linux-kernel - Re: [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest

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Message-ID: <42698e3c-c382-8621-7d9e-af09398f4aef@huawei.com>
Date:   Tue, 13 Aug 2019 14:06:56 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Steven Price <steven.price@....com>
CC:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        <linux-doc@...r.kernel.org>, Russell King <linux@...linux.org.uk>,
        <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Will Deacon <will@...nel.org>, <kvmarm@...ts.cs.columbia.edu>
Subject: Re: [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest

On 2019/8/12 18:39, Steven Price wrote:
> On 09/08/2019 14:51, Zenghui Yu wrote:
> [...]
>> Hi Steven,
>>
>> Since userspace is not involved yet (right?), no one will create the
>> PV_TIME device for guest (and no one will specify the IPA of the shared
>> stolen time region), and I guess we will get a "not supported" error
>> here.
>>
>> So what should we do if we want to test this series now?  Any userspace
>> tools?  If no, do you have any plans for userspace developing? ;-)
> 
> At the moment I have the following patch to kvmtool which creates the
> PV_TIME device - this isn't in a state to go upstream, and Marc has
> asked that I rework the memory allocation, so this will need to change.
> 
> It's a little ugly as it simply reserves the first page of RAM to use
> for the PV time structures.

Thanks for sharing the code. It's good enough to show what is required
in user-space.

(I'm not familiar with kvmtool. I will first take some time to move the
steal time part to Qemu and see what will happen.)


Thanks,
zenghui

> ----8<----
> diff --git a/Makefile b/Makefile
> index 3862112..a79956b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -158,7 +158,7 @@ endif
>   # ARM
>   OBJS_ARM_COMMON		:= arm/fdt.o arm/gic.o arm/gicv2m.o arm/ioport.o \
>   			   arm/kvm.o arm/kvm-cpu.o arm/pci.o arm/timer.o \
> -			   arm/pmu.o
> +			   arm/pmu.o arm/pvtime.o
>   HDRS_ARM_COMMON		:= arm/include
>   ifeq ($(ARCH), arm)
>   	DEFINES		+= -DCONFIG_ARM
> diff --git a/arm/fdt.c b/arm/fdt.c
> index c80e6da..19eccbc 100644
> --- a/arm/fdt.c
> +++ b/arm/fdt.c
> @@ -119,6 +119,7 @@ static int setup_fdt(struct kvm *kvm)
>   
>   	/* Create new tree without a reserve map */
>   	_FDT(fdt_create(fdt, FDT_MAX_SIZE));
> +	_FDT(fdt_add_reservemap_entry(fdt, kvm->arch.memory_guest_start, 4096));
>   	_FDT(fdt_finish_reservemap(fdt));
>   
>   	/* Header */
> diff --git a/arm/kvm.c b/arm/kvm.c
> index 1f85fc6..8bbfef1 100644
> --- a/arm/kvm.c
> +++ b/arm/kvm.c
> @@ -11,6 +11,8 @@
>   #include <linux/kvm.h>
>   #include <linux/sizes.h>
>   
> +int pvtime_create(struct kvm *kvm);
> +
>   struct kvm_ext kvm_req_ext[] = {
>   	{ DEFINE_KVM_EXT(KVM_CAP_IRQCHIP) },
>   	{ DEFINE_KVM_EXT(KVM_CAP_ONE_REG) },
> @@ -86,6 +88,10 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size)
>   	/* Create the virtual GIC. */
>   	if (gic__create(kvm, kvm->cfg.arch.irqchip))
>   		die("Failed to create virtual GIC");
> +
> +	/* Setup PV time */
> +	if (pvtime_create(kvm))
> +		die("Failed to initialise PV time");
>   }
>   
>   #define FDT_ALIGN	SZ_2M
> diff --git a/arm/pvtime.c b/arm/pvtime.c
> new file mode 100644
> index 0000000..abcaab3
> --- /dev/null
> +++ b/arm/pvtime.c
> @@ -0,0 +1,77 @@
> +#include "kvm/kvm.h"
> +
> +#define KVM_DEV_TYPE_ARM_PV_TIME (KVM_DEV_TYPE_ARM_VGIC_ITS+2)
> +
> +/* Device Control API: PV_TIME */
> +#define KVM_DEV_ARM_PV_TIME_PADDR	0
> +#define KVM_DEV_ARM_PV_TIME_FREQUENCY	3
> +
> +#define KVM_DEV_ARM_PV_TIME_ST		0
> +#define KVM_DEV_ARM_PV_TIME_LPT		1
> +
> +static int pvtime_fd;
> +
> +int pvtime_create(struct kvm *kvm);
> +
> +int pvtime_create(struct kvm *kvm)
> +{
> +	int err;
> +	u64 lpt_paddr = 0x10000000;
> +	u64 st_paddr = lpt_paddr + 4096;
> +	u32 frequency = 100 * 1000 * 1000;
> +
> +	printf("lpt_paddr=%llx\n", lpt_paddr);
> +
> +	struct kvm_create_device pvtime_device = {
> +		.type = KVM_DEV_TYPE_ARM_PV_TIME,
> +		.flags = 0,
> +	};
> +
> +	err = ioctl(kvm->vm_fd, KVM_CREATE_DEVICE, &pvtime_device);
> +	if (err) {
> +		printf("Failed to create PV device\n");
> +		return 0;
> +	}
> +
> +	pvtime_fd = pvtime_device.fd;
> +
> +	struct kvm_device_attr lpt_base = {
> +		.group = KVM_DEV_ARM_PV_TIME_PADDR,
> +		.attr = KVM_DEV_ARM_PV_TIME_LPT,
> +		.addr = (u64)(unsigned long)&lpt_paddr
> +	};
> +	struct kvm_device_attr st_base = {
> +		.group = KVM_DEV_ARM_PV_TIME_PADDR,
> +		.attr = KVM_DEV_ARM_PV_TIME_ST,
> +		.addr = (u64)(unsigned long)&st_paddr
> +	};
> +
> +	struct kvm_device_attr lpt_freq = {
> +		.group = KVM_DEV_ARM_PV_TIME_FREQUENCY,
> +		.attr = KVM_DEV_ARM_PV_TIME_LPT,
> +		.addr = (u64)(unsigned long)&frequency
> +	};
> +
> +	err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_base);
> +	if (err) {
> +		perror("ioctl lpt_base failed");
> +		printf("Ignoring LPT...\n");
> +	}
> +	err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &st_base);
> +	if (err) {
> +		perror("ioctl st_base failed");
> +		goto out_err;
> +	}
> +	err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_freq);
> +	if (err) {
> +		perror("ioctl lpt_freq failed");
> +		printf("Ignoring LPT...\n");
> +	}
> +
> +	printf("PV time setup\n");
> +
> +	return 0;
> +out_err:
> +	close(pvtime_fd);
> +	return err;
> +}