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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id m21-20020a05600c4f5500b0037d342db78asm6096410wmq.35.2022.02.25.05.21.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Feb 2022 05:21:27 -0800 (PST) Date: Fri, 25 Feb 2022 13:21:26 +0000 From: Sebastian Ene To: Alexandru Elisei Cc: kvm@vger.kernel.org, qperret@google.com, maz@kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org, julien.thierry.kdev@gmail.com Subject: Re: [PATCH kvmtool v4 1/3] aarch64: Add stolen time support Message-ID: References: <20220224165103.1157358-1-sebastianene@google.com> <20220224165103.1157358-2-sebastianene@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Feb 25, 2022 at 11:55:03AM +0000, Alexandru Elisei wrote: > Hi, > Hi, > On Thu, Feb 24, 2022 at 04:51:03PM +0000, Sebastian Ene wrote: > > This patch adds support for stolen time by sharing a memory region > > with the guest which will be used by the hypervisor to store the stolen > > time information. Reserve a 64kb MMIO memory region after the RTC peripheral > > to be used by pvtime. The exact format of the structure stored by the > > hypervisor is described in the ARM DEN0057A document. > > > > Signed-off-by: Sebastian Ene > > --- > > Makefile | 1 + > > arm/aarch64/arm-cpu.c | 1 + > > arm/aarch64/include/kvm/kvm-cpu-arch.h | 1 + > > arm/aarch64/pvtime.c | 94 ++++++++++++++++++++++++++ > > arm/include/arm-common/kvm-arch.h | 6 +- > > include/kvm/kvm-config.h | 1 + > > 6 files changed, 103 insertions(+), 1 deletion(-) > > create mode 100644 arm/aarch64/pvtime.c > > > > diff --git a/Makefile b/Makefile > > index f251147..e9121dc 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -182,6 +182,7 @@ ifeq ($(ARCH), arm64) > > OBJS += arm/aarch64/arm-cpu.o > > OBJS += arm/aarch64/kvm-cpu.o > > OBJS += arm/aarch64/kvm.o > > + OBJS += arm/aarch64/pvtime.o > > ARCH_INCLUDE := $(HDRS_ARM_COMMON) > > ARCH_INCLUDE += -Iarm/aarch64/include > > > > diff --git a/arm/aarch64/arm-cpu.c b/arm/aarch64/arm-cpu.c > > index d7572b7..326fb20 100644 > > --- a/arm/aarch64/arm-cpu.c > > +++ b/arm/aarch64/arm-cpu.c > > @@ -22,6 +22,7 @@ static void generate_fdt_nodes(void *fdt, struct kvm *kvm) > > static int arm_cpu__vcpu_init(struct kvm_cpu *vcpu) > > { > > vcpu->generate_fdt_nodes = generate_fdt_nodes; > > + kvm_cpu__setup_pvtime(vcpu); > > return 0; > > } > > > > diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h b/arm/aarch64/include/kvm/kvm-cpu-arch.h > > index 8dfb82e..b57d6e6 100644 > > --- a/arm/aarch64/include/kvm/kvm-cpu-arch.h > > +++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h > > @@ -19,5 +19,6 @@ > > > > void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init *init); > > int kvm_cpu__configure_features(struct kvm_cpu *vcpu); > > +void kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu); > > > > #endif /* KVM__KVM_CPU_ARCH_H */ > > diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c > > new file mode 100644 > > index 0000000..8251f6a > > --- /dev/null > > +++ b/arm/aarch64/pvtime.c > > @@ -0,0 +1,94 @@ > > +#include "kvm/kvm.h" > > +#include "kvm/kvm-cpu.h" > > +#include "kvm/util.h" > > + > > +#include > > +#include > > + > > +#define ARM_PVTIME_STRUCT_SIZE (64) > > + > > +struct pvtime_data_priv { > > + bool is_supported; > > + char *usr_mem; > > +}; > > + > > +static struct pvtime_data_priv pvtime_data = { > > + .is_supported = true, > > + .usr_mem = NULL > > +}; > > + > > +static int pvtime__alloc_region(struct kvm *kvm) > > +{ > > + char *mem; > > + int ret = 0; > > + > > + mem = mmap(NULL, ARM_PVTIME_MMIO_SIZE, PROT_RW, > > + MAP_ANON_NORESERVE, -1, 0); > > + if (mem == MAP_FAILED) > > + return -ENOMEM; > > Hm... man 2 mmap lists a few dozen error codes, why use -ENOMEM here instead of > -errno? This just makes debugging harder. > I will return the -errno error code here. > > + > > + ret = kvm__register_dev_mem(kvm, ARM_PVTIME_MMIO_BASE, > > + ARM_PVTIME_MMIO_SIZE, mem); > > + if (ret) { > > + munmap(mem, ARM_PVTIME_MMIO_SIZE); > > + return ret; > > + } > > + > > + pvtime_data.usr_mem = mem; > > + return ret; > > +} > > + > > +static int pvtime__teardown_region(struct kvm *kvm) > > +{ > > + if (pvtime_data.usr_mem == NULL) > > + return 0; > > + > > + kvm__destroy_mem(kvm, ARM_PVTIME_MMIO_BASE, > > + ARM_PVTIME_MMIO_SIZE, pvtime_data.usr_mem); > > + munmap(pvtime_data.usr_mem, ARM_PVTIME_MMIO_SIZE); > > + pvtime_data.usr_mem = NULL; > > + return 0; > > +} > > + > > +void kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu) > > +{ > > + int ret; > > + u64 pvtime_guest_addr = ARM_PVTIME_MMIO_BASE + vcpu->cpu_id * > > That's trange, cpu_id is not initialized here because target->init() is called > before setting up the cpu_id. The following patch in the series, "aarch64: > Populate the vCPU struct before target->init()" should come before this one. > > > + ARM_PVTIME_STRUCT_SIZE; > > + struct kvm_config *kvm_cfg = NULL; > > + struct kvm_device_attr pvtime_attr = (struct kvm_device_attr) { > > + .group = KVM_ARM_VCPU_PVTIME_CTRL, > > + .addr = KVM_ARM_VCPU_PVTIME_IPA > > + }; > > + > > + BUG_ON(!vcpu); > > + BUG_ON(!vcpu->kvm); > > + > > + kvm_cfg = &vcpu->kvm->cfg; > > + if (kvm_cfg && kvm_cfg->no_pvtime) > > If you move the next patch in the series before this one, all the above checks > will not be needed and should be removed. > > In general, each patch in a series should be able to build properly and run a VM > without errors. This is to help users when bisecting [1]. If I build kvmtool > from this patch and I try to run a VM I get the error: > > Error: BUG at arm/aarch64/pvtime.c:65 > > [1] https://github.com/torvalds/linux/blob/master/Documentation/process/submitting-patches.rst#separate-your-changes > I will move the patch that handles the structure initialisation before this one and I will remove those checks. Thanks for the suggestion ! > > + return; > > + > > + if (!pvtime_data.is_supported) > > + return; > > + > > + ret = ioctl(vcpu->vcpu_fd, KVM_HAS_DEVICE_ATTR, &pvtime_attr); > > + if (ret) > > + goto out_err; > > You should check that pvtime is supported by checking the KVM_CAP_STEAL_TIME on > the VM fd, as that's how capabilities are advertised by KVM. > I thought that it is sufficient to verify that it has the device attributes for *PVTIME. I will add this check too, thanks for the suggestion ! > > + > > + if (!pvtime_data.usr_mem) { > > + ret = pvtime__alloc_region(vcpu->kvm); > > pvtime__alloc_region() can fail pretty catastrophically, is it ok to ignore it > and go on? I would have expected kvm_cpu__setup_pvtime() to return an error > which is then propagated to target->init(). > Hmm, I didn't propagate the error code from kvm_cpu__setup_pvtime() because if this feature is not supported it will hit:"Unable to initialise vcpu". But I guess that now we can propagate the error code as we have '--no-pvtime' command argument. What do you think ? > > + if (ret) > > + goto out_err; > > + } > > + > > + pvtime_attr.addr = (u64)&pvtime_guest_addr; > > + ret = ioctl(vcpu->vcpu_fd, KVM_SET_DEVICE_ATTR, &pvtime_attr); > > + if (!ret) > > + return; > > + > > + pvtime__teardown_region(vcpu->kvm); > > +out_err: > > + pvtime_data.is_supported = false; > > +} > > + > > +dev_exit(pvtime__teardown_region); > > It is customary to put the dev_exit() exactly after the function it refers to. > I will move this. > > diff --git a/arm/include/arm-common/kvm-arch.h b/arm/include/arm-common/kvm-arch.h > > index c645ac0..3f82663 100644 > > --- a/arm/include/arm-common/kvm-arch.h > > +++ b/arm/include/arm-common/kvm-arch.h > > @@ -15,7 +15,8 @@ > > * | PCI |////| plat | | | | | > > * | I/O |////| MMIO: | Flash | virtio | GIC | PCI | DRAM > > * | space |////| UART, | | MMIO | | (AXI) | > > - * | |////| RTC | | | | | > > + * | |////| RTC, | | | | | > > + * | |////| PVTIME| | | | | > > * +-------+----+-------+-------+--------+-----+---------+---...... > > */ > > > > @@ -34,6 +35,9 @@ > > #define ARM_RTC_MMIO_BASE (ARM_UART_MMIO_BASE + ARM_UART_MMIO_SIZE) > > #define ARM_RTC_MMIO_SIZE 0x10000 > > > > +#define ARM_PVTIME_MMIO_BASE (ARM_RTC_MMIO_BASE + ARM_RTC_MMIO_SIZE) > > +#define ARM_PVTIME_MMIO_SIZE SZ_64K > > This looks good. > > Thanks, > Alex > Thanks for the review, Sebastian > > + > > #define KVM_FLASH_MMIO_BASE (ARM_MMIO_AREA + 0x1000000) > > #define KVM_FLASH_MAX_SIZE 0x1000000 > > > > diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h > > index 6a5720c..48adf27 100644 > > --- a/include/kvm/kvm-config.h > > +++ b/include/kvm/kvm-config.h > > @@ -62,6 +62,7 @@ struct kvm_config { > > bool no_dhcp; > > bool ioport_debug; > > bool mmio_debug; > > + bool no_pvtime; > > }; > > > > #endif > > -- > > 2.35.1.473.g83b2b277ed-goog > > > > _______________________________________________ > > kvmarm mailing list > > kvmarm@lists.cs.columbia.edu > > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm