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Message-ID: <87a58frrj7.ffs@tglx>
Date: Thu, 17 Apr 2025 12:50:04 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>, linux-kernel@...r.kernel.org
Cc: bp@...en8.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
Thomas.Lendacky@....com, nikunj@....com, Santosh.Shukla@....com,
Vasant.Hegde@....com, Suravee.Suthikulpanit@....com, David.Kaplan@....com,
x86@...nel.org, hpa@...or.com, peterz@...radead.org, seanjc@...gle.com,
pbonzini@...hat.com, kvm@...r.kernel.org, kirill.shutemov@...ux.intel.com,
huibo.wang@....com, naveen.rao@....com, francescolavra.fl@...il.com
Subject: Re: [PATCH v4 06/18] x86/apic: Add update_vector callback for
Secure AVIC
On Thu, Apr 17 2025 at 14:46, Neeraj Upadhyay wrote:
> Add update_vector callback to set/clear ALLOWED_IRR field in
> a vCPU's APIC backing page for external vectors. The ALLOWED_IRR
> field indicates the interrupt vectors which the guest allows the
> hypervisor to send (typically for emulated devices). Interrupt
> vectors used exclusively by the guest itself and the vectors which
> are not emulated by the hypervisor, such as IPI vectors, are part
> of system vectors and are not set in the ALLOWED_IRR.
Please structure changelogs properly in paragraphs:
https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#changelog
> arch/x86/include/asm/apic.h | 9 +++++
> arch/x86/kernel/apic/vector.c | 53 ++++++++++++++++++++++-------
> arch/x86/kernel/apic/x2apic_savic.c | 35 +++++++++++++++++++
And split this patch up into two:
1) Do the modifications in vector.c which is what the $Subject line
says
2) Add the SAVIC specific bits
> @@ -471,6 +473,12 @@ static __always_inline bool apic_id_valid(u32 apic_id)
> return apic_id <= apic->max_apic_id;
> }
>
> +static __always_inline void apic_update_vector(unsigned int cpu, unsigned int vector, bool set)
> +{
> + if (apic->update_vector)
> + apic->update_vector(cpu, vector, set);
> +}
This is in the public header because it can?
> -static void apic_update_vector(struct irq_data *irqd, unsigned int newvec,
> - unsigned int newcpu)
> +static int irq_alloc_vector(const struct cpumask *dest, bool resvd, unsigned int *cpu)
> +{
> + int vector;
> +
> + vector = irq_matrix_alloc(vector_matrix, dest, resvd, cpu);
int vector = irq_matrix_alloc(...);
> +
> + if (vector >= 0)
> + apic_update_vector(*cpu, vector, true);
> +
> + return vector;
> +}
> +
> +static int irq_alloc_managed_vector(unsigned int *cpu)
> +{
> + int vector;
> +
> + vector = irq_matrix_alloc_managed(vector_matrix, vector_searchmask, cpu);
> +
> + if (vector >= 0)
> + apic_update_vector(*cpu, vector, true);
> +
> + return vector;
> +}
I completely fail to see the value of these two functions. Each of them
has exactly _ONE_ call site and both sites invoke apic_update_vector()
when the allocation succeeded. Why can't you just do the obvious and
leave the existing code alone and add
if (apic->update_vector)
apic->update_vector();
into apic_update_vector()? But then you have another place where you
need the update, which does not invoke apic_update_vector().
Now if you look deeper, then you notice that all places which invoke
apic_update_vector() invoke apic_update_irq_cfg(), which is also called
at this other place, no?
> +static void irq_free_vector(unsigned int cpu, unsigned int vector, bool managed)
> +{
> + apic_update_vector(cpu, vector, false);
> + irq_matrix_free(vector_matrix, cpu, vector, managed);
> +}
This one makes sense, but please name it: apic_free_vector()
Something like the uncompiled below, no?
Thanks,
tglx
---
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -134,9 +134,19 @@ static void apic_update_irq_cfg(struct i
apicd->hw_irq_cfg.vector = vector;
apicd->hw_irq_cfg.dest_apicid = apic->calc_dest_apicid(cpu);
+
+ if (apic->update_vector)
+ apic->update_vector(cpu, vector, true);
+
irq_data_update_effective_affinity(irqd, cpumask_of(cpu));
- trace_vector_config(irqd->irq, vector, cpu,
- apicd->hw_irq_cfg.dest_apicid);
+ trace_vector_config(irqd->irq, vector, cpu, apicd->hw_irq_cfg.dest_apicid);
+}
+
+static void apic_free_vector(unsigned int cpu, unsigned int vector, bool managed)
+{
+ if (apic->update_vector)
+ apic->update_vector(cpu, vector, false);
+ irq_matrix_free(vector_matrix, cpu, vector, managed);
}
static void apic_update_vector(struct irq_data *irqd, unsigned int newvec,
@@ -174,8 +184,7 @@ static void apic_update_vector(struct ir
apicd->prev_cpu = apicd->cpu;
WARN_ON_ONCE(apicd->cpu == newcpu);
} else {
- irq_matrix_free(vector_matrix, apicd->cpu, apicd->vector,
- managed);
+ apic_free_vector(apicd->cpu, apicd->vector, managed);
}
setnew:
@@ -183,6 +192,7 @@ static void apic_update_vector(struct ir
apicd->cpu = newcpu;
BUG_ON(!IS_ERR_OR_NULL(per_cpu(vector_irq, newcpu)[newvec]));
per_cpu(vector_irq, newcpu)[newvec] = desc;
+ apic_update_irq_cfg(irqd, newvec, newcpu);
}
static void vector_assign_managed_shutdown(struct irq_data *irqd)
@@ -261,8 +271,6 @@ assign_vector_locked(struct irq_data *ir
if (vector < 0)
return vector;
apic_update_vector(irqd, vector, cpu);
- apic_update_irq_cfg(irqd, vector, cpu);
-
return 0;
}
@@ -338,7 +346,6 @@ assign_managed_vector(struct irq_data *i
if (vector < 0)
return vector;
apic_update_vector(irqd, vector, cpu);
- apic_update_irq_cfg(irqd, vector, cpu);
return 0;
}
@@ -357,7 +364,7 @@ static void clear_irq_vector(struct irq_
apicd->prev_cpu);
per_cpu(vector_irq, apicd->cpu)[vector] = VECTOR_SHUTDOWN;
- irq_matrix_free(vector_matrix, apicd->cpu, vector, managed);
+ apic_free_vector(apicd->cpu, vector, managed);
apicd->vector = 0;
/* Clean up move in progress */
@@ -366,7 +373,7 @@ static void clear_irq_vector(struct irq_
return;
per_cpu(vector_irq, apicd->prev_cpu)[vector] = VECTOR_SHUTDOWN;
- irq_matrix_free(vector_matrix, apicd->prev_cpu, vector, managed);
+ apic_free_vector(apicd->prev_cpu, vector, managed);
apicd->prev_vector = 0;
apicd->move_in_progress = 0;
hlist_del_init(&apicd->clist);
@@ -905,7 +912,7 @@ static void free_moved_vector(struct api
* affinity mask comes online.
*/
trace_vector_free_moved(apicd->irq, cpu, vector, managed);
- irq_matrix_free(vector_matrix, cpu, vector, managed);
+ apic_free_vector(cpu, vector, managed);
per_cpu(vector_irq, cpu)[vector] = VECTOR_UNUSED;
hlist_del_init(&apicd->clist);
apicd->prev_vector = 0;
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