[libvirt] [PATCH RFC 2/5] libxl: describe host cpu features based on hwcaps
Cedric Bosdonnat
cbosdonnat at suse.com
Mon Jul 11 08:46:00 UTC 2016
On Fri, 2016-07-08 at 17:16 +0100, Joao Martins wrote:
> Parse libxl_hwcaps accounting for versions for Xen 4.4.
> libxl_hwcaps is a set of cpuid leaves output that is described in [0] or
> [1] in Xen 4.7. This is a collection of CPUID leaves that are we version
> in libvirt whenever leaves are reordered or added. Thus we keep the
> common ones in one struct and others for each version. Since
> libxl_hwcaps doesn't appear to have a stable format across all supported
> versions thus we need to keep track of changes as a compromise whenever
> these extracting host featuresets are exported by libxl. Also we don't
> fail in initializing the driver in case parsing of hwcaps failed.
>
> xen/include/asm-x86/cpufeature.h
> include/public/arch-x86/cpufeatureset.h
>
> Signed-off-by: Joao Martins <joao.m.martins at oracle.com>
> ---
> Probably to make it easier to extend hwcaps handling in the future may
> be it's better to introduce an enum for the version and restructure this
> in another way?
> ---
> src/libxl/libxl_capabilities.c | 106 +++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 103 insertions(+), 3 deletions(-)
>
> diff --git a/src/libxl/libxl_capabilities.c b/src/libxl/libxl_capabilities.c
> index f71fd3b..c0857e5 100644
> --- a/src/libxl/libxl_capabilities.c
> +++ b/src/libxl/libxl_capabilities.c
> @@ -36,6 +36,8 @@
> #include "domain_capabilities.h"
> #include "vircommand.h"
> #include "libxl_capabilities.h"
> +#include "cpu/cpu_x86.h"
> +#include "cpu/cpu_x86_data.h"
>
>
> #define VIR_FROM_THIS VIR_FROM_LIBXL
> @@ -43,7 +45,8 @@
> VIR_LOG_INIT("libxl.libxl_capabilities");
>
> /* see xen-unstable.hg/xen/include/asm-x86/cpufeature.h */
> -#define LIBXL_X86_FEATURE_PAE_MASK 0x40
> +#define LIBXL_X86_FEATURE_PAE_MASK (1 << 6)
> +#define LIBXL_X86_FEATURE_LM_MASK (1 << 29)
+1 for the notation change: makes it much easier to associate to the
original bits definitions.
>
> struct guest_arch {
> @@ -57,17 +60,94 @@ struct guest_arch {
>
> #define XEN_CAP_REGEX "(xen|hvm)-[[:digit:]]+\\.[[:digit:]]+-(aarch64|armv7l|x86_32|x86_64|ia64|powerpc64)(p|be)?"
>
> +static int
> +libxlCapsAddCPUID(virCPUx86Data *data, virCPUx86CPUID *cpuid, ssize_t ncaps)
> +{
> + size_t i;
> +
> + for (i = 0; i < ncaps; i++) {
> + virCPUx86CPUID *c = &cpuid[i];
> +
> + if (virCPUx86DataAddCPUID(data, c) < 0) {
> + VIR_DEBUG("Failed to add CPUID(%x,%x)", c->eax_in, c->ecx_in);
> + return -1;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * The words represented in physinfo.hw_cap are host CPUID (sub) leafs.
> + * Position of these hasn't changed much up until Xen 4.7 with a rework
> + * on how CPUID is handled internally. As a side-effect it got normalized
> + * and also added more feature words. Although cannot be relied upon as
> + * stable interface, and hence we version changes in position of the features
> + * across all supported versions of the libxl driver until libxl exposes a
> + * stable representation of these capabilities. Fortunately not a lot of
> + * variation happened so it's still possible to keep track of these leafs
> + * to describe host CPU in libvirt capabilities. v0 is for Xen 4.4 up to 4.6,
> + * while v1 is meant for Xen 4.7, as depicted in the table below:
> + *
> + * | v0 (Xen 4.4 - 4.6) | v1 (Xen >= 4.7) |
> + * ---------------------------------------------
> + * word 0 | CPUID.00000001.EDX | CPUID.00000001.EDX |
> + * word 1 | CPUID.80000001.EDX | CPUID.00000001.ECX |
> + * word 2 | CPUID.80860001 | CPUID.80000001.EDX |
> + * word 3 | - Linux - | CPUID.80000001.ECX |
> + * word 4 | CPUID.00000001.ECX | CPUID.0000000D:1.EAX |
> + * word 5 | CPUID.C0000001 | CPUID.00000007:0.EBX |
> + * word 6 | CPUID.80000001.ECX | CPUID.00000007:0.ECX |
> + * word 7 | CPUID.00000007.EBX | CPUID.80000007.EDX |
> + * word 8 | - Non existent - | CPUID.80000008.EBX |
> + *
> + */
> +static virCPUDataPtr
> +libxlCapsNodeData(virCPUDefPtr cpu, libxl_hwcap hwcap, unsigned version)
> +{
> + ssize_t ncaps;
> + virCPUx86Data data = VIR_CPU_X86_DATA_INIT;
> + virCPUx86CPUID cpuid[] = {
> + { .eax_in = 0x00000001, .edx = hwcap[0] },
> + { .eax_in = 0x00000001, .ecx = (version > 0 ? hwcap[1] : hwcap[4]) },
Shouldn't constants be used rather than magic numbers for the versions?
How about something like LIBXL_HWCAP_V0?
Other than that, the patch looks good to me.
--
Cedric
> + { .eax_in = 0x80000001, .edx = (version > 0 ? hwcap[2] : hwcap[1]) },
> + { .eax_in = 0x80000001, .ecx = (version > 0 ? hwcap[3] : hwcap[6]) },
> + { .eax_in = 0x00000007, .ebx = (version > 0 ? hwcap[5] : hwcap[7]) }
> + };
> + virCPUx86CPUID cpuid_ver1[] = {
> + { .eax_in = 0x0000000D, .ecx_in = 1U, .eax = hwcap[4] },
> + { .eax_in = 0x00000007, .ecx_in = 0U, .ecx = hwcap[6] },
> + { .eax_in = 0x80000007, .ecx_in = 0U, .edx = hwcap[7] },
> + };
> +
> + ncaps = ARRAY_CARDINALITY(cpuid);
> + if (libxlCapsAddCPUID(&data, cpuid, ncaps) < 0)
> + return NULL;
> +
> + ncaps = ARRAY_CARDINALITY(cpuid_ver1);
> + if (version > 0 && libxlCapsAddCPUID(&data, cpuid_ver1, ncaps) < 0)
> + return NULL;
> +
> + return virCPUx86MakeData(cpu->arch, &data);
> +}
> +
> /* hw_caps is an array of 32-bit words whose meaning is listed in
> * xen-unstable.hg/xen/include/asm-x86/cpufeature.h. Each feature
> * is defined in the form X*32+Y, corresponding to the Y'th bit in
> * the X'th 32-bit word of hw_cap.
> */
> static int
> -libxlCapsInitCPU(virCapsPtr caps, libxl_physinfo *phy_info)
> +libxlCapsInitCPU(virCapsPtr caps, libxl_physinfo *phy_info, unsigned version)
> {
> virCPUDefPtr cpu = NULL;
> + virCPUDataPtr data = NULL;
> int ret = -1;
> int host_pae;
> + int host_lm;
> +
> + /* parse hw_cap only for x86 */
> + if (!phy_info->hw_cap[0])
> + return 0;
>
> if (VIR_ALLOC(cpu) < 0)
> goto error;
> @@ -77,15 +157,26 @@ libxlCapsInitCPU(virCapsPtr caps, libxl_physinfo *phy_info)
> virCapabilitiesAddHostFeature(caps, "pae") < 0)
> goto error;
>
> + host_lm = phy_info->hw_cap[version > 0 ? 2 : 1] & LIBXL_X86_FEATURE_LM_MASK;
> + if (host_lm)
> + cpu->arch = VIR_ARCH_X86_64;
> + else
> + cpu->arch = VIR_ARCH_I686;
> +
> cpu->type = VIR_CPU_TYPE_HOST;
> cpu->cores = phy_info->cores_per_socket;
> cpu->threads = phy_info->threads_per_core;
> cpu->sockets = phy_info->nr_cpus / (cpu->cores * cpu->threads);
> caps->host.cpu = cpu;
>
> + if (!(data = libxlCapsNodeData(cpu, phy_info->hw_cap, version))
> + || cpuDecode(cpu, data, NULL, 0, NULL) < 0)
> + goto cleanup;
> +
> ret = 0;
>
> cleanup:
> + cpuDataFree(data);
>
> return ret;
>
> @@ -97,7 +188,9 @@ libxlCapsInitCPU(virCapsPtr caps, libxl_physinfo *phy_info)
> static int
> libxlCapsInitHost(libxl_ctx *ctx, virCapsPtr caps)
> {
> + const libxl_version_info *ver_info;
> libxl_physinfo phy_info;
> + unsigned version;
>
> if (libxl_get_physinfo(ctx, &phy_info) != 0) {
> virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> @@ -105,8 +198,15 @@ libxlCapsInitHost(libxl_ctx *ctx, virCapsPtr caps)
> return -1;
> }
>
> - if (libxlCapsInitCPU(caps, &phy_info) < 0)
> + if ((ver_info = libxl_get_version_info(ctx)) == NULL) {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("Failed to get version info from libxenlight"));
> return -1;
> + }
> +
> + version = (ver_info->xen_version_minor >= 7);
> + if (libxlCapsInitCPU(caps, &phy_info, version) < 0)
> + VIR_WARN("Failed to initialize host cpu data");
>
> if (virCapabilitiesSetNetPrefix(caps, LIBXL_GENERATED_PREFIX_XEN) < 0)
> return -1;
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