[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen: Add command line option to enable ASID support -- on by default
On 07/03/2012 18:14, "George Dunlap" <george.dunlap@xxxxxxxxxx> wrote: > On Wed, 2012-03-07 at 18:07 +0000, Keir Fraser wrote: >> On 07/03/2012 17:58, "George Dunlap" <george.dunlap@xxxxxxxxxxxxx> wrote: >> >>> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> >> >> Why would you want to be able to disable the feature? > > Well at very least to measure the performance benefit (or overhead) of > using the feature. There may be hardware in the future where ASIDs may > cause problems; who knows. > > AFAICT this isn't documented anywhere, so if you really don't want Yet > Another Option, we could probably get rid of it from the XenServer > patchqueue. But I didn't see any harm in it; and you never know when > the flexibility of disabling something without recompiling will come in > handy. Okay, I applied it. I also moved the implementation into hvm/asid.c by the way -- your patch was unnecessarily AMD-specific. xen-unstable:24986 -- Keir > -George > >> >> -- Keir >> >>> diff --git a/xen/arch/x86/hvm/svm/asid.c b/xen/arch/x86/hvm/svm/asid.c >>> --- a/xen/arch/x86/hvm/svm/asid.c >>> +++ b/xen/arch/x86/hvm/svm/asid.c >>> @@ -24,12 +24,16 @@ >>> #include <asm/amd.h> >>> #include <asm/hvm/nestedhvm.h> >>> >>> +/* Xen command-line option to enable ASIDs */ >>> +static int opt_asid_enabled = 1; >>> +boolean_param("asid", opt_asid_enabled); >>> + >>> void svm_asid_init(struct cpuinfo_x86 *c) >>> { >>> int nasids = 0; >>> >>> /* Check for erratum #170, and leave ASIDs disabled if it's present. */ >>> - if ( !cpu_has_amd_erratum(c, AMD_ERRATUM_170) ) >>> + if ( opt_asid_enabled && !cpu_has_amd_erratum(c, AMD_ERRATUM_170) ) >>> nasids = cpuid_ebx(0x8000000A); >>> >>> hvm_asid_init(nasids); >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@xxxxxxxxxxxxx >>> http://lists.xen.org/xen-devel >> >> > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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