Re: expose host CPU features to guests

Anthony Liguori
2007-09-05T19:26:11Z

On Wed, 2007-09-05 at 20:45 +0300, danken-atKUWr5tajBWk0Htik3J/w@public.gmane.org wrote:
> Hi,
>
> It's a pity not to use a host CPU feature if it is available. This patch
> exposes host CPU features to guests. It allows fine-tuning the presented
> features from the command-line.
>
> The code could use some serious clean ups, but I think it is interesting
> enough right now. I'd be happy to hear your opinion and suggestions.
> The diff are done against qemu cvs. I tried it with kvm, but I thinkg it
> should be useful also for kqemu.

I like this idea but I have some suggestions about the general approach.
I think instead of defining another machine type, it would be better to
just have a command line option like -cpuid that took a comma separate
string of features with "all" meaning all features that the host has.

I also think it would be nicer to use cpuid() directly instead of
attempting to parse /proc/cpuinfo.

Regards,

Anthony Liguori

> Regards,
>
> Dan.
>
> Index: vl.c
> ===================================================================
> RCS file: /sources/qemu/qemu/vl.c,v
> retrieving revision 1.336
> diff -u -p -r1.336 vl.c
> --- vl.c 28 Aug 2007 22:21:40 -0000 1.336
> +++ vl.c 5 Sep 2007 15:48:10 -0000
> @@ -6575,12 +6575,24 @@ int qemu_register_machine(QEMUMachine *m
> return 0;
> }
>
> +const char *machine_flavor = 0;
> +
> QEMUMachine *find_machine(const char *name)
> {
> QEMUMachine *m;
>
> + int n;
> + machine_flavor = strchr(name, ',');
> + if (machine_flavor) {
> + n = machine_flavor - name;
> + machine_flavor++;
> + } else {
> + n = strlen(name);
> + machine_flavor = "";
> + }
> +
> for(m = first_machine; m != NULL; m = m->next) {
> - if (!strcmp(m->name, name))
> + if (!strncmp(m->name, name, n))
> return m;
> }
> return NULL;
> @@ -7343,6 +7355,7 @@ static void read_passwords(void)
> void register_machines(void)
> {
> #if defined(TARGET_I386)
> + qemu_register_machine(&host_pc_machine);
> qemu_register_machine(&pc_machine);
> qemu_register_machine(&isapc_machine);
> #elif defined(TARGET_PPC)
> Index: vl.h
> ===================================================================
> RCS file: /sources/qemu/qemu/vl.h,v
> retrieving revision 1.264
> diff -u -p -r1.264 vl.h
> --- vl.h 26 Aug 2007 17:46:00 -0000 1.264
> +++ vl.h 5 Sep 2007 15:48:10 -0000
> @@ -1156,6 +1156,7 @@ void piix4_smbus_register_device(SMBusDe
> void acpi_bios_init(void);
>
> /* pc.c */
> +extern QEMUMachine host_pc_machine;
> extern QEMUMachine pc_machine;
> extern QEMUMachine isapc_machine;
> extern int fd_bootchk;
> Index: hw/pc.c
> ===================================================================
> RCS file: /sources/qemu/qemu/hw/pc.c,v
> retrieving revision 1.83
> diff -u -p -r1.83 pc.c
> --- hw/pc.c 26 Aug 2007 17:51:39 -0000 1.83
> +++ hw/pc.c 5 Sep 2007 15:48:10 -0000
> @@ -965,6 +965,28 @@ static void pc_init_isa(int ram_size, in
> initrd_filename, 0);
> }
>
> +int use_hostlike_cpu = 0;
> +
> +static void pc_init_hostlike(ram_addr_t ram_size, int vga_ram_size, int boot_device,
> + DisplayState *ds, const char **fd_filename,
> + int snapshot,
> + const char *kernel_filename,
> + const char *kernel_cmdline,
> + const char *initrd_filename)
> +{
> + use_hostlike_cpu = 1;
> + pc_init1(ram_size, vga_ram_size, boot_device,
> + ds, fd_filename, snapshot,
> + kernel_filename, kernel_cmdline,
> + initrd_filename, 1);
> +}
> +
> +QEMUMachine host_pc_machine = {
> + "host",
> + "Standard PC with host-like CPU",
> + pc_init_hostlike,
> +};
> +
> QEMUMachine pc_machine = {
> "pc",
> "Standard PC",
> Index: target-i386/cpu.h
> ===================================================================
> RCS file: /sources/qemu/qemu/target-i386/cpu.h,v
> retrieving revision 1.45
> diff -u -p -r1.45 cpu.h
> --- target-i386/cpu.h 11 Jul 2007 22:48:58 -0000 1.45
> +++ target-i386/cpu.h 5 Sep 2007 15:48:10 -0000
> @@ -267,21 +267,44 @@
> #define CPUID_CMOV (1 << 15)
> #define CPUID_PAT (1 << 16)
> #define CPUID_PSE36 (1 << 17)
> +#define CPUID_PN (1 << 18)
> #define CPUID_CLFLUSH (1 << 19)
> -/* ... */
> +#define CPUID_DTS (1 << 21)
> +#define CPUID_ACPI (1 << 22)
> #define CPUID_MMX (1 << 23)
> #define CPUID_FXSR (1 << 24)
> #define CPUID_SSE (1 << 25)
> #define CPUID_SSE2 (1 << 26)
> +#define CPUID_SS (1 << 27)
> +#define CPUID_HT (1 << 28)
> +#define CPUID_TM (1 << 29)
> +#define CPUID_IA64 (1 << 30)
> +#define CPUID_PBE (1 << 31)
>
> #define CPUID_EXT_SSE3 (1 << 0)
> #define CPUID_EXT_MONITOR (1 << 3)
> +#define CPUID_EXT_DSCPL (1 << 4)
> +#define CPUID_EXT_VMX (1 << 5)
> +#define CPUID_EXT_SMX (1 << 6)
> +#define CPUID_EXT_EST (1 << 7)
> +#define CPUID_EXT_TM2 (1 << 8)
> +#define CPUID_EXT_SSSE3 (1 << 9)
> +#define CPUID_EXT_CID (1 << 10)
> #define CPUID_EXT_CX16 (1 << 13)
> +#define CPUID_EXT_XTPR (1 << 14)
> +#define CPUID_EXT_DCA (1 << 17)
> +#define CPUID_EXT_POPCNT (1 << 22)
>
> #define CPUID_EXT2_SYSCALL (1 << 11)
> +#define CPUID_EXT2_MP (1 << 19)
> #define CPUID_EXT2_NX (1 << 20)
> +#define CPUID_EXT2_MMXEXT (1 << 22)
> #define CPUID_EXT2_FFXSR (1 << 25)
> +#define CPUID_EXT2_PDPE1GB (1 << 26)
> +#define CPUID_EXT2_RDTSCP (1 << 27)
> #define CPUID_EXT2_LM (1 << 29)
> +#define CPUID_EXT2_3DNOWEXT (1 << 30)
> +#define CPUID_EXT2_3DNOW (1 << 31)
>
> #define EXCP00_DIVZ 0
> #define EXCP01_SSTP 1
> Index: target-i386/helper2.c
> ===================================================================
> RCS file: /sources/qemu/qemu/target-i386/helper2.c,v
> retrieving revision 1.48
> diff -u -p -r1.48 helper2.c
> --- target-i386/helper2.c 31 Jul 2007 23:09:18 -0000 1.48
> +++ target-i386/helper2.c 5 Sep 2007 15:48:10 -0000
> @@ -45,6 +45,272 @@ int modify_ldt(int func, void *ptr, unsi
> #endif
> #endif /* USE_CODE_COPY */
>
> +/* x86_cap_flags taken from Linux's arch/i386/kernel/cpu/proc.c */
> +static const char * const x86_cap_flags[] = {
> + /* Intel-defined */
> + "fpu", "vme", "de", "pse", "tsc", "msr", "pae", "mce",
> + "cx8", "apic", NULL, "sep", "mtrr", "pge", "mca", "cmov",
> + "pat", "pse36", "pn", "clflush", NULL, "dts", "acpi", "mmx",
> + "fxsr", "sse", "sse2", "ss", "ht", "tm", "ia64", "pbe",
> +
> + /* AMD-defined */
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, "syscall", NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, "mp", "nx", NULL, "mmxext", NULL,
> + NULL, "fxsr_opt", "pdpe1gb", "rdtscp", NULL, "lm", "3dnowext", "3dnow",
> +
> + /* Transmeta-defined */
> + "recovery", "longrun", NULL, "lrti", NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> +
> + /* Other (Linux-defined) */
> + "cxmmx", "k6_mtrr", "cyrix_arr", "centaur_mcr",
> + NULL, NULL, NULL, NULL,
> + "constant_tsc", "up", NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> +
> + /* Intel-defined (#2) */
> + "pni", NULL, NULL, "monitor", "ds_cpl", "vmx", "smx", "est",
> + "tm2", "ssse3", "cid", NULL, NULL, "cx16", "xtpr", NULL,
> + NULL, NULL, "dca", NULL, NULL, NULL, NULL, "popcnt",
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> +
> + /* VIA/Cyrix/Centaur-defined */
> + NULL, NULL, "rng", "rng_en", NULL, NULL, "ace", "ace_en",
> + "ace2", "ace2_en", "phe", "phe_en", "pmm", "pmm_en", NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> +
> + /* AMD-defined (#2) */
> + "lahf_lm", "cmp_legacy", "svm", "extapic", "cr8legacy", "abm",
> + "sse4a", "misalignsse",
> + "3dnowprefetch", "osvw", "ibs", NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
> +};
> +
> +void add_flagname_to_bitmaps(char *flagname, int *features, int *ext_features, int *ext2_features)
> +{
> + int i;
> + for ( i = 0 ; i < 32 ; i++ )
> + if (x86_cap_flags[i] && !strcmp (flagname, x86_cap_flags[i])) {
> + *features |= 1 << i;
> + return;
> + }
> + for ( i = 0 ; i < 32 ; i++ )
> + if (x86_cap_flags[32*4+i] && !strcmp (flagname, x86_cap_flags[32*4+i])) {
> + *ext_features |= 1 << i;
> + return;
> + }
> + for ( i = 0 ; i < 32 ; i++ )
> + if (x86_cap_flags[32*1+i] && !strcmp (flagname, x86_cap_flags[32*1+i])) {
> + *ext2_features |= 1 << i;
> + return;
> + }
> + /* Silently ignore Linux-defined features */
> + for ( i = 0 ; i < 32 ; i++ )
> + if (x86_cap_flags[32*3+i] && !strcmp (flagname, x86_cap_flags[32*3+i])) {
> + return;
> + }
> + fprintf(stderr, "CPU feature %s not found\n", flagname);
> +}
> +
> +static void apply_machine_flavor(CPUX86State *env)
> +{
> + int plus_features = 0, plus_ext_features = 0, plus_ext2_features = 0;
> + int minus_features = 0, minus_ext_features = 0, minus_ext2_features = 0;
> + int family = -1, model = -1, stepping = -1;
> +
> + extern char *machine_flavor;
> + char *s = strdup(machine_flavor);
> + char *featurestr = strtok(s, ",");
> +
> + while (featurestr) {
> + char *val;
> + if (featurestr[0] == '+') {
> + add_flagname_to_bitmaps(featurestr + 1, &plus_features, &plus_ext_features, &plus_ext2_features);
> + }
> + else if (featurestr[0] == '-') {
> + add_flagname_to_bitmaps(featurestr + 1, &minus_features, &minus_ext_features, &minus_ext2_features);
> + }
> + else if ((val = strchr(featurestr, '='))) {
> + *val = 0; val++;
> + if (!strcmp(featurestr, "family")) {
> + family = atoi(val);
> + if (family <= 0) {
> + fprintf(stderr, "bad numerical value %s\n", val);
> + exit(1);
> + }
> + env->cpuid_version &= 0xFF;
> + env->cpuid_version |= (family << 8);
> + } else if (!strcmp(featurestr, "model")) {
> + model = atoi(val);
> + if (model <= 0) {
> + fprintf(stderr, "bad numerical value %s\n", val);
> + exit(1);
> + }
> + env->cpuid_version &= 0xFFFFFF0F;
> + env->cpuid_version |= (model << 4);
> + } else if (!strcmp(featurestr, "stepping")) {
> + stepping = atoi(val);
> + if (stepping <= 0) {
> + fprintf(stderr, "bad numerical value %s\n", val);
> + exit(1);
> + }
> + env->cpuid_version &= 0xFFFFFFF0;
> + env->cpuid_version |= stepping;
> + } else {
> + fprintf(stderr, "unknown feature %s\n", featurestr);
> + exit(1);
> + }
> + } else {
> + fprintf(stderr, "feature string `%s' not in format (+feature|-feature|feature=xyz)\n", featurestr);
> + exit(1);
> + }
> + featurestr = strtok(NULL, ",");
> + }
> + free(s);
> + env->cpuid_features |= plus_features;
> + env->cpuid_ext_features |= plus_ext_features;
> + env->cpuid_ext2_features |= plus_ext2_features;
> + env->cpuid_features &= ~minus_features;
> + env->cpuid_ext_features &= ~minus_ext_features;
> + env->cpuid_ext2_features &= ~minus_ext2_features;
> +}
> +
> +static int read_one_cpu_info(CPUX86State *env, FILE *f)
> +{
> + char line[300], *val;
> + char vendor_id[13];
> + int family = -1, model = -1, stepping = -1;
> + int features = 0, ext_features = 0, ext2_features = 0;
> +
> + while (fgets(line, sizeof(line), f)) {
> + if (!strtok(line, "\t") || line[0]=='\n') {
> + break;
> + }
> + val = strtok(NULL, "\t:");
> + if (!val)
> + val = "";
> + if (*val==' ')
> + val++;
> +
> + if (!strcmp(line,"vendor_id")) {
> + strncpy(vendor_id, val, sizeof(vendor_id) - 1);
> + vendor_id[sizeof(vendor_id)-1] = 0;
> + }
> + if (!strcmp(line,"cpu family")) {
> + family = atoi(val);
> + }
> + if (!strcmp(line,"model")) {
> + model = atoi(val);
> + }
> + if (!strcmp(line,"stepping")) {
> + stepping = atoi(val);
> + }
> + if (!strcmp(line,"flags")) {
> + char *flagname;
> + struct flagstorage {
> + char *name;
> + int bit;
> + int *container;
> + };
> +
> + flagname = strtok(val, " ");
> + while (flagname) {
> + add_flagname_to_bitmaps(flagname, &features, &ext_features, &ext2_features);
> + flagname = strtok(NULL, " \n");
> + }
> + features &= ~CPUID_ACPI; /* acpi causes guest kernel panic on boot time, in cpu_identify */
> + ext_features &= ~CPUID_EXT_VMX; /* KVM is not recursive */
> + }
> + }
> + if (family==-1 || model==-1 || stepping==-1)
> + return -1;
> + env->cpuid_level = 2;
> + env->cpuid_vendor1 = *(uint32_t *)&vendor_id[0];
> + env->cpuid_vendor2 = *(uint32_t *)&vendor_id[4];
> + env->cpuid_vendor3 = *(uint32_t *)&vendor_id[8];
> + env->cpuid_version = (family << 8) | (model << 4) | stepping;
> + env->cpuid_features = features;
> + env->cpuid_ext_features = ext_features;
> + env->cpuid_ext2_features = ext2_features;
> + env->pat = 0x0007040600070406ULL;
> + /* TODO expose real cpuid extended level */
> +#ifdef TARGET_X86_64
> + env->cpuid_xlevel = 0x80000008;
> +#else
> + env->cpuid_xlevel = 0;
> +#endif
> + return 0;
> +}
> +
> +static int set_guest_cpu_hostlike(CPUX86State *env) {
> + FILE *f;
> + f = fopen("/proc/cpuinfo", "r");
> + if (!f) {
> + fprintf(stderr, "falling back to standard guest cpu\n");
> + return -1;
> + }
> + read_one_cpu_info(env, f);
> + fclose(f);
> + return 0;
> +}
> +
> +static int set_guest_cpu_standard(CPUX86State *env)
> +{
> + int family, model, stepping;
> +#ifdef TARGET_X86_64
> + env->cpuid_vendor1 = 0x68747541; /* "Auth" */
> + env->cpuid_vendor2 = 0x69746e65; /* "enti" */
> + env->cpuid_vendor3 = 0x444d4163; /* "cAMD" */
> + family = 6;
> + model = 2;
> + stepping = 3;
> +#else
> + env->cpuid_vendor1 = 0x756e6547; /* "Genu" */
> + env->cpuid_vendor2 = 0x49656e69; /* "ineI" */
> + env->cpuid_vendor3 = 0x6c65746e; /* "ntel" */
> +#if 0
> + /* pentium 75-200 */
> + family = 5;
> + model = 2;
> + stepping = 11;
> +#else
> + /* pentium pro */
> + family = 6;
> + model = 3;
> + stepping = 3;
> +#endif
> +#endif
> + env->cpuid_level = 2;
> + env->cpuid_version = (family << 8) | (model << 4) | stepping;
> + env->cpuid_features = (CPUID_FP87 | CPUID_DE | CPUID_PSE |
> + CPUID_TSC | CPUID_MSR | CPUID_MCE |
> + CPUID_CX8 | CPUID_PGE | CPUID_CMOV |
> + CPUID_PAT);
> + env->pat = 0x0007040600070406ULL;
> + env->cpuid_ext_features = CPUID_EXT_SSE3;
> + env->cpuid_features |= CPUID_FXSR | CPUID_MMX | CPUID_SSE | CPUID_SSE2 | CPUID_PAE | CPUID_SEP;
> + env->cpuid_features |= CPUID_APIC;
> + env->cpuid_xlevel = 0;
> +#ifdef TARGET_X86_64
> + /* currently not enabled for std i386 because not fully tested */
> + env->cpuid_ext2_features = (env->cpuid_features & 0x0183F3FF);
> + env->cpuid_ext2_features |= CPUID_EXT2_LM | CPUID_EXT2_SYSCALL | CPUID_EXT2_NX;
> + env->cpuid_xlevel = 0x80000008;
> +
> + /* these features are needed for Win64 and aren't fully implemented */
> + env->cpuid_features |= CPUID_MTRR | CPUID_CLFLUSH | CPUID_MCA;
> + /* this feature is needed for Solaris and isn't fully implemented */
> + env->cpuid_features |= CPUID_PSE36;
> +#endif
> + return 0;
> +}
> +
> CPUX86State *cpu_x86_init(void)
> {
> CPUX86State *env;
> @@ -80,64 +346,23 @@ CPUX86State *cpu_x86_init(void)
> }
> #endif
> {
> - int family, model, stepping;
> -#ifdef TARGET_X86_64
> - env->cpuid_vendor1 = 0x68747541; /* "Auth" */
> - env->cpuid_vendor2 = 0x69746e65; /* "enti" */
> - env->cpuid_vendor3 = 0x444d4163; /* "cAMD" */
> - family = 6;
> - model = 2;
> - stepping = 3;
> -#else
> - env->cpuid_vendor1 = 0x756e6547; /* "Genu" */
> - env->cpuid_vendor2 = 0x49656e69; /* "ineI" */
> - env->cpuid_vendor3 = 0x6c65746e; /* "ntel" */
> -#if 0
> - /* pentium 75-200 */
> - family = 5;
> - model = 2;
> - stepping = 11;
> -#else
> - /* pentium pro */
> - family = 6;
> - model = 3;
> - stepping = 3;
> -#endif
> -#endif
> - env->cpuid_level = 2;
> - env->cpuid_version = (family << 8) | (model << 4) | stepping;
> - env->cpuid_features = (CPUID_FP87 | CPUID_DE | CPUID_PSE |
> - CPUID_TSC | CPUID_MSR | CPUID_MCE |
> - CPUID_CX8 | CPUID_PGE | CPUID_CMOV |
> - CPUID_PAT);
> - env->pat = 0x0007040600070406ULL;
> - env->cpuid_ext_features = CPUID_EXT_SSE3;
> - env->cpuid_features |= CPUID_FXSR | CPUID_MMX | CPUID_SSE | CPUID_SSE2 | CPUID_PAE | CPUID_SEP;
> - env->cpuid_features |= CPUID_APIC;
> - env->cpuid_xlevel = 0;
> - {
> - const char *model_id = "QEMU Virtual CPU version " QEMU_VERSION;
> - int c, len, i;
> - len = strlen(model_id);
> - for(i = 0; i < 48; i++) {
> - if (i >= len)
> - c = '\0';
> - else
> - c = model_id[i];
> - env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
> - }
> + extern int use_hostlike_cpu;
> + if (!use_hostlike_cpu || set_guest_cpu_hostlike(env))
> + set_guest_cpu_standard(env);
> + apply_machine_flavor(env);
> + }
> + {
> + const char *model_id = "QEMU Virtual CPU version " QEMU_VERSION;
> + int c, len, i;
> +
> + len = strlen(model_id);
> + for(i = 0; i < 48; i++) {
> + if (i >= len)
> + c = '\0';
> + else
> + c = model_id[i];
> + env->cpuid_model[i >> 2] |= c << (8 * (i & 3));
> }
> -#ifdef TARGET_X86_64
> - /* currently not enabled for std i386 because not fully tested */
> - env->cpuid_ext2_features = (env->cpuid_features & 0x0183F3FF);
> - env->cpuid_ext2_features |= CPUID_EXT2_LM | CPUID_EXT2_SYSCALL | CPUID_EXT2_NX;
> - env->cpuid_xlevel = 0x80000008;
> -
> - /* these features are needed for Win64 and aren't fully implemented */
> - env->cpuid_features |= CPUID_MTRR | CPUID_CLFLUSH | CPUID_MCA;
> - /* this feature is needed for Solaris and isn't fully implemented */
> - env->cpuid_features |= CPUID_PSE36;
> -#endif
> }
> cpu_reset(env);
> #ifdef USE_KQEMU
>
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