[dpdk-dev] [RFC UNTESTED PATCH] eal_common_cpuflags: Fix %rbx corruption, and simplify the code

Neil Horman nhorman at tuxdriver.com
Thu Mar 20 19:59:17 CET 2014


On Thu, Mar 20, 2014 at 02:04:43PM -0400, Neil Horman wrote:
> On Thu, Mar 20, 2014 at 12:39:21PM -0400, Neil Horman wrote:
> > On Thu, Mar 20, 2014 at 08:53:50AM -0700, H. Peter Anvin wrote:
> > > Neil Horman reported that on x86-64 the upper half of %rbx would get
> > > clobbered when the code was compiled PIC or PIE, because the
> > > i386-specific code to preserve %ebx was incorrectly compiled.
> > > 
> > > However, the code is really way more complex than it needs to be.  For
> > > one thing, the CPUID instruction only needs %eax (leaf) and %ecx
> > > (subleaf) as parameters, and since we are testing for bits, we might
> > > as well list the bits explicitly.  Furthermore, we can use an array
> > > rather than doing a switch statement inside a structure.
> > > 
> > > Reported-by: Neil Horman <nhorman at tuxdriver.com>
> > > Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
> > Acked-by: Neil Horman <nhorman at tuxdriver.com>
> > 
> Sorry, I'm just acking the proposed change, I've not tested it yet, though based
> on our conversation, this is the right thing to do.  I'll have test reports
> shortly.
> Neil
> 
Yeah, on testing there are some build and functional errors in this.  Notes
inline


> > > ---
> > >  lib/librte_eal/common/eal_common_cpuflags.c | 272 +++++++++++++---------------
> > >  1 file changed, 121 insertions(+), 151 deletions(-)
> > > 
> > > diff --git a/lib/librte_eal/common/eal_common_cpuflags.c b/lib/librte_eal/common/eal_common_cpuflags.c
> > > index 1ebf78cc2a48..bf66ad9d94ec 100644
> > > --- a/lib/librte_eal/common/eal_common_cpuflags.c
> > > +++ b/lib/librte_eal/common/eal_common_cpuflags.c
> > > @@ -54,21 +54,12 @@
> > >   */
> > >  enum cpu_register_t {
> > >  	REG_EAX = 0,
> > > -	REG_EBX,
> > >  	REG_ECX,
> > >  	REG_EDX,
> > > +	REG_EBX,
> > >  };
> > >  
> > > -/**
> > > - * Parameters for CPUID instruction
> > > - */
> > > -struct cpuid_parameters_t {
> > > -	uint32_t eax;
> > > -	uint32_t ebx;
> > > -	uint32_t ecx;
> > > -	uint32_t edx;
> > > -	enum cpu_register_t return_register;
> > > -};
> > > +typedef uint32_t cpuid_registers_t[4];
> > >  
> > >  #define CPU_FLAG_NAME_MAX_LEN 64
> > >  
> > > @@ -78,8 +69,10 @@ struct cpuid_parameters_t {
> > >  struct feature_entry {
> > >  	enum rte_cpu_flag_t feature;            /**< feature name */
> > >  	char name[CPU_FLAG_NAME_MAX_LEN];       /**< String for printing */
> > > -	struct cpuid_parameters_t params;       /**< cpuid parameters */
> > > -	uint32_t feature_mask;                  /**< bitmask for feature */
> > > +	uint32_t leaf;				/**< cpuid leaf */
> > > +	uint32_t subleaf;			/**< cpuid subleaf */
> > > +	uint32_t reg;				/**< cpuid register */
> > > +	uint32_t bit;				/**< cpuid register bit */
> > >  };
> > >  
> > >  #define FEAT_DEF(f) RTE_CPUFLAG_##f, #f
> > > @@ -88,97 +81,97 @@ struct feature_entry {
> > >   * An array that holds feature entries
> > >   */
> > >  static const struct feature_entry cpu_feature_table[] = {
> > > -	{FEAT_DEF(SSE3),              {0x1, 0, 0, 0, REG_ECX}, 0x00000001},
> > > -	{FEAT_DEF(PCLMULQDQ),         {0x1, 0, 0, 0, REG_ECX}, 0x00000002},
> > > -	{FEAT_DEF(DTES64),            {0x1, 0, 0, 0, REG_ECX}, 0x00000004},
> > > -	{FEAT_DEF(MONITOR),           {0x1, 0, 0, 0, REG_ECX}, 0x00000008},
> > > -	{FEAT_DEF(DS_CPL),            {0x1, 0, 0, 0, REG_ECX}, 0x00000010},
> > > -	{FEAT_DEF(VMX),               {0x1, 0, 0, 0, REG_ECX}, 0x00000020},
> > > -	{FEAT_DEF(SMX),               {0x1, 0, 0, 0, REG_ECX}, 0x00000040},
> > > -	{FEAT_DEF(EIST),              {0x1, 0, 0, 0, REG_ECX}, 0x00000080},
> > > -	{FEAT_DEF(TM2),               {0x1, 0, 0, 0, REG_ECX}, 0x00000100},
> > > -	{FEAT_DEF(SSSE3),             {0x1, 0, 0, 0, REG_ECX}, 0x00000200},
> > > -	{FEAT_DEF(CNXT_ID),           {0x1, 0, 0, 0, REG_ECX}, 0x00000400},
> > > -	{FEAT_DEF(FMA),               {0x1, 0, 0, 0, REG_ECX}, 0x00001000},
> > > -	{FEAT_DEF(CMPXCHG16B),        {0x1, 0, 0, 0, REG_ECX}, 0x00002000},
> > > -	{FEAT_DEF(XTPR),              {0x1, 0, 0, 0, REG_ECX}, 0x00004000},
> > > -	{FEAT_DEF(PDCM),              {0x1, 0, 0, 0, REG_ECX}, 0x00008000},
> > > -	{FEAT_DEF(PCID),              {0x1, 0, 0, 0, REG_ECX}, 0x00020000},
> > > -	{FEAT_DEF(DCA),               {0x1, 0, 0, 0, REG_ECX}, 0x00040000},
> > > -	{FEAT_DEF(SSE4_1),            {0x1, 0, 0, 0, REG_ECX}, 0x00080000},
> > > -	{FEAT_DEF(SSE4_2),            {0x1, 0, 0, 0, REG_ECX}, 0x00100000},
> > > -	{FEAT_DEF(X2APIC),            {0x1, 0, 0, 0, REG_ECX}, 0x00200000},
> > > -	{FEAT_DEF(MOVBE),             {0x1, 0, 0, 0, REG_ECX}, 0x00400000},
> > > -	{FEAT_DEF(POPCNT),            {0x1, 0, 0, 0, REG_ECX}, 0x00800000},
> > > -	{FEAT_DEF(TSC_DEADLINE),      {0x1, 0, 0, 0, REG_ECX}, 0x01000000},
> > > -	{FEAT_DEF(AES),               {0x1, 0, 0, 0, REG_ECX}, 0x02000000},
> > > -	{FEAT_DEF(XSAVE),             {0x1, 0, 0, 0, REG_ECX}, 0x04000000},
> > > -	{FEAT_DEF(OSXSAVE),           {0x1, 0, 0, 0, REG_ECX}, 0x08000000},
> > > -	{FEAT_DEF(AVX),               {0x1, 0, 0, 0, REG_ECX}, 0x10000000},
> > > -	{FEAT_DEF(F16C),              {0x1, 0, 0, 0, REG_ECX}, 0x20000000},
> > > -	{FEAT_DEF(RDRAND),            {0x1, 0, 0, 0, REG_ECX}, 0x40000000},
> > > -
> > > -	{FEAT_DEF(FPU),               {0x1, 0, 0, 0, REG_EDX}, 0x00000001},
> > > -	{FEAT_DEF(VME),               {0x1, 0, 0, 0, REG_EDX}, 0x00000002},
> > > -	{FEAT_DEF(DE),                {0x1, 0, 0, 0, REG_EDX}, 0x00000004},
> > > -	{FEAT_DEF(PSE),               {0x1, 0, 0, 0, REG_EDX}, 0x00000008},
> > > -	{FEAT_DEF(TSC),               {0x1, 0, 0, 0, REG_EDX}, 0x00000010},
> > > -	{FEAT_DEF(MSR),               {0x1, 0, 0, 0, REG_EDX}, 0x00000020},
> > > -	{FEAT_DEF(PAE),               {0x1, 0, 0, 0, REG_EDX}, 0x00000040},
> > > -	{FEAT_DEF(MCE),               {0x1, 0, 0, 0, REG_EDX}, 0x00000080},
> > > -	{FEAT_DEF(CX8),               {0x1, 0, 0, 0, REG_EDX}, 0x00000100},
> > > -	{FEAT_DEF(APIC),              {0x1, 0, 0, 0, REG_EDX}, 0x00000200},
> > > -	{FEAT_DEF(SEP),               {0x1, 0, 0, 0, REG_EDX}, 0x00000800},
> > > -	{FEAT_DEF(MTRR),              {0x1, 0, 0, 0, REG_EDX}, 0x00001000},
> > > -	{FEAT_DEF(PGE),               {0x1, 0, 0, 0, REG_EDX}, 0x00002000},
> > > -	{FEAT_DEF(MCA),               {0x1, 0, 0, 0, REG_EDX}, 0x00004000},
> > > -	{FEAT_DEF(CMOV),              {0x1, 0, 0, 0, REG_EDX}, 0x00008000},
> > > -	{FEAT_DEF(PAT),               {0x1, 0, 0, 0, REG_EDX}, 0x00010000},
> > > -	{FEAT_DEF(PSE36),             {0x1, 0, 0, 0, REG_EDX}, 0x00020000},
> > > -	{FEAT_DEF(PSN),               {0x1, 0, 0, 0, REG_EDX}, 0x00040000},
> > > -	{FEAT_DEF(CLFSH),             {0x1, 0, 0, 0, REG_EDX}, 0x00080000},
> > > -	{FEAT_DEF(DS),                {0x1, 0, 0, 0, REG_EDX}, 0x00200000},
> > > -	{FEAT_DEF(ACPI),              {0x1, 0, 0, 0, REG_EDX}, 0x00400000},
> > > -	{FEAT_DEF(MMX),               {0x1, 0, 0, 0, REG_EDX}, 0x00800000},
> > > -	{FEAT_DEF(FXSR),              {0x1, 0, 0, 0, REG_EDX}, 0x01000000},
> > > -	{FEAT_DEF(SSE),               {0x1, 0, 0, 0, REG_EDX}, 0x02000000},
> > > -	{FEAT_DEF(SSE2),              {0x1, 0, 0, 0, REG_EDX}, 0x04000000},
> > > -	{FEAT_DEF(SS),                {0x1, 0, 0, 0, REG_EDX}, 0x08000000},
> > > -	{FEAT_DEF(HTT),               {0x1, 0, 0, 0, REG_EDX}, 0x10000000},
> > > -	{FEAT_DEF(TM),                {0x1, 0, 0, 0, REG_EDX}, 0x20000000},
> > > -	{FEAT_DEF(PBE),               {0x1, 0, 0, 0, REG_EDX}, 0x80000000},
> > > -
> > > -	{FEAT_DEF(DIGTEMP),           {0x6, 0, 0, 0, REG_EAX}, 0x00000001},
> > > -	{FEAT_DEF(TRBOBST),           {0x6, 0, 0, 0, REG_EAX}, 0x00000002},
> > > -	{FEAT_DEF(ARAT),              {0x6, 0, 0, 0, REG_EAX}, 0x00000004},
> > > -	{FEAT_DEF(PLN),               {0x6, 0, 0, 0, REG_EAX}, 0x00000010},
> > > -	{FEAT_DEF(ECMD),              {0x6, 0, 0, 0, REG_EAX}, 0x00000020},
> > > -	{FEAT_DEF(PTM),               {0x6, 0, 0, 0, REG_EAX}, 0x00000040},
> > > -
> > > -	{FEAT_DEF(MPERF_APERF_MSR),   {0x6, 0, 0, 0, REG_ECX}, 0x00000001},
> > > -	{FEAT_DEF(ACNT2),             {0x6, 0, 0, 0, REG_ECX}, 0x00000002},
> > > -	{FEAT_DEF(ENERGY_EFF),        {0x6, 0, 0, 0, REG_ECX}, 0x00000008},
> > > -
> > > -	{FEAT_DEF(FSGSBASE),          {0x7, 0, 0, 0, REG_EBX}, 0x00000001},
> > > -	{FEAT_DEF(BMI1),              {0x7, 0, 0, 0, REG_EBX}, 0x00000004},
> > > -	{FEAT_DEF(HLE),               {0x7, 0, 0, 0, REG_EBX}, 0x00000010},
> > > -	{FEAT_DEF(AVX2),              {0x7, 0, 0, 0, REG_EBX}, 0x00000020},
> > > -	{FEAT_DEF(SMEP),              {0x7, 0, 0, 0, REG_EBX}, 0x00000040},
> > > -	{FEAT_DEF(BMI2),              {0x7, 0, 0, 0, REG_EBX}, 0x00000080},
> > > -	{FEAT_DEF(ERMS),              {0x7, 0, 0, 0, REG_EBX}, 0x00000100},
> > > -	{FEAT_DEF(INVPCID),           {0x7, 0, 0, 0, REG_EBX}, 0x00000400},
> > > -	{FEAT_DEF(RTM),               {0x7, 0, 0, 0, REG_EBX}, 0x00000800},
> > > -
> > > -	{FEAT_DEF(LAHF_SAHF),  {0x80000001, 0, 0, 0, REG_ECX}, 0x00000001},
> > > -	{FEAT_DEF(LZCNT),      {0x80000001, 0, 0, 0, REG_ECX}, 0x00000010},
> > > -
> > > -	{FEAT_DEF(SYSCALL),    {0x80000001, 0, 0, 0, REG_EDX}, 0x00000800},
> > > -	{FEAT_DEF(XD),         {0x80000001, 0, 0, 0, REG_EDX}, 0x00100000},
> > > -	{FEAT_DEF(1GB_PG),     {0x80000001, 0, 0, 0, REG_EDX}, 0x04000000},
> > > -	{FEAT_DEF(RDTSCP),     {0x80000001, 0, 0, 0, REG_EDX}, 0x08000000},
> > > -	{FEAT_DEF(EM64T),      {0x80000001, 0, 0, 0, REG_EDX}, 0x20000000},
> > > -
> > > -	{FEAT_DEF(INVTSC),     {0x80000007, 0, 0, 0, REG_EDX}, 0x00000100},
> > > +	{FEAT_DEF(SSE3),		0x00000001, 0, REG_ECX,  0},
> > > +	{FEAT_DEF(PCLMULQDQ),		0x00000001, 0, REG_ECX,  1},
> > > +	{FEAT_DEF(DTES64),		0x00000001, 0, REG_ECX,  2},
> > > +	{FEAT_DEF(MONITOR),		0x00000001, 0, REG_ECX,  3},
> > > +	{FEAT_DEF(DS_CPL),		0x00000001, 0, REG_ECX,  4},
> > > +	{FEAT_DEF(VMX),			0x00000001, 0, REG_ECX,  5},
> > > +	{FEAT_DEF(SMX),			0x00000001, 0, REG_ECX,  6},
> > > +	{FEAT_DEF(EIST),		0x00000001, 0, REG_ECX,  7},
> > > +	{FEAT_DEF(TM2),			0x00000001, 0, REG_ECX,  8},
> > > +	{FEAT_DEF(SSSE3),		0x00000001, 0, REG_ECX,  9},
> > > +	{FEAT_DEF(CNXT_ID),		0x00000001, 0, REG_ECX, 10},
> > > +	{FEAT_DEF(FMA),			0x00000001, 0, REG_ECX, 12},
> > > +	{FEAT_DEF(CMPXCHG16B),		0x00000001, 0, REG_ECX, 13},
> > > +	{FEAT_DEF(XTPR),		0x00000001, 0, REG_ECX, 14},
> > > +	{FEAT_DEF(PDCM),		0x00000001, 0, REG_ECX, 15},
> > > +	{FEAT_DEF(PCID),		0x00000001, 0, REG_ECX, 17},
> > > +	{FEAT_DEF(DCA),			0x00000001, 0, REG_ECX, 18},
> > > +	{FEAT_DEF(SSE4_1),		0x00000001, 0, REG_ECX, 19},
> > > +	{FEAT_DEF(SSE4_2),		0x00000001, 0, REG_ECX, 20},
> > > +	{FEAT_DEF(X2APIC),		0x00000001, 0, REG_ECX, 21},
> > > +	{FEAT_DEF(MOVBE),		0x00000001, 0, REG_ECX, 22},
> > > +	{FEAT_DEF(POPCNT),		0x00000001, 0, REG_ECX, 23},
> > > +	{FEAT_DEF(TSC_DEADLINE),	0x00000001, 0, REG_ECX, 24},
> > > +	{FEAT_DEF(AES),			0x00000001, 0, REG_ECX, 25},
> > > +	{FEAT_DEF(XSAVE),		0x00000001, 0, REG_ECX, 26},
> > > +	{FEAT_DEF(OSXSAVE),		0x00000001, 0, REG_ECX, 27},
> > > +	{FEAT_DEF(AVX),			0x00000001, 0, REG_ECX, 28},
> > > +	{FEAT_DEF(F16C),		0x00000001, 0, REG_ECX, 29},
> > > +	{FEAT_DEF(RDRAND),		0x00000001, 0, REG_ECX, 30},
> > > +
> > > +	{FEAT_DEF(FPU),			0x00000001, 0, REG_EDX,  0},
> > > +	{FEAT_DEF(VME),			0x00000001, 0, REG_EDX,  1},
> > > +	{FEAT_DEF(DE),			0x00000001, 0, REG_EDX,  2},
> > > +	{FEAT_DEF(PSE),			0x00000001, 0, REG_EDX,  3},
> > > +	{FEAT_DEF(TSC),			0x00000001, 0, REG_EDX,  4},
> > > +	{FEAT_DEF(MSR),			0x00000001, 0, REG_EDX,  5},
> > > +	{FEAT_DEF(PAE),			0x00000001, 0, REG_EDX,  6},
> > > +	{FEAT_DEF(MCE),			0x00000001, 0, REG_EDX,  7},
> > > +	{FEAT_DEF(CX8),			0x00000001, 0, REG_EDX,  8},
> > > +	{FEAT_DEF(APIC),		0x00000001, 0, REG_EDX,  9},
> > > +	{FEAT_DEF(SEP),			0x00000001, 0, REG_EDX, 11},
> > > +	{FEAT_DEF(MTRR),		0x00000001, 0, REG_EDX, 12},
> > > +	{FEAT_DEF(PGE),			0x00000001, 0, REG_EDX, 13},
> > > +	{FEAT_DEF(MCA),			0x00000001, 0, REG_EDX, 14},
> > > +	{FEAT_DEF(CMOV),		0x00000001, 0, REG_EDX, 15},
> > > +	{FEAT_DEF(PAT),			0x00000001, 0, REG_EDX, 16},
> > > +	{FEAT_DEF(PSE36),		0x00000001, 0, REG_EDX, 17},
> > > +	{FEAT_DEF(PSN),			0x00000001, 0, REG_EDX, 18},
> > > +	{FEAT_DEF(CLFSH),		0x00000001, 0, REG_EDX, 19},
> > > +	{FEAT_DEF(DS),			0x00000001, 0, REG_EDX, 21},
> > > +	{FEAT_DEF(ACPI),		0x00000001, 0, REG_EDX, 22},
> > > +	{FEAT_DEF(MMX),			0x00000001, 0, REG_EDX, 23},
> > > +	{FEAT_DEF(FXSR),		0x00000001, 0, REG_EDX, 24},
> > > +	{FEAT_DEF(SSE),			0x00000001, 0, REG_EDX, 25},
> > > +	{FEAT_DEF(SSE2),		0x00000001, 0, REG_EDX, 26},
> > > +	{FEAT_DEF(SS),			0x00000001, 0, REG_EDX, 27},
> > > +	{FEAT_DEF(HTT),			0x00000001, 0, REG_EDX, 28},
> > > +	{FEAT_DEF(TM),			0x00000001, 0, REG_EDX, 29},
> > > +	{FEAT_DEF(PBE),			0x00000001, 0, REG_EDX, 31},
> > > +
> > > +	{FEAT_DEF(DIGTEMP),		0x00000006, 0, REG_EAX,  0},
> > > +	{FEAT_DEF(TRBOBST),		0x00000006, 0, REG_EAX,  1},
> > > +	{FEAT_DEF(ARAT),		0x00000006, 0, REG_EAX,  2},
> > > +	{FEAT_DEF(PLN),			0x00000006, 0, REG_EAX,  4},
> > > +	{FEAT_DEF(ECMD),		0x00000006, 0, REG_EAX,  5},
> > > +	{FEAT_DEF(PTM),			0x00000006, 0, REG_EAX,  6},
> > > +
> > > +	{FEAT_DEF(MPERF_APERF_MSR),	0x00000006, 0, REG_ECX,  0},
> > > +	{FEAT_DEF(ACNT2),		0x00000006, 0, REG_ECX,  1},
> > > +	{FEAT_DEF(ENERGY_EFF),		0x00000006, 0, REG_ECX,  3},
> > > +
> > > +	{FEAT_DEF(FSGSBASE),		0x00000007, 0, REG_EBX,  0},
> > > +	{FEAT_DEF(BMI1),		0x00000007, 0, REG_EBX,  2},
> > > +	{FEAT_DEF(HLE),			0x00000007, 0, REG_EBX,  4},
> > > +	{FEAT_DEF(AVX2),		0x00000007, 0, REG_EBX,  5},
> > > +	{FEAT_DEF(SMEP),		0x00000007, 0, REG_EBX,  6},
> > > +	{FEAT_DEF(BMI2),		0x00000007, 0, REG_EBX,  7},
> > > +	{FEAT_DEF(ERMS),		0x00000007, 0, REG_EBX,  8},
> > > +	{FEAT_DEF(INVPCID),		0x00000007, 0, REG_EBX, 10},
> > > +	{FEAT_DEF(RTM),			0x00000007, 0, REG_EBX, 11},
> > > +
> > > +	{FEAT_DEF(LAHF_SAHF),		0x80000001, 0, REG_ECX,  0},
> > > +	{FEAT_DEF(LZCNT),		0x80000001, 0, REG_ECX,  4},
> > > +
> > > +	{FEAT_DEF(SYSCALL),		0x80000001, 0, REG_EDX, 11},
> > > +	{FEAT_DEF(XD),			0x80000001, 0, REG_EDX, 20},
> > > +	{FEAT_DEF(1GB_PG),		0x80000001, 0, REG_EDX, 26},
> > > +	{FEAT_DEF(RDTSCP),		0x80000001, 0, REG_EDX, 27},
> > > +	{FEAT_DEF(EM64T),		0x80000001, 0, REG_EDX, 29},
> > > +
> > > +	{FEAT_DEF(INVTSC),		0x80000007, 0, REG_EDX,  8},
> > >  };
> > >  
> > >  /*
> > > @@ -187,51 +180,25 @@ static const struct feature_entry cpu_feature_table[] = {
> > >   * This function, when compiled with GCC, will generate architecture-neutral
> > >   * code, as per GCC manual.
> > >   */
> > > -static inline int
> > > -rte_cpu_get_features(struct cpuid_parameters_t params)
> > > +static inline void
> > > +rte_cpu_get_features(uint32_t leaf, uint32_t subleaf, cpuid_registers_t *out)
> > >  {
> > > -	int eax, ebx, ecx, edx;            /* registers */
> > > -
> > > -#ifndef __PIC__
> > > -   asm volatile ("cpuid"
> > > -                 /* output */
> > > -                 : "=a" (eax),
> > > -                   "=b" (ebx),
> > > -                   "=c" (ecx),
> > > -                   "=d" (edx)
> > > -                 /* input */
> > > -                 : "a" (params.eax),
> > > -                   "b" (params.ebx),
> > > -                   "c" (params.ecx),
> > > -                   "d" (params.edx));
> > > +#if defined(__i386__) && defined(__PIC__)
> > > +    /* %ebx is a forbidden register if we compile with -fPIC or -fPIE */
> > > +    asm volatile("movl %%ebx,%0 ; cpuid ; xchgl %%ebx,%0"
> > > +		 : "=r" (out[REG_EBX]),
> > > +		   "=a" (out[REG_EAX]),
> > > +		   "=c" (out[REG_ECX]),
> > > +		   "=d" (out[REG_EDX])
> > > +		 : "a" (leaf), "c" (subleaf));
> > >  #else
> > > -	asm volatile ( 
> > > -            "mov %%ebx, %%edi\n"
> > > -            "cpuid\n"
> > > -            "xchgl %%ebx, %%edi;\n"
> > > -            : "=a" (eax),
> > > -              "=D" (ebx),
> > > -              "=c" (ecx),
> > > -              "=d" (edx)
> > > -            /* input */
> > > -            : "a" (params.eax),
> > > -              "D" (params.ebx),
> > > -              "c" (params.ecx),
> > > -              "d" (params.edx));
> > > +    asm volatile("cpuid"
> > > +		 : "=b" (out[REG_EBX]),
> > > +		   "=a" (out[REG_EAX]),
> > > +		   "=c" (out[REG_ECX]),
> > > +		   "=d" (out[REG_EDX])
> > > +		 : "a" (leaf), "c" (subleaf));
This is throwing a compiler error:
dpdk/lib/librte_eal/common/eal_common_cpuflags.c:195:5: error: inconsistent
operand constraints in an ‘asm’

Pretty sure its because the cpuid_registers_t typdef is an array, so its passed
by reference already.  Looking into it.



> > >  #endif
> > > -
> > > -	switch (params.return_register) {
> > > -	case REG_EAX:
> > > -		return eax;
> > > -	case REG_EBX:
> > > -		return ebx;
> > > -	case REG_ECX:
> > > -		return ecx;
> > > -	case REG_EDX:
> > > -		return edx;
> > > -	default:
> > > -		return 0;
> > > -	}
> > >  }
> > >  
> > >  /*
> > > @@ -240,17 +207,20 @@ rte_cpu_get_features(struct cpuid_parameters_t params)
> > >  int
> > >  rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
> > >  {
> > > -	int value;
> > > +	const struct feature_entry *feat;
> > > +	cpu_registers_t regs;
This should be cpuid_registers_t.



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