From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Jonathan Corbet <corbet@lwn.net>,
Peter Zijlstra <peterz@infradead.org>,
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Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
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Viresh Kumar <viresh.kumar@linaro.org>,
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Subject: Re: [PATCH 4/4] x86/tsx: Add cmdline tsx=fake to not clear CPUID bits RTM and HLE
Date: Tue, 6 Jul 2021 15:51:27 -0700 [thread overview]
Message-ID: <20210706225127.kyn7amrln6ydfcig@gupta-dev2.localdomain> (raw)
In-Reply-To: <CAOpTY_pmNah_OCzk3XRyTsgkCPdJD1tp2RxKHMieFQM1s-tQNA@mail.gmail.com>
On 06.07.2021 17:19, Eduardo Habkost wrote:
>On Tue, Jul 6, 2021 at 5:15 PM Pawan Gupta
><pawan.kumar.gupta@linux.intel.com> wrote:
>>
>> On 06.07.2021 15:52, Eduardo Habkost wrote:
>> >On Wed, Jun 09, 2021 at 02:14:39PM -0700, Pawan Gupta wrote:
>> >> On CPUs that deprecated TSX, clearing the enumeration bits CPUID.RTM and
>> >> CPUID.HLE may not be desirable in some corner cases. Like a saved guest
>> >> would refuse to resume if it was saved before the microcode update
>> >> that deprecated TSX.
>> >
>> >Why is a global option necessary to allow those guests to be
>> >resumed? Why can't KVM_GET_SUPPORTED_CPUID always return the HLE
>> >and RTM bits as supported when the host CPU has them?
>>
>> Yes, the global option is unnecessary and this patch was dropped in v2.
>
>Was the behaviour this patch originally tried to fix changed in v2 as
>well? Is it going to be possible to resume a HLE=1,RTM=1 VM on a
>TSX_FORCE_ABORT=1 host with no extra kernel command line options
>needed?
The problem it tried to solve is still present, but the global switch
was thought to be unnecessary. I see that Paolo has some suggestions to
fix this in the userspace.
Thanks,
Pawan
prev parent reply other threads:[~2021-07-06 22:51 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 20:57 [PATCH 0/4] TSX force abort Pawan Gupta
2021-06-09 20:58 ` [PATCH 1/4] x86/msr: Define new bits in TSX_FORCE_ABORT MSR Pawan Gupta
2021-06-11 8:39 ` Borislav Petkov
2021-06-11 21:31 ` Pawan Gupta
2021-06-09 21:12 ` [PATCH 2/4] perf/x86/intel: Do not deploy workaround when TSX is deprecated Pawan Gupta
2021-06-11 7:50 ` Borislav Petkov
2021-06-11 21:34 ` Pawan Gupta
2021-06-11 22:01 ` Borislav Petkov
2021-06-11 23:21 ` Pawan Gupta
2021-06-09 21:13 ` [PATCH 3/4] x86/tsx: Clear CPUID bits when TSX always force aborts Pawan Gupta
2021-06-11 10:03 ` Borislav Petkov
2021-06-11 21:36 ` Pawan Gupta
2021-06-09 21:14 ` [PATCH 4/4] x86/tsx: Add cmdline tsx=fake to not clear CPUID bits RTM and HLE Pawan Gupta
2021-06-11 10:06 ` Borislav Petkov
2021-06-11 21:37 ` Pawan Gupta
2021-07-06 19:52 ` Eduardo Habkost
2021-07-06 21:05 ` Paolo Bonzini
2021-07-06 21:33 ` Eduardo Habkost
2021-07-06 21:58 ` Paolo Bonzini
2021-07-07 15:08 ` Eduardo Habkost
2021-07-07 16:42 ` Jim Mattson
2021-07-07 17:08 ` Eduardo Habkost
2021-07-07 17:15 ` Jim Mattson
2021-07-07 18:23 ` Eduardo Habkost
2021-07-08 9:15 ` Paolo Bonzini
2021-07-06 21:16 ` Pawan Gupta
2021-07-06 21:19 ` Eduardo Habkost
2021-07-06 22:51 ` Pawan Gupta [this message]
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