From: Alexandru Elisei <alexandru.elisei@arm.com> To: Marc Zyngier <maz@kernel.org> Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] KVM/arm64: Don't emulate a PMU for 32-bit guests if feature not set Date: Tue, 26 Apr 2022 10:30:18 +0100 [thread overview] Message-ID: <Yme7h7xngl4l22bE@monolith.localdoman> (raw) In-Reply-To: <875ymx9jbu.wl-maz@kernel.org> Hi, On Mon, Apr 25, 2022 at 06:14:13PM +0100, Marc Zyngier wrote: > [+ Oliver] > > Hi Alex, > > On Mon, 25 Apr 2022 15:55:30 +0100, > Alexandru Elisei <alexandru.elisei@arm.com> wrote: > > > > kvm->arch.arm_pmu is set when userspace attempts to set the first PMU > > attribute. As certain attributes are mandatory, arm_pmu ends up always > > being set to a valid arm_pmu, otherwise KVM will refuse to run the VCPU. > > However, this only happens if the VCPU has the PMU feature. If the VCPU > > doesn't have the feature bit set, kvm->arch.arm_pmu will be left > > uninitialized and equal to NULL. > > Although I'm not opposed to this as an immediate workaround to avoid > the ugly crash, I think sanitising the AArch32 regs is the way to go. I agree. This patch is just a band-aid. > Oliver had a stab at this a few weeks back[1], but this seem to have > stalled. > > Could you have a look and see if anything was missing (the patches > needed some rework, but I haven't checked whether DFR0 was correctly > handled or not). I'll have a look. Thanks, Alex > > Thanks, > > M. > > [1] https://lore.kernel.org/r/20220401010832.3425787-1-oupton@google.com > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Alexandru Elisei <alexandru.elisei@arm.com> To: Marc Zyngier <maz@kernel.org> Cc: james.morse@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, Oliver Upton <oupton@google.com> Subject: Re: [PATCH] KVM/arm64: Don't emulate a PMU for 32-bit guests if feature not set Date: Tue, 26 Apr 2022 10:30:18 +0100 [thread overview] Message-ID: <Yme7h7xngl4l22bE@monolith.localdoman> (raw) In-Reply-To: <875ymx9jbu.wl-maz@kernel.org> Hi, On Mon, Apr 25, 2022 at 06:14:13PM +0100, Marc Zyngier wrote: > [+ Oliver] > > Hi Alex, > > On Mon, 25 Apr 2022 15:55:30 +0100, > Alexandru Elisei <alexandru.elisei@arm.com> wrote: > > > > kvm->arch.arm_pmu is set when userspace attempts to set the first PMU > > attribute. As certain attributes are mandatory, arm_pmu ends up always > > being set to a valid arm_pmu, otherwise KVM will refuse to run the VCPU. > > However, this only happens if the VCPU has the PMU feature. If the VCPU > > doesn't have the feature bit set, kvm->arch.arm_pmu will be left > > uninitialized and equal to NULL. > > Although I'm not opposed to this as an immediate workaround to avoid > the ugly crash, I think sanitising the AArch32 regs is the way to go. I agree. This patch is just a band-aid. > Oliver had a stab at this a few weeks back[1], but this seem to have > stalled. > > Could you have a look and see if anything was missing (the patches > needed some rework, but I haven't checked whether DFR0 was correctly > handled or not). I'll have a look. Thanks, Alex > > Thanks, > > M. > > [1] https://lore.kernel.org/r/20220401010832.3425787-1-oupton@google.com > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-04-26 9:30 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-25 14:55 [PATCH] KVM/arm64: Don't emulate a PMU for 32-bit guests if feature not set Alexandru Elisei 2022-04-25 14:55 ` Alexandru Elisei 2022-04-25 17:14 ` Marc Zyngier 2022-04-25 17:14 ` Marc Zyngier 2022-04-25 17:26 ` Oliver Upton 2022-04-25 17:26 ` Oliver Upton 2022-04-26 9:30 ` Alexandru Elisei [this message] 2022-04-26 9:30 ` Alexandru Elisei 2022-04-26 8:05 ` Oliver Upton 2022-04-26 8:05 ` Oliver Upton 2022-04-26 9:01 ` Alexandru Elisei 2022-04-26 9:01 ` Alexandru Elisei 2022-04-27 7:57 ` Oliver Upton 2022-04-27 7:57 ` Oliver Upton 2022-04-27 9:45 ` Alexandru Elisei 2022-04-27 9:45 ` Alexandru Elisei 2022-04-27 21:10 ` Marc Zyngier 2022-04-27 21:10 ` Marc Zyngier 2022-04-28 19:58 ` Marc Zyngier 2022-04-28 19:58 ` Marc Zyngier
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