From: Auger Eric <eric.auger@redhat.com> To: Peter Maydell <peter.maydell@linaro.org> Cc: Marc Zyngier <marc.zyngier@arm.com>, lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>, arm-mail-list <linux-arm-kernel@lists.infradead.org>, kvmarm@lists.cs.columbia.edu Subject: Re: [REPOST PATCH] arm/arm64: KVM: Add PSCI version selection API Date: Mon, 5 Mar 2018 21:37:08 +0100 [thread overview] Message-ID: <a1579f14-a5fe-11bc-a831-f729cead25ba@redhat.com> (raw) In-Reply-To: <CAFEAcA9=YpNngKqeOXiO7QDvL=1ZaQEW8fh3XHjwD+i8qQm9wg@mail.gmail.com> Hi Peter, On 05/03/18 17:31, Peter Maydell wrote: > On 2 March 2018 at 12:26, Auger Eric <eric.auger@redhat.com> wrote: >> Hi Marc, >> On 02/03/18 12:11, Marc Zyngier wrote: >>> On Fri, 02 Mar 2018 10:44:48 +0000, >>> Auger Eric wrote: >>>> I understand the get/set is called as part of the migration process. >>>> So my understanding is the benefit of this series is migration fails in >>>> those cases: >>>> >>>>> =0.2 source -> 0.1 destination >>>> 0.1 source -> >=0.2 destination >>> >>> It also fails in the case where you migrate a 1.0 guest to something >>> that cannot support it. >> >> That's because on the destination, the number of regs is less than on >> source, right? > > I think it fails because the KVM_REG_ARM_PSCI_VERSION register will be > in the migration state but not in the destination's list of registers: > the code in QEMU's target/arm/machine.c:cpu_post_load() function that > checks "register in their list but not ours: fail migration" will > catch this. Thank you for the pointer. Yes at the time I reviewed the patch and just focusing on the kernel code, this was not immediate to me. > > That also means that we will fail migration from a new kernel where > we've specifically asked for PSCI 0.2 to an old PSCI-0.2-only kernel > (because the KVM_REG_ARM_PSCI_VERSION reg will appear in the migration > stream even if its value is the one value that matches the old kernel > behaviour). I don't know if we care about that. Do you know when are we likely to force PSCI 0.2 on a new kernel? At which layer is the decision supposed to be made and on which criteria? Thanks Eric > > thanks > -- PMM >
WARNING: multiple messages have this Message-ID (diff)
From: eric.auger@redhat.com (Auger Eric) To: linux-arm-kernel@lists.infradead.org Subject: [REPOST PATCH] arm/arm64: KVM: Add PSCI version selection API Date: Mon, 5 Mar 2018 21:37:08 +0100 [thread overview] Message-ID: <a1579f14-a5fe-11bc-a831-f729cead25ba@redhat.com> (raw) In-Reply-To: <CAFEAcA9=YpNngKqeOXiO7QDvL=1ZaQEW8fh3XHjwD+i8qQm9wg@mail.gmail.com> Hi Peter, On 05/03/18 17:31, Peter Maydell wrote: > On 2 March 2018 at 12:26, Auger Eric <eric.auger@redhat.com> wrote: >> Hi Marc, >> On 02/03/18 12:11, Marc Zyngier wrote: >>> On Fri, 02 Mar 2018 10:44:48 +0000, >>> Auger Eric wrote: >>>> I understand the get/set is called as part of the migration process. >>>> So my understanding is the benefit of this series is migration fails in >>>> those cases: >>>> >>>>> =0.2 source -> 0.1 destination >>>> 0.1 source -> >=0.2 destination >>> >>> It also fails in the case where you migrate a 1.0 guest to something >>> that cannot support it. >> >> That's because on the destination, the number of regs is less than on >> source, right? > > I think it fails because the KVM_REG_ARM_PSCI_VERSION register will be > in the migration state but not in the destination's list of registers: > the code in QEMU's target/arm/machine.c:cpu_post_load() function that > checks "register in their list but not ours: fail migration" will > catch this. Thank you for the pointer. Yes at the time I reviewed the patch and just focusing on the kernel code, this was not immediate to me. > > That also means that we will fail migration from a new kernel where > we've specifically asked for PSCI 0.2 to an old PSCI-0.2-only kernel > (because the KVM_REG_ARM_PSCI_VERSION reg will appear in the migration > stream even if its value is the one value that matches the old kernel > behaviour). I don't know if we care about that. Do you know when are we likely to force PSCI 0.2 on a new kernel? At which layer is the decision supposed to be made and on which criteria? Thanks Eric > > thanks > -- PMM >
next prev parent reply other threads:[~2018-03-05 20:37 UTC|newest] Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-02-15 17:58 [REPOST PATCH] arm/arm64: KVM: Add PSCI version selection API Marc Zyngier 2018-02-15 17:58 ` Marc Zyngier 2018-03-02 10:44 ` Auger Eric 2018-03-02 10:44 ` Auger Eric 2018-03-02 11:11 ` Marc Zyngier 2018-03-02 11:11 ` Marc Zyngier 2018-03-02 11:11 ` Marc Zyngier 2018-03-02 12:26 ` Auger Eric 2018-03-02 12:26 ` Auger Eric 2018-03-05 16:31 ` Peter Maydell 2018-03-05 16:31 ` Peter Maydell 2018-03-05 20:37 ` Auger Eric [this message] 2018-03-05 20:37 ` Auger Eric 2018-03-06 9:50 ` Marc Zyngier 2018-03-06 9:50 ` Marc Zyngier 2018-03-06 10:12 ` Peter Maydell 2018-03-06 10:12 ` Peter Maydell 2018-03-06 10:52 ` Marc Zyngier 2018-03-06 10:52 ` Marc Zyngier 2018-03-05 16:47 ` Peter Maydell 2018-03-05 16:47 ` Peter Maydell 2018-03-06 9:21 ` Andrew Jones 2018-03-06 9:21 ` Andrew Jones 2018-03-15 19:00 ` Marc Zyngier 2018-03-15 19:00 ` Marc Zyngier 2018-03-15 19:13 ` Peter Maydell 2018-03-15 19:13 ` Peter Maydell 2018-03-15 19:26 ` Marc Zyngier 2018-03-15 19:26 ` Marc Zyngier 2018-04-09 12:30 ` Christoffer Dall 2018-04-09 12:30 ` Christoffer Dall 2018-04-09 12:47 ` Marc Zyngier 2018-04-09 12:47 ` Marc Zyngier 2018-04-09 13:05 ` Christoffer Dall 2018-04-09 13:05 ` Christoffer Dall 2018-04-09 13:20 ` Marc Zyngier 2018-04-09 13:20 ` Marc Zyngier
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