Subject: [PATCH v4 22/56] KVM: arm/arm64: vgic-new: Add MMIO handling framework

From: [email-masked] (Christoffer Dall)
Date: Wed, 18 May 2016 16:29:49 +0200

On Wed, May 18, 2016 at 03:12:33PM +0100, Marc Zyngier wrote:
> On 18/05/16 13:25, Christoffer Dall wrote:
> > On Tue, May 17, 2016 at 02:33:36PM +0100, Marc Zyngier wrote:
> >> On 16/05/16 10:53, Andre Przywara wrote:
> >>> From: Marc Zyngier <[email-masked]>
> >>>
> >>> Add an MMIO handling framework to the VGIC emulation:
> >>> Each register is described by its offset, size (or number of bits per
> >>> IRQ, if applicable) and the read/write handler functions. We provide
> >>> initialization macros to describe each GIC register later easily.
> >>>
> >>> Separate dispatch functions for read and write accesses are connected
> >>> to the kvm_io_bus framework and binary-search for the responsible
> >>> register handler based on the offset address within the region.
> >>> We convert the incoming data (referenced by a pointer) to the host's
> >>> endianess and use pass-by-value to hand the data over to the actual
> >>> handler functions.
> >>>
> >>> The register handler prototype and the endianess conversion are
> >>> courtesy of Christoffer Dall.
> >>>
> >>> Signed-off-by: Marc Zyngier <[email-masked]>
> >>> Signed-off-by: Christoffer Dall <[email-masked]>
> >>> Signed-off-by: Andre Przywara <[email-masked]>
> >>> ---
> >>> Changelog RFC..v1:
> >>> - rework MMIO dispatching to use only one kvm_io_bus device
> >>> - document purpose of register region macros
> >>> - rename "this" parameter to "dev"
> >>> - change IGROUPR to be RAO (returning 1 => Group1 IRQs)
> >>>
> >>> Changelog v1 .. v2:
> >>> * MASSIVE rework:
> >>> - store register_region pointer in kvm_io_bus linked struct
> >>> - replace write_mask_xxx functions with extract_bytes() implementation
> >>> - change handler functions' prototypes to take and return unsigned long
> >>> - use binary search to find matching register handler
> >>> - convert endianess of input data in dispatch_mmio_xxx functions
> >>> - improve readability of register initializer macros
> >>> - remove any GICv2/GICv3 specific functions from vgic-mmio.c
> >>> - rename file from vgic_mmio.c to vgic-mmio.c
> >>>
> >>> Changelog v2 .. v3:
> >>> - replace inclusion of vgic/vgic.h with arm_vgic.h
> >>>
> >>> Changelog v3 .. v4:
> >>> - add IRQ number accessor macro
> >>> - check access width in dispatcher
> >>> - treat non-covered MMIO addresses as RAZ/WI
> >>> - remove extract_bytes() (re-introduced as static later in the series)
> >>>
> >>>  include/kvm/vgic/vgic.h       |  13 +++
> >>>  virt/kvm/arm/vgic/vgic-mmio.c | 184 ++++++++++++++++++++++++++++++++++++++++++
> >>>  virt/kvm/arm/vgic/vgic-mmio.h |  87 ++++++++++++++++++++
> >>>  3 files changed, 284 insertions(+)
> >>>  create mode 100644 virt/kvm/arm/vgic/vgic-mmio.c
> >>>  create mode 100644 virt/kvm/arm/vgic/vgic-mmio.h
> >>>
> >>> diff --git a/include/kvm/vgic/vgic.h b/include/kvm/vgic/vgic.h
> >>> index f663288..ff3f9c2 100644
> >>> --- a/include/kvm/vgic/vgic.h
> >>> +++ b/include/kvm/vgic/vgic.h
> >>> @@ -106,6 +106,16 @@ struct vgic_irq {
> >>>  	enum vgic_irq_config config;	/* Level or edge */
> >>>  };
> >>>  
> >>> +struct vgic_register_region;
> >>> +
> >>> +struct vgic_io_device {
> >>> +	gpa_t base_addr;
> >>> +	struct kvm_vcpu *redist_vcpu;
> >>> +	const struct vgic_register_region *regions;
> >>> +	int nr_regions;
> >>> +	struct kvm_io_device dev;
> >>> +};
> >>> +
> >>>  struct vgic_dist {
> >>>  	bool			in_kernel;
> >>>  	bool			ready;
> >>> @@ -132,6 +142,9 @@ struct vgic_dist {
> >>>  	bool			enabled;
> >>>  
> >>>  	struct vgic_irq		*spis;
> >>> +
> >>> +	struct vgic_io_device	dist_iodev;
> >>> +	struct vgic_io_device	*redist_iodevs;
> >>>  };
> >>>  
> >>>  struct vgic_v2_cpu_if {
> >>> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> >>> new file mode 100644
> >>> index 0000000..012b82b
> >>> --- /dev/null
> >>> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> >>> @@ -0,0 +1,184 @@
> >>> +/*
> >>> + * VGIC MMIO handling functions
> >>> + *
> >>> + * This program is free software; you can redistribute it and/or modify
> >>> + * it under the terms of the GNU General Public License version 2 as
> >>> + * published by the Free Software Foundation.
> >>> + *
> >>> + * This program is distributed in the hope that it will be useful,
> >>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >>> + * GNU General Public License for more details.
> >>> + */
> >>> +
> >>> +#include <linux/bitops.h>
> >>> +#include <linux/bsearch.h>
> >>> +#include <linux/kvm.h>
> >>> +#include <linux/kvm_host.h>
> >>> +#include <kvm/iodev.h>
> >>> +#include <kvm/arm_vgic.h>
> >>> +
> >>> +#include "vgic.h"
> >>> +#include "vgic-mmio.h"
> >>> +
> >>> +unsigned long vgic_mmio_read_raz(struct kvm_vcpu *vcpu,
> >>> +				 gpa_t addr, unsigned int len)
> >>> +{
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +unsigned long vgic_mmio_read_rao(struct kvm_vcpu *vcpu,
> >>> +				 gpa_t addr, unsigned int len)
> >>> +{
> >>> +	return -1UL;
> >>> +}
> >>> +
> >>> +void vgic_mmio_write_wi(struct kvm_vcpu *vcpu, gpa_t addr,
> >>> +			unsigned int len, unsigned long val)
> >>> +{
> >>> +	/* Ignore */
> >>> +}
> >>> +
> >>> +static int match_region(const void *key, const void *elt)
> >>> +{
> >>> +	const unsigned int offset = (unsigned long)key;
> >>> +	const struct vgic_register_region *region = elt;
> >>> +
> >>> +	if (offset < region->reg_offset)
> >>> +		return -1;
> >>> +
> >>> +	if (offset >= region->reg_offset + region->len)
> >>> +		return 1;
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +/* Find the proper register handler entry given a certain address offset. */
> >>> +static const struct vgic_register_region *
> >>> +vgic_find_mmio_region(const struct vgic_register_region *region, int nr_regions,
> >>> +		      unsigned int offset)
> >>> +{
> >>> +	return bsearch((void *)(uintptr_t)offset, region, nr_regions,
> >>> +		       sizeof(region[0]), match_region);
> >>> +}
> >>> +
> >>> +/*
> >>> + * kvm_mmio_read_buf() returns a value in a format where it can be converted
> >>> + * to a byte array and be directly observed as the guest wanted it to appear
> >>> + * in memory if it had done the store itself, which is LE for the GIC, as the
> >>> + * guest knows the GIC is always LE.
> >>> + *
> >>> + * We convert this value to the CPUs native format to deal with it as a data
> >>> + * value.
> >>> + */
> >>> +unsigned long vgic_data_mmio_bus_to_host(const void *val, unsigned int len)
> >>> +{
> >>> +	unsigned long data = kvm_mmio_read_buf(val, len);
> >>> +
> >>> +	switch (len) {
> >>> +	case 1:
> >>> +		return data;
> >>> +	case 2:
> >>> +		return le16_to_cpu(data);
> >>> +	case 4:
> >>> +		return le32_to_cpu(data);
> >>> +	default:
> >>> +		return le64_to_cpu(data);
> >>> +	}
> >>> +}
> >>> +
> >>> +/*
> >>> + * kvm_mmio_write_buf() expects a value in a format such that if converted to
> >>> + * a byte array it is observed as the guest would see it if it could perform
> >>> + * the load directly.  Since the GIC is LE, and the guest knows this, the
> >>> + * guest expects a value in little endian format.
> >>> + *
> >>> + * We convert the data value from the CPUs native format to LE so that the
> >>> + * value is returned in the proper format.
> >>> + */
> >>> +void vgic_data_host_to_mmio_bus(void *buf, unsigned int len,
> >>> +				unsigned long data)
> >>> +{
> >>> +	switch (len) {
> >>> +	case 1:
> >>> +		break;
> >>> +	case 2:
> >>> +		data = cpu_to_le16(data);
> >>> +		break;
> >>> +	case 4:
> >>> +		data = cpu_to_le32(data);
> >>> +		break;
> >>> +	default:
> >>> +		data = cpu_to_le64(data);
> >>> +	}
> >>> +
> >>> +	kvm_mmio_write_buf(buf, len, data);
> >>> +}
> >>> +
> >>> +static
> >>> +struct vgic_io_device *kvm_to_vgic_iodev(const struct kvm_io_device *dev)
> >>> +{
> >>> +	return container_of(dev, struct vgic_io_device, dev);
> >>> +}
> >>> +
> >>> +static bool check_region(const struct vgic_register_region *region,
> >>> +			 gpa_t addr, int len)
> >>> +{
> >>> +	if ((region->access_flags & VGIC_ACCESS_8bit) && len == 1)
> >>> +		return true;
> >>> +	if ((region->access_flags & VGIC_ACCESS_32bit) &&
> >>> +	    len == sizeof(u32) && !(addr & 3))
> >>> +		return true;
> >>> +	if ((region->access_flags & VGIC_ACCESS_64bit) &&
> >>> +	    len == sizeof(u64) && !(addr & 7))
> >>> +		return true;
> >>> +
> >>> +	return false;
> >>> +}
> >>> +
> >>> +static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> >>> +			      gpa_t addr, int len, void *val)
> >>> +{
> >>> +	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
> >>> +	const struct vgic_register_region *region;
> >>> +	struct kvm_vcpu *r_vcpu;
> >>> +	unsigned long data;
> >>> +
> >>> +	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
> >>> +				       addr - iodev->base_addr);
> >>> +	if (!region || !check_region(region, addr, len)) {
> >>> +		memset(val, 0, len);
> >>> +		return 0;
> >>> +	}
> >>> +
> >>> +	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
> >>> +	data = region->read(r_vcpu, addr, len);
> >>> +	vgic_data_host_to_mmio_bus(val, len, data);
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int dispatch_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> >>> +			       gpa_t addr, int len, const void *val)
> >>> +{
> >>> +	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
> >>> +	const struct vgic_register_region *region;
> >>> +	struct kvm_vcpu *r_vcpu;
> >>> +	unsigned long data = vgic_data_mmio_bus_to_host(val, len);
> >>> +
> >>> +	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
> >>> +				       addr - iodev->base_addr);
> >>> +	if (!region)
> >>> +		return 0;
> >>> +
> >>> +	if (!check_region(region, addr, len))
> >>> +		return 0;
> >>> +
> >>> +	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
> >>> +	region->write(r_vcpu, addr, len, data);
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +struct kvm_io_device_ops kvm_io_gic_ops = {
> >>> +	.read = dispatch_mmio_read,
> >>> +	.write = dispatch_mmio_write,
> >>> +};
> >>> diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
> >>> new file mode 100644
> >>> index 0000000..855b1db
> >>> --- /dev/null
> >>> +++ b/virt/kvm/arm/vgic/vgic-mmio.h
> >>> @@ -0,0 +1,87 @@
> >>> +/*
> >>> + * Copyright (C) 2015, 2016 ARM Ltd.
> >>> + *
> >>> + * This program is free software; you can redistribute it and/or modify
> >>> + * it under the terms of the GNU General Public License version 2 as
> >>> + * published by the Free Software Foundation.
> >>> + *
> >>> + * This program is distributed in the hope that it will be useful,
> >>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >>> + * GNU General Public License for more details.
> >>> + *
> >>> + * You should have received a copy of the GNU General Public License
> >>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> >>> + */
> >>> +#ifndef __KVM_ARM_VGIC_MMIO_H__
> >>> +#define __KVM_ARM_VGIC_MMIO_H__
> >>> +
> >>> +struct vgic_register_region {
> >>> +	unsigned int reg_offset;
> >>> +	unsigned int len;
> >>> +	unsigned int bits_per_irq;
> >>> +	unsigned int access_flags;
> >>> +	unsigned long (*read)(struct kvm_vcpu *vcpu, gpa_t addr,
> >>> +			      unsigned int len);
> >>> +	void (*write)(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len,
> >>> +		      unsigned long val);
> >>> +};
> >>> +
> >>> +extern struct kvm_io_device_ops kvm_io_gic_ops;
> >>> +
> >>> +#define VGIC_ACCESS_8bit	1
> >>> +#define VGIC_ACCESS_32bit	2
> >>> +#define VGIC_ACCESS_64bit	4
> >>> +
> >>> +/* generate a mask that covers 1024 interrupts with <b> bits per IRQ */
> >>
> >> Hmmm. I'd appreciate some additional comments, specially when it comes
> >> to the various restrictions. May I'd suggest something like:
> >>
> >> /*
> >>  * Generate a mask that covers the number of bytes required to address
> >>  * up to 1024 interrupts, each represented by <b> bits. This assumes
> >>  * that <b> is a power of two.
> >>  *
> >>  * ilog2(b) + ilog2(1024) is the number of bits required to bit-address
> >>  * 1024 interrupts, each represented by b bits. Minus ilog2(8) converts
> >>  * this to a byte address.
> > 
> > So I'm guessting this is a rewrite of ilog2( (b * 1024) / 8), but I'm
> 
> Yes, same thing.
> 
> > stupid enough to not understand our use of logarithms here.  Can someone
> > remind me whatever I forgot at CS 101?
> 
> I'm bad at explaining that kind of things, so let me just quote
> Wikipedia (https://en.wikipedia.org/wiki/Binary_logarithm):
> 
> "The number of digits (bits) in the binary representation of a positive
> integer n is the integral part of 1 + log2?n"
> 
> Is that what you were missing?
> 

yeah, duh, I feel stupid now.  Mind if we add this "note to
Christoffer's brain" to the comment:

"Since n bits can address a maximum of N=n^2 values, we get the number of
bits required to address a number of values by applying log2(N).  With
N being 1024 * b, we get  that ilog(b) + ilog2(1024) is the number..."

> > 
> >>  */
> >>
> >>> +#define VGIC_ADDR_IRQ_MASK(b) GENMASK_ULL(ilog2(b) + ilog2(1024) - \
> >>> +					  ilog2(BITS_PER_BYTE) - 1, 0)
> >>
> >> /*
> >>  * Convert a base address into a base interrupt (each interrupt
> >>  * represented by <bits> bits. This assumes that <bits> is a power
> >>  * of two, that <addr> both part of a memory region aligned on a
> > 
> > did you mean '<addr> *is* both part of' ?
> 
> Indeed.
> 

Thanks,
-Christoffer