From: Bharata B Rao <bharata@linux.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powerpc/book3s64/radix: Add kernel command line option to disable radix GTSE
Date: Mon, 27 Jul 2020 17:06:24 +0530 [thread overview]
Message-ID: <20200727113624.GA1439452@in.ibm.com> (raw)
In-Reply-To: <20200727085908.420806-1-aneesh.kumar@linux.ibm.com>
On Mon, Jul 27, 2020 at 02:29:08PM +0530, Aneesh Kumar K.V wrote:
> This adds a kernel command line option that can be used to disable GTSE support.
> Disabling GTSE implies kernel will make hcalls to invalidate TLB entries.
>
> This was done so that we can do VM migration between configs that enable/disable
> GTSE support via hypervisor. To migrate a VM from a system that supports
> GTSE to a system that doesn't, we can boot the guest with
> radix_hcall_invalidate=on, thereby forcing the guest to use hcalls for TLB
> invalidates.
>
> The check for hcall availability is done in pSeries_setup_arch so that
> the panic message appears on the console. This should only happen on
> a hypervisor that doesn't force the guest to hash translation even
> though it can't handle the radix GTSE=0 request via CAS. With
> radix_hcall_invalidate=on if the hypervisor doesn't support hcall_rpt_invalidate
> hcall it should force the LPAR to hash translation.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested
1. radix_hcall_invalidate=on with KVM implementation of H_RPT_INVALIDATE hcall,
the tlb flush calls get off-loaded to the hcall.
2. radix_hcall_invalidate=on w/o H_RPT_INVALIDATE hcall, the guest kernel
panics as per design.
Tested-by: Bharata B Rao <bharata@linux.ibm.com>
next prev parent reply other threads:[~2020-07-27 11:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 8:59 [PATCH v2] powerpc/book3s64/radix: Add kernel command line option to disable radix GTSE Aneesh Kumar K.V
2020-07-27 11:36 ` Bharata B Rao [this message]
2020-07-30 12:50 ` Michael Ellerman
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