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Date: Thu, 17 Aug 2017 15:17:23 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Yu Zhang <yu.c.zhang@...ux.intel.com>, kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, rkrcmar@...hat.com,
tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
xiaoguangrong@...cent.com, joro@...tes.org
Subject: Re: [PATCH v2 1/5] KVM: x86: Add return value to kvm_cpuid().
On 17/08/2017 14:23, Yu Zhang wrote:
>
>
> On 8/17/2017 8:29 PM, Paolo Bonzini wrote:
>> On 17/08/2017 21:52, Yu Zhang wrote:
>>> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
>>> index ac15193..3e759cf 100644
>>> --- a/arch/x86/kvm/cpuid.h
>>> +++ b/arch/x86/kvm/cpuid.h
>>> @@ -21,7 +21,14 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
>>> int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
>>> struct kvm_cpuid2 *cpuid,
>>> struct kvm_cpuid_entry2 __user *entries);
>>> -void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx,
>>> u32 *edx);
>>> +
>>> +enum {
>>> + NO_CHECK_LIMIT = 0,
>>> + CHECK_LIMIT = 1,
>>> +};
>> emulate.c should not include cpuid.h. The argument can be simply a
>> bool, though.
>
> Thanks, Paolo.
> So we just use true/false in emulate.c & svm.c, is this OK?
> BTW could you please
>
>>> +bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
>>> + u32 *ecx, u32 *edx, int check_limit);
>>> int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);
>>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>>> index fb00559..46daa37 100644
>>> --- a/arch/x86/kvm/emulate.c
>>> +++ b/arch/x86/kvm/emulate.c
>>> @@ -28,6 +28,7 @@
>>> #include "x86.h"
>>> #include "tss.h"
>>> +#include "cpuid.h"
>>> /*
>>> * Operand types
>>> @@ -2333,8 +2334,10 @@ static int emulator_has_longmode(struct
>>> x86_emulate_ctxt *ctxt)
>>> eax = 0x80000001;
>>> ecx = 0;
>>> - ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> - return edx & bit(X86_FEATURE_LM);
>>> + if (ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx,
>>> NO_CHECK_LIMIT))
>>> + return edx & bit(X86_FEATURE_LM);
>>> + else
>>> + return 0;
>>> }
>>> #define GET_SMSTATE(type, smbase, offset) \
>>> @@ -2636,7 +2639,7 @@ static bool vendor_intel(struct
>>> x86_emulate_ctxt *ctxt)
>>> u32 eax, ebx, ecx, edx;
>>> eax = ecx = 0;
>>> - ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> + ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, NO_CHECK_LIMIT);
>>> return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx
>>> && ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx
>>> && edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
>>> @@ -2656,7 +2659,7 @@ static bool em_syscall_is_enabled(struct
>>> x86_emulate_ctxt *ctxt)
>>> eax = 0x00000000;
>>> ecx = 0x00000000;
>>> - ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> + ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, NO_CHECK_LIMIT);
>>> /*
>>> * Intel ("GenuineIntel")
>>> * remark: Intel CPUs only support "syscall" in 64bit
>>> @@ -3551,7 +3554,7 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
>>> /*
>>> * Check MOVBE is set in the guest-visible CPUID leaf.
>>> */
>>> - ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> + ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, CHECK_LIMIT);
>> This should be NO_CHECK_LIMIT.
>>
>> Otherwise okay!
>
> Then I guess check_fxsr() should also use NO_CHECK_LIMIT('false' for a
> bool argument), because it's also for eax=1?
Good point.
> And what about svm_vcpu_reset()?
No, this one should be left as is, it's just writing a register and not
checking a feature.
> I am not sure if leaf 1 is always available. And if the answer is yes, I
> do not think any of these 3 places(em_movbe/check_fxsr/svm_vcpu_reset) will
> need to fall back to check_cpuid_limit(),
> nor do we need to check the return value of get_cpuid(). Do you agree? :-)
I think the answer is no, but you don't need to check the return value
because testing against 0 is okay (if best is NULL, get_cpuid returns 0
for eax/ebx/ecx/edx).
Paolo
>
> Yu
>
>>
>> Paolo
>>
>>> if (!(ecx & FFL(MOVBE)))
>>> return emulate_ud(ctxt);
>>> @@ -3865,7 +3868,7 @@ static int em_cpuid(struct x86_emulate_ctxt
>>> *ctxt)
>>> eax = reg_read(ctxt, VCPU_REGS_RAX);
>>> ecx = reg_read(ctxt, VCPU_REGS_RCX);
>>> - ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> + ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, CHECK_LIMIT);
>>> *reg_write(ctxt, VCPU_REGS_RAX) = eax;
>>> *reg_write(ctxt, VCPU_REGS_RBX) = ebx;
>>> *reg_write(ctxt, VCPU_REGS_RCX) = ecx;
>>> @@ -3924,7 +3927,7 @@ static int check_fxsr(struct x86_emulate_ctxt
>>> *ctxt)
>>> {
>>> u32 eax = 1, ebx, ecx = 0, edx;
>>> - ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
>>> + ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, CHECK_LIMIT);
>>> if (!(edx & FFL(FXSR)))
>>> return emulate_ud(ctxt);
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index 1fa9ee5..9def4a8 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -1580,7 +1580,7 @@ static void svm_vcpu_reset(struct kvm_vcpu
>>> *vcpu, bool init_event)
>>> }
>>> init_vmcb(svm);
>>> - kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
>>> + kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, CHECK_LIMIT);
>>> kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
>>> if (kvm_vcpu_apicv_active(vcpu) && !init_event)
>>> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
>>> index 0a6cc67..8a202c4 100644
>>> --- a/arch/x86/kvm/trace.h
>>> +++ b/arch/x86/kvm/trace.h
>>> @@ -151,8 +151,8 @@ TRACE_EVENT(kvm_fast_mmio,
>>> */
>>> TRACE_EVENT(kvm_cpuid,
>>> TP_PROTO(unsigned int function, unsigned long rax, unsigned
>>> long rbx,
>>> - unsigned long rcx, unsigned long rdx),
>>> - TP_ARGS(function, rax, rbx, rcx, rdx),
>>> + unsigned long rcx, unsigned long rdx, bool found),
>>> + TP_ARGS(function, rax, rbx, rcx, rdx, found),
>>> TP_STRUCT__entry(
>>> __field( unsigned int, function )
>>> @@ -160,6 +160,7 @@ TRACE_EVENT(kvm_cpuid,
>>> __field( unsigned long, rbx )
>>> __field( unsigned long, rcx )
>>> __field( unsigned long, rdx )
>>> + __field( bool, found )
>>> ),
>>> TP_fast_assign(
>>> @@ -168,11 +169,13 @@ TRACE_EVENT(kvm_cpuid,
>>> __entry->rbx = rbx;
>>> __entry->rcx = rcx;
>>> __entry->rdx = rdx;
>>> + __entry->found = found;
>>> ),
>>> - TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx",
>>> + TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx, cpuid entry
>>> %s",
>>> __entry->function, __entry->rax,
>>> - __entry->rbx, __entry->rcx, __entry->rdx)
>>> + __entry->rbx, __entry->rcx, __entry->rdx,
>>> + __entry->found ? "found" : "not found")
>>> );
>>> #define AREG(x) { APIC_##x, "APIC_" #x }
>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index e40a779..ee99fc1 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>> @@ -5213,10 +5213,10 @@ static int emulator_intercept(struct
>>> x86_emulate_ctxt *ctxt,
>>> return kvm_x86_ops->check_intercept(emul_to_vcpu(ctxt), info,
>>> stage);
>>> }
>>> -static void emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
>>> - u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
>>> +static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
>>> + u32 *eax, u32 *ebx, u32 *ecx, u32 *edx, int check_limit)
>>> {
>>> - kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx);
>>> + return kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx,
>>> check_limit);
>>> }
>>> static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt,
>>> unsigned reg)
>>>
>>
>
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