip_emulated_instruction
can be unified nicely.

Because complete_emulated_wrmsr now becomes essentially a call to
kvm_complete_insn_gp, remove complete_emulated_msr.

Signed-off-by: Paolo Bonzini <[email protected]>
---
arch/x86/kvm/x86.c | 42 ++++++++++++++++--------------------------
1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a3fdc16cfd6f..2f1bc52e70c0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1634,27 +1634,20 @@ int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
}
EXPORT_SYMBOL_GPL(kvm_set_msr);

-static int complete_emulated_msr(struct kvm_vcpu *vcpu, bool is_read)
+static int complete_emulated_rdmsr(struct kvm_vcpu *vcpu)
{
- if (vcpu->run->msr.error) {
- kvm_inject_gp(vcpu, 0);
- return 1;
- } else if (is_read) {
+ int err = vcpu->run->msr.error;
+ if (!err) {
kvm_rax_write(vcpu, (u32)vcpu->run->msr.data);
kvm_rdx_write(vcpu, vcpu->run->msr.data >> 32);
}

- return kvm_skip_emulated_instruction(vcpu);
-}
-
-static int complete_emulated_rdmsr(struct kvm_vcpu *vcpu)
-{
- return complete_emulated_msr(vcpu, true);
+ return kvm_complete_insn_gp(vcpu, err);
}

static int complete_emulated_wrmsr(struct kvm_vcpu *vcpu)
{
- return complete_emulated_msr(vcpu, false);
+ return kvm_complete_insn_gp(vcpu, vcpu->run->msr.error);
}

static u64 kvm_msr_reason(int r)
@@ -1718,17 +1711,16 @@ int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu)
}

/* MSR read failed? Inject a #GP */
- if (r) {
+ if (!r) {
+ trace_kvm_msr_read(ecx, data);
+
+ kvm_rax_write(vcpu, data & -1u);
+ kvm_rdx_write(vcpu, (data >> 32) & -1u);
+ } else {
trace_kvm_msr_read_ex(ecx);
- kvm_inject_gp(vcpu, 0);
- return 1;
}

- trace_kvm_msr_read(ecx, data);
-
- kvm_rax_write(vcpu, data & -1u);
- kvm_rdx_write(vcpu, (data >> 32) & -1u);
- return kvm_skip_emulated_instruction(vcpu);
+ return kvm_complete_insn_gp(vcpu, r);
}
EXPORT_SYMBOL_GPL(kvm_emulate_rdmsr);

@@ -1750,14 +1742,12 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu)
return r;

/* MSR write failed? Inject a #GP */
- if (r > 0) {
+ if (!r)
+ trace_kvm_msr_write(ecx, data);
+ else
trace_kvm_msr_write_ex(ecx, data);
- kvm_inject_gp(vcpu, 0);
- return 1;
- }

- trace_kvm_msr_write(ecx, data);
- return kvm_skip_emulated_instruction(vcpu);
+ return kvm_complete_insn_gp(vcpu, r);
}
EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);

--
2.26.2

2020-12-14 20:56:12

by Tom Lendacky

Subject: Re: [PATCH 2/3] KVM: x86: use kvm_complete_insn_gp in emulating RDMSR/WRMSR

On 12/14/20 12:32 PM, Paolo Bonzini wrote:
> Simplify the four functions that handle {kernel,user} {rd,wr}msr, there
> is still some repetition between the two instances of rdmsr but the
> whole business of calling kvm_inject_gp and kvm_skip_emulated_instruction
> can be unified nicely.
>
> Because complete_emulated_wrmsr now becomes essentially a call to
> kvm_complete_insn_gp, remove complete_emulated_msr.
>
> Signed-off-by: Paolo Bonzini <[email protected]>

Just two minor nits below.

Reviewed-by: Tom Lendacky <[email protected]>

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a3fdc16cfd6f..2f1bc52e70c0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1634,27 +1634,20 @@ int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
> }
> EXPORT_SYMBOL_GPL(kvm_set_msr);
>
>
> /* MSR read failed? Inject a #GP */

This comment isn't accurate any more, maybe just delete it?

> - if (r) {
> + if (!r) {
> + trace_kvm_msr_read(ecx, data);
> +
> + kvm_rax_write(vcpu, data & -1u);
> + kvm_rdx_write(vcpu, (data >> 32) & -1u);
> + } else {
> trace_kvm_msr_read_ex(ecx);
> - kvm_inject_gp(vcpu, 0);
> - return 1;
> }
>
> - trace_kvm_msr_read(ecx, data);
> -
> - kvm_rax_write(vcpu, data & -1u);
> - kvm_rdx_write(vcpu, (data >> 32) & -1u);
> - return kvm_skip_emulated_instruction(vcpu);
> + return kvm_complete_insn_gp(vcpu, r);
> }
> EXPORT_SYMBOL_GPL(kvm_emulate_rdmsr);
>
> @@ -1750,14 +1742,12 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu)
> return r;
>
> /* MSR write failed? Inject a #GP */

Ditto on this comment.

Thanks,
Tom

> - if (r > 0) {
> + if (!r)
> + trace_kvm_msr_write(ecx, data);
> + else
> trace_kvm_msr_write_ex(ecx, data);
> - kvm_inject_gp(vcpu, 0);
> - return 1;
> - }
>
> - trace_kvm_msr_write(ecx, data);
> - return kvm_skip_emulated_instruction(vcpu);
> + return kvm_complete_insn_gp(vcpu, r);
> }
> EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);
>
>