Re: [Xen-devel] [PATCH v4 4/4] x86: make hvm_cpuid() tolerate NULL pointers

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/23/2013 06:12 AM, Jan Beulich wrote:
> Now that we other HVM code start making more extensive use of
Something is wrong with this sentence. I think "we" is not needed.

Other than that

Acked-by:  Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>


-boris

> hvm_cpuid(), let's not force every caller to declare dummy variables
> for output not cared about.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2757,7 +2757,17 @@ void hvm_cpuid(unsigned int input, unsig
>   {
>       struct vcpu *v = current;
>       struct domain *d = v->domain;
> -    unsigned int count = *ecx;
> +    unsigned int count, dummy = 0;
> +
> +    if ( !eax )
> +        eax = &dummy;
> +    if ( !ebx )
> +        ebx = &dummy;
> +    if ( !ecx )
> +        ecx = &dummy;
> +    count = *ecx;
> +    if ( !edx )
> +        edx = &dummy;
>   
>       if ( cpuid_viridian_leaves(input, eax, ebx, ecx, edx) )
>           return;
> @@ -2765,7 +2775,7 @@ void hvm_cpuid(unsigned int input, unsig
>       if ( cpuid_hypervisor_leaves(input, count, eax, ebx, ecx, edx) )
>           return;
>   
> -    domain_cpuid(d, input, *ecx, eax, ebx, ecx, edx);
> +    domain_cpuid(d, input, count, eax, ebx, ecx, edx);
>   
>       switch ( input )
>       {
> @@ -2853,15 +2863,15 @@ int hvm_msr_read_intercept(unsigned int
>   {
>       struct vcpu *v = current;
>       uint64_t *var_range_base, *fixed_range_base;
> -    int index, mtrr;
> -    uint32_t cpuid[4];
> +    bool_t mtrr;
> +    unsigned int edx, index;
>       int ret = X86EMUL_OKAY;
>   
>       var_range_base = (uint64_t *)v->arch.hvm_vcpu.mtrr.var_ranges;
>       fixed_range_base = (uint64_t *)v->arch.hvm_vcpu.mtrr.fixed_ranges;
>   
> -    hvm_cpuid(1, &cpuid[0], &cpuid[1], &cpuid[2], &cpuid[3]);
> -    mtrr = !!(cpuid[3] & cpufeat_mask(X86_FEATURE_MTRR));
> +    hvm_cpuid(1, NULL, NULL, NULL, &edx);
> +    mtrr = !!(edx & cpufeat_mask(X86_FEATURE_MTRR));
>   
>       switch ( msr )
>       {
> @@ -2969,15 +2979,15 @@ int hvm_msr_read_intercept(unsigned int
>   int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content)
>   {
>       struct vcpu *v = current;
> -    int index, mtrr;
> -    uint32_t cpuid[4];
> +    bool_t mtrr;
> +    unsigned int edx, index;
>       int ret = X86EMUL_OKAY;
>   
>       HVMTRACE_3D(MSR_WRITE, msr,
>                  (uint32_t)msr_content, (uint32_t)(msr_content >> 32));
>   
> -    hvm_cpuid(1, &cpuid[0], &cpuid[1], &cpuid[2], &cpuid[3]);
> -    mtrr = !!(cpuid[3] & cpufeat_mask(X86_FEATURE_MTRR));
> +    hvm_cpuid(1, NULL, NULL, NULL, &edx);
> +    mtrr = !!(edx & cpufeat_mask(X86_FEATURE_MTRR));
>   
>       hvm_memory_event_msr(msr, msr_content);
>   
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -806,13 +806,13 @@ static inline void svm_lwp_load(struct v
>   /* Update LWP_CFG MSR (0xc0000105). Return -1 if error; otherwise returns 0. 
> */
>   static int svm_update_lwp_cfg(struct vcpu *v, uint64_t msr_content)
>   {
> -    unsigned int eax, ebx, ecx, edx;
> +    unsigned int edx;
>       uint32_t msr_low;
>       static uint8_t lwp_intr_vector;
>   
>       if ( xsave_enabled(v) && cpu_has_lwp )
>       {
> -        hvm_cpuid(0x8000001c, &eax, &ebx, &ecx, &edx);
> +        hvm_cpuid(0x8000001c, NULL, NULL, NULL, &edx);
>           msr_low = (uint32_t)msr_content;
>           
>           /* generate #GP if guest tries to turn on unsupported features. */
> @@ -1163,10 +1163,10 @@ static void svm_init_erratum_383(struct
>   
>   static int svm_handle_osvw(struct vcpu *v, uint32_t msr, uint64_t *val, bool_t read)
>   {
> -    uint eax, ebx, ecx, edx;
> +    unsigned int ecx;
>   
>       /* Guest OSVW support */
> -    hvm_cpuid(0x80000001, &eax, &ebx, &ecx, &edx);
> +    hvm_cpuid(0x80000001, NULL, NULL, &ecx, NULL);
>       if ( !test_bit((X86_FEATURE_OSVW & 31), &ecx) )
>           return -1;
>   
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -1813,7 +1813,7 @@ int nvmx_handle_invvpid(struct cpu_user_
>   int nvmx_msr_read_intercept(unsigned int msr, u64 *msr_content)
>   {
>       struct vcpu *v = current;
> -    unsigned int eax, ebx, ecx, edx, dummy;
> +    unsigned int eax, ebx, ecx, edx;
>       u64 data = 0, host_data = 0;
>       int r = 1;
>   
> @@ -1821,7 +1821,7 @@ int nvmx_msr_read_intercept(unsigned int
>           return 0;
>   
>       /* VMX capablity MSRs are available only when guest supports VMX. */
> -    hvm_cpuid(0x1, &dummy, &dummy, &ecx, &edx);
> +    hvm_cpuid(0x1, NULL, NULL, &ecx, &edx);
>       if ( !(ecx & cpufeat_mask(X86_FEATURE_VMXE)) )
>           return 0;
>   
> @@ -1972,18 +1972,18 @@ int nvmx_msr_read_intercept(unsigned int
>           if ( ecx & cpufeat_mask(X86_FEATURE_XSAVE) )
>               data |= X86_CR4_OSXSAVE;
>   
> -        hvm_cpuid(0x0, &eax, &dummy, &dummy, &dummy);
> +        hvm_cpuid(0x0, &eax, NULL, NULL, NULL);
>           switch ( eax )
>           {
>           default:
> -            hvm_cpuid(0xa, &eax, &dummy, &dummy, &dummy);
> +            hvm_cpuid(0xa, &eax, NULL, NULL, NULL);
>               /* Check whether guest has the perf monitor feature. */
>               if ( (eax & 0xff) && (eax & 0xff00) )
>                   data |= X86_CR4_PCE;
>               /* fall through */
>           case 0x7 ... 0x9:
>               ecx = 0;
> -            hvm_cpuid(0x7, &dummy, &ebx, &ecx, &dummy);
> +            hvm_cpuid(0x7, NULL, &ebx, &ecx, NULL);
>               if ( ebx & cpufeat_mask(X86_FEATURE_FSGSBASE) )
>                   data |= X86_CR4_FSGSBASE;
>               if ( ebx & cpufeat_mask(X86_FEATURE_SMEP) )

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