From: James Morse <james.morse@arm.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, x86@kernel.org,
Marc Zyngier <maz@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Huacai Chen <chenhuacai@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Len Brown <lenb@kernel.org>, Rafael Wysocki <rafael@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Salil Mehta <salil.mehta@huawei.com>,
Russell King <linux@armlinux.org.uk>,
Jean-Philippe Brucker <jean-philippe@linaro.org>
Subject: Re: [RFC PATCH 29/32] KVM: arm64: Pass hypercalls to userspace
Date: Tue, 7 Feb 2023 17:50:59 +0000 [thread overview]
Message-ID: <0621bf8e-06f2-70f2-6d2b-f311c5a4ffce@arm.com> (raw)
In-Reply-To: <Y913sIqWxmf4O5oG@google.com>
Hi Oliver,
On 03/02/2023 21:08, Oliver Upton wrote:
> On Fri, Feb 03, 2023 at 01:50:40PM +0000, James Morse wrote:
>> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>
>> When capability KVM_CAP_ARM_HVC_TO_USER is available, userspace can
>> request to handle all hypercalls that aren't handled by KVM.
> I would very much prefer we not go down this route. This capability
> effectively constructs an ABI out of what KVM presently does not
> implement. What would happen if KVM decides to implement a new set
> of hypercalls later down the road that were previously forwarded to
> userspace?
The user-space support would never get called. If we have a wild-west allocation of IDs in
this area we have bigger problems. I'd hope in this example it would be a VMM or an
in-kernel implementation of the same feature.
When I floated something like this before for supporting SDEI in guests, Christoffer
didn't like tie-ing KVM to SMC-CC - hence the all or nothing.
Since then we've had things like Spectre, which I don't think the VMM should
ever be allowed to handle, which makes the whole thing much murkier.
> Instead of a catch-all I think we should take the approach of having
> userspace explicitly request which hypercalls should be forwarded to
> userspace. I proposed something similar [1], but never got around to
> respinning it (oops).
> Let me dust those patches off and align with Marc's suggestions.
>
> [1]: https://lore.kernel.org/kvmarm/20221110015327.3389351-1-oliver.upton@linux.dev/
I've no problem with doing it like this. This approach was based on Christoffer's previous
feedback, but the world has changed since then.
Let me know if you want me to re-spin that series - I need to get this into some
shape next week for Salil to look at the Qemu changes, as I can't test the whole thing
until that is done.
Thanks,
James
WARNING: multiple messages have this Message-ID (diff)
From: James Morse <james.morse@arm.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, x86@kernel.org,
Marc Zyngier <maz@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Huacai Chen <chenhuacai@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Len Brown <lenb@kernel.org>, Rafael Wysocki <rafael@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Salil Mehta <salil.mehta@huawei.com>,
Russell King <linux@armlinux.org.uk>,
Jean-Philippe Brucker <jean-philippe@linaro.org>
Subject: Re: [RFC PATCH 29/32] KVM: arm64: Pass hypercalls to userspace
Date: Tue, 7 Feb 2023 17:50:59 +0000 [thread overview]
Message-ID: <0621bf8e-06f2-70f2-6d2b-f311c5a4ffce@arm.com> (raw)
In-Reply-To: <Y913sIqWxmf4O5oG@google.com>
Hi Oliver,
On 03/02/2023 21:08, Oliver Upton wrote:
> On Fri, Feb 03, 2023 at 01:50:40PM +0000, James Morse wrote:
>> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>
>> When capability KVM_CAP_ARM_HVC_TO_USER is available, userspace can
>> request to handle all hypercalls that aren't handled by KVM.
> I would very much prefer we not go down this route. This capability
> effectively constructs an ABI out of what KVM presently does not
> implement. What would happen if KVM decides to implement a new set
> of hypercalls later down the road that were previously forwarded to
> userspace?
The user-space support would never get called. If we have a wild-west allocation of IDs in
this area we have bigger problems. I'd hope in this example it would be a VMM or an
in-kernel implementation of the same feature.
When I floated something like this before for supporting SDEI in guests, Christoffer
didn't like tie-ing KVM to SMC-CC - hence the all or nothing.
Since then we've had things like Spectre, which I don't think the VMM should
ever be allowed to handle, which makes the whole thing much murkier.
> Instead of a catch-all I think we should take the approach of having
> userspace explicitly request which hypercalls should be forwarded to
> userspace. I proposed something similar [1], but never got around to
> respinning it (oops).
> Let me dust those patches off and align with Marc's suggestions.
>
> [1]: https://lore.kernel.org/kvmarm/20221110015327.3389351-1-oliver.upton@linux.dev/
I've no problem with doing it like this. This approach was based on Christoffer's previous
feedback, but the world has changed since then.
Let me know if you want me to re-spin that series - I need to get this into some
shape next week for Salil to look at the Qemu changes, as I can't test the whole thing
until that is done.
Thanks,
James
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: James Morse <james.morse@arm.com>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: linux-pm@vger.kernel.org, loongarch@lists.linux.dev,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, x86@kernel.org,
Marc Zyngier <maz@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Huacai Chen <chenhuacai@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Len Brown <lenb@kernel.org>, Rafael Wysocki <rafael@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Salil Mehta <salil.mehta@huawei.com>,
Russell King <linux@armlinux.org.uk>,
Jean-Philippe Brucker <jean-philippe@linaro.org>
Subject: Re: [RFC PATCH 29/32] KVM: arm64: Pass hypercalls to userspace
Date: Tue, 07 Feb 2023 17:50:59 +0000 [thread overview]
Message-ID: <0621bf8e-06f2-70f2-6d2b-f311c5a4ffce@arm.com> (raw)
In-Reply-To: <Y913sIqWxmf4O5oG@google.com>
Hi Oliver,
On 03/02/2023 21:08, Oliver Upton wrote:
> On Fri, Feb 03, 2023 at 01:50:40PM +0000, James Morse wrote:
>> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>
>> When capability KVM_CAP_ARM_HVC_TO_USER is available, userspace can
>> request to handle all hypercalls that aren't handled by KVM.
> I would very much prefer we not go down this route. This capability
> effectively constructs an ABI out of what KVM presently does not
> implement. What would happen if KVM decides to implement a new set
> of hypercalls later down the road that were previously forwarded to
> userspace?
The user-space support would never get called. If we have a wild-west allocation of IDs in
this area we have bigger problems. I'd hope in this example it would be a VMM or an
in-kernel implementation of the same feature.
When I floated something like this before for supporting SDEI in guests, Christoffer
didn't like tie-ing KVM to SMC-CC - hence the all or nothing.
Since then we've had things like Spectre, which I don't think the VMM should
ever be allowed to handle, which makes the whole thing much murkier.
> Instead of a catch-all I think we should take the approach of having
> userspace explicitly request which hypercalls should be forwarded to
> userspace. I proposed something similar [1], but never got around to
> respinning it (oops).
> Let me dust those patches off and align with Marc's suggestions.
>
> [1]: https://lore.kernel.org/kvmarm/20221110015327.3389351-1-oliver.upton@linux.dev/
I've no problem with doing it like this. This approach was based on Christoffer's previous
feedback, but the world has changed since then.
Let me know if you want me to re-spin that series - I need to get this into some
shape next week for Salil to look at the Qemu changes, as I can't test the whole thing
until that is done.
Thanks,
James
next prev parent reply other threads:[~2023-02-07 17:51 UTC|newest]
Thread overview: 164+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-03 13:50 [RFC PATCH 00/32] ACPI/arm64: add support for virtual cpuhotplug James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 01/32] ia64: Fix build error due to switch case label appearing next to declaration James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 02/32] ACPI: Move ACPI_HOTPLUG_CPU to be enabled per architecture James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-08-30 18:31 ` Russell King (Oracle)
2023-08-30 18:31 ` Russell King (Oracle)
2023-02-03 13:50 ` [RFC PATCH 03/32] drivers: base: Use present CPUs in GENERIC_CPU_DEVICES James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 04/32] drivers: base: Allow parts of GENERIC_CPU_DEVICES to be overridden James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 05/32] drivers: base: Move cpu_dev_init() after node_dev_init() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 06/32] arm64: setup: Switch over to GENERIC_CPU_DEVICES using arch_register_cpu() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 07/32] ia64/topology: Switch over to GENERIC_CPU_DEVICES James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 08/32] x86/topology: " James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 09/32] LoongArch: " James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 10/32] arch_topology: Make register_cpu_capacity_sysctl() tolerant to late CPUs James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 11/32] ACPI: processor: Add support for processors described as container packages James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 12/32] ACPI: processor: Register CPUs that are online, but not described in the DSDT James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 13/32] ACPI: processor: Register all CPUs from acpi_processor_get_info() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 14/32] ACPI: Rename ACPI_HOTPLUG_CPU to include 'present' James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 15/32] ACPI: Move acpi_bus_trim_one() before acpi_scan_hot_remove() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 16/32] ACPI: Rename acpi_processor_hotadd_init and remove pre-processor guards James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 17/32] ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 18/32] ACPI: Check _STA present bit before making CPUs not present James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 19/32] ACPI: Warn when the present bit changes but the feature is not enabled James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 20/32] drivers: base: Implement weak arch_unregister_cpu() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 21/32] LoongArch: Use the __weak version of arch_unregister_cpu() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 22/32] arm64: acpi: Move get_cpu_for_acpi_id() to a header James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 23/32] ACPICA: Add new MADT GICC flags fields [code first?] James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 24/32] arm64, irqchip/gic-v3, ACPI: Move MADT GICC enabled check into a helper James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 25/32] irqchip/gic-v3: Don't return errors from gic_acpi_match_gicc() James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 26/32] irqchip/gic-v3: Add support for ACPI's disabled but 'online capable' CPUs James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 27/32] arm64: psci: Ignore DENIED CPUs James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 28/32] ACPI: add support to register CPUs based on the _STA enabled bit James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 29/32] KVM: arm64: Pass hypercalls to userspace James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 21:08 ` Oliver Upton
2023-02-03 21:08 ` Oliver Upton
2023-02-03 21:08 ` Oliver Upton
2023-02-07 17:50 ` James Morse [this message]
2023-02-07 17:50 ` James Morse
2023-02-07 17:50 ` James Morse
2023-02-08 9:02 ` Marc Zyngier
2023-02-08 9:02 ` Marc Zyngier
2023-02-05 10:12 ` Marc Zyngier
2023-02-05 10:12 ` Marc Zyngier
2023-02-06 10:10 ` Suzuki K Poulose
2023-02-06 10:10 ` Suzuki K Poulose
2023-02-06 10:10 ` Suzuki K Poulose
2023-02-06 12:31 ` Marc Zyngier
2023-02-06 12:31 ` Marc Zyngier
2023-02-07 9:41 ` Suzuki K Poulose
2023-02-07 9:41 ` Suzuki K Poulose
2023-02-07 9:41 ` Suzuki K Poulose
2023-02-07 11:23 ` Marc Zyngier
2023-02-07 11:23 ` Marc Zyngier
2023-02-07 12:46 ` Suzuki K Poulose
2023-02-07 12:46 ` Suzuki K Poulose
2023-02-07 12:46 ` Suzuki K Poulose
2023-02-06 17:19 ` Oliver Upton
2023-02-06 17:19 ` Oliver Upton
2023-02-06 17:19 ` Oliver Upton
2023-02-07 17:50 ` James Morse
2023-02-07 17:50 ` James Morse
2023-02-07 17:50 ` James Morse
2023-02-08 8:40 ` Marc Zyngier
2023-02-08 8:40 ` Marc Zyngier
2023-02-08 14:25 ` Marc Zyngier
2023-02-08 14:25 ` Marc Zyngier
2023-02-11 1:44 ` Oliver Upton
2023-02-11 1:44 ` Oliver Upton
2023-02-03 13:50 ` [RFC PATCH 30/32] KVM: arm64: Pass PSCI calls " James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-05-23 9:32 ` Salil Mehta
2023-05-23 9:32 ` Salil Mehta
2023-05-23 9:32 ` Salil Mehta
2023-09-12 17:01 ` James Morse
2023-09-12 17:01 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 31/32] arm64: document virtual CPU hotplug's expectations James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` [RFC PATCH 32/32] cpumask: Add enabled cpumask for present CPUs that can be brought online James Morse
2023-02-03 13:50 ` James Morse
2023-02-03 13:50 ` James Morse
2023-03-07 12:00 ` [RFC PATCH 00/32] ACPI/arm64: add support for virtual cpuhotplug Jonathan Cameron
2023-03-07 12:00 ` Jonathan Cameron
2023-03-07 12:00 ` Jonathan Cameron
2023-03-13 15:50 ` James Morse
2023-03-13 15:50 ` James Morse
2023-03-14 11:02 ` Jonathan Cameron
2023-03-14 11:02 ` Jonathan Cameron
2023-03-14 11:02 ` Jonathan Cameron
2023-03-29 2:35 ` Gavin Shan
2023-03-29 2:35 ` Gavin Shan
2023-03-29 2:35 ` Gavin Shan
2023-09-12 17:01 ` James Morse
2023-09-12 17:01 ` James Morse
2023-09-12 22:38 ` Gavin Shan
2023-09-12 22:38 ` Gavin Shan
2023-09-13 15:28 ` Russell King (Oracle)
2023-09-13 15:28 ` Russell King (Oracle)
2023-03-29 5:52 ` Shaoqin Huang
2023-03-29 5:52 ` Shaoqin Huang
2023-03-29 5:52 ` Shaoqin Huang
2023-04-03 6:25 ` Gavin Shan
2023-04-03 6:25 ` Gavin Shan
2023-04-03 6:25 ` Gavin Shan
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