linux-kernel - Re: [PATCH v6 15/16] x86/hyperv: implement an MSI domain for root partition

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Message-ID: <20210204175641.pzonxqrqlo7uvvze@liuwe-devbox-debian-v2>
Date:   Thu, 4 Feb 2021 17:56:41 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     Wei Liu <wei.liu@...nel.org>,
        Linux on Hyper-V List <linux-hyperv@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
        "pasha.tatashin@...een.com" <pasha.tatashin@...een.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v6 15/16] x86/hyperv: implement an MSI domain for root
 partition

On Thu, Feb 04, 2021 at 05:43:16PM +0000, Michael Kelley wrote:
[...]
> >  remove_cpuhp_state:
> > diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> > new file mode 100644
> > index 000000000000..117f17e8c88a
> > --- /dev/null
> > +++ b/arch/x86/hyperv/irqdomain.c
> > @@ -0,0 +1,362 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * for Linux to run as the root partition on Microsoft Hypervisor.
> 
> Nit:  Looks like the initial word "Irqdomain" got dropped from the above
> comment line.  But don't respin just for this.
> 

I've added it back. Thanks.

> > +static int hv_map_interrupt(union hv_device_id device_id, bool level,
> > +		int cpu, int vector, struct hv_interrupt_entry *entry)
> > +{
> > +	struct hv_input_map_device_interrupt *input;
> > +	struct hv_output_map_device_interrupt *output;
> > +	struct hv_device_interrupt_descriptor *intr_desc;
> > +	unsigned long flags;
> > +	u64 status;
> > +	cpumask_t mask = CPU_MASK_NONE;
> > +	int nr_bank, var_size;
> > +
> > +	local_irq_save(flags);
> > +
> > +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> > +
> > +	intr_desc = &input->interrupt_descriptor;
> > +	memset(input, 0, sizeof(*input));
> > +	input->partition_id = hv_current_partition_id;
> > +	input->device_id = device_id.as_uint64;
> > +	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
> > +	intr_desc->vector_count = 1;
> > +	intr_desc->target.vector = vector;
> > +
> > +	if (level)
> > +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_LEVEL;
> > +	else
> > +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;
> > +
> > +	cpumask_set_cpu(cpu, &mask);
> > +	intr_desc->target.vp_set.valid_bank_mask = 0;
> > +	intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
> > +	nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), &mask);
> 
> There's a function get_cpu_mask() that returns a pointer to a cpumask with only
> the specified cpu set in the mask.  It returns a const pointer to the correct entry
> in a pre-allocated array of all such cpumasks, so it's a lot more efficient than
> allocating and initializing a local cpumask instance on the stack.
> 

That's nice.

I've got the following diff to fix both issues. If you're happy with the
changes, can you give your Reviewed-by? That saves a round of posting.

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
index 0cabc9aece38..fa71db798465 100644
--- a/arch/x86/hyperv/irqdomain.c
+++ b/arch/x86/hyperv/irqdomain.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0

 /*
- * for Linux to run as the root partition on Microsoft Hypervisor.
+ * Irqdomain for Linux to run as the root partition on Microsoft Hypervisor.
  *
  * Authors:
  *  Sunil Muthuswamy <sunilmut@...rosoft.com>
@@ -20,7 +20,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
        struct hv_device_interrupt_descriptor *intr_desc;
        unsigned long flags;
        u64 status;
-       cpumask_t mask = CPU_MASK_NONE;
+       const cpumask_t *mask;
        int nr_bank, var_size;

        local_irq_save(flags);
@@ -41,10 +41,10 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
        else
                intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;

-       cpumask_set_cpu(cpu, &mask);
+       mask = cpumask_of(cpu);
        intr_desc->target.vp_set.valid_bank_mask = 0;
        intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
-       nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), &mask);
+       nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), mask);
        if (nr_bank < 0) {
                local_irq_restore(flags);
                pr_err("%s: unable to generate VP set\n", __func__);