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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>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Maciej W. Rozycki" <macro@orcam.me.uk>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Vlastimil Babka <vbabka@suse.cz>, Tony Luck <tony.luck@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Kyung Min Park <kyung.min.park@intel.com>,
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	Anand K Mistry <amistry@google.com>,
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	linux-perf-users@vger.kernel.org, kvm@vger.kernel.org
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

      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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