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

Steven Price
2019-08-12T10:39:24Z

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.

----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;
+}