Re: [Xen-devel] [PATCH v6 08/19] x86/VPMU: Add public xenpmu.h

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/20/2014 11:24 AM, Jan Beulich wrote:
> > --- /dev/null
> > +++ b/xen/include/public/arch-x86/pmu.h
> > @@ -0,0 +1,62 @@
> > +#ifndef __XEN_PUBLIC_ARCH_X86_PMU_H__
> > +#define __XEN_PUBLIC_ARCH_X86_PMU_H__
> > +
> > +/* x86-specific PMU definitions */
> > +
> > +/* AMD PMU registers and structures */
> > +struct xen_pmu_amd_ctxt {
> > +    uint32_t counters;       /* Offset to counter MSRs */
> > +    uint32_t ctrls;          /* Offset to control MSRs */
> > +};
> > +
> > +/* Intel PMU registers and structures */
> > +struct xen_pmu_cntr_pair {
> > +    uint64_t counter;
> > +    uint64_t control;
> > +};
> > +
> > +struct xen_pmu_intel_ctxt {
> > +    uint64_t global_ctrl;
> > +    uint64_t global_ovf_ctrl;
> > +    uint64_t global_status;
> > +    uint64_t fixed_ctrl;
> > +    uint64_t ds_area;
> > +    uint64_t pebs_enable;
> > +    uint64_t debugctl;
> > +    uint32_t fixed_counters;  /* Offset to fixed counter MSRs */
> > +    uint32_t arch_counters;   /* Offset to architectural counter MSRs */
> > +};
> > +
> > +#define XENPMU_MAX_CTXT_SZ        (sizeof(struct xen_pmu_amd_ctxt) > \
> > +                                    sizeof(struct xen_pmu_intel_ctxt) ? \
> > +                                     sizeof(struct xen_pmu_amd_ctxt) : \
> > +                                     sizeof(struct xen_pmu_intel_ctxt))
> > +#define XENPMU_CTXT_PAD_SZ        (((XENPMU_MAX_CTXT_SZ + 64) & ~63) + 128)
> Is this really usefully derived from XENPMU_MAX_CTXT_SZ? I.e. is it
> okay for this value to change when one of the structures grows big
> enough? I would have thought that the padding below is to fix the
> size of the structure once and for all (and if that's right, I suppose
> a respective BUILD_BUG_ON() would be quite desirable).

Yes, the way XENPMU_CTXT_PAD_SZ is calculated is wrong, it should be a 
fixed value, not derived from arch-specific structures sizes.

> > --- /dev/null
> > +++ b/xen/include/public/pmu.h
> > @@ -0,0 +1,38 @@
> > +#ifndef __XEN_PUBLIC_PMU_H__
> > +#define __XEN_PUBLIC_PMU_H__
> > +
> > +#include "xen.h"
> > +#if defined(__i386__) || defined(__x86_64__)
> > +#include "arch-x86/pmu.h"
> > +#elif defined (__arm__) || defined (__aarch64__)
> > +#include "arch-arm.h"
> > +#else
> > +#error "Unsupported architecture"
> > +#endif
> > +
> > +#define XENPMU_VER_MAJ    0
> > +#define XENPMU_VER_MIN    0
> Do you really want to start at 0.0?
Right, I'll start with 0.1

-boris

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