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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id v12-20020a5d4a4c000000b001e68ba61747sm11187250wrs.16.2022.03.13.09.07.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Mar 2022 09:07:38 -0700 (PDT) Date: Sun, 13 Mar 2022 16:07:37 +0000 From: Sebastian Ene To: Alexandru Elisei Cc: kvm@vger.kernel.org, qperret@google.com, will@kernel.org, julien.thierry.kdev@gmail.com, maz@kernel.org Subject: Re: [PATCH kvmtool v10 2/3] aarch64: Add stolen time support Message-ID: References: <20220309133422.2432649-1-sebastianene@google.com> <20220309133422.2432649-3-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, Mar 11, 2022 at 11:18:55AM +0000, Alexandru Elisei wrote: > Hi, > Hi, > On Wed, Mar 09, 2022 at 01:34:23PM +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/aarch32/include/kvm/kvm-cpu-arch.h | 5 ++ > > arm/aarch64/arm-cpu.c | 2 +- > > arm/aarch64/include/kvm/kvm-cpu-arch.h | 2 + > > arm/aarch64/pvtime.c | 96 ++++++++++++++++++++++++++ > > arm/include/arm-common/kvm-arch.h | 6 +- > > arm/kvm-cpu.c | 1 + > > include/kvm/kvm-config.h | 1 + > > 8 files changed, 112 insertions(+), 2 deletions(-) > > 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/aarch32/include/kvm/kvm-cpu-arch.h b/arm/aarch32/include/kvm/kvm-cpu-arch.h > > index 780e0e2..6fe0206 100644 > > --- a/arm/aarch32/include/kvm/kvm-cpu-arch.h > > +++ b/arm/aarch32/include/kvm/kvm-cpu-arch.h > > @@ -20,4 +20,9 @@ static inline int kvm_cpu__configure_features(struct kvm_cpu *vcpu) > > return 0; > > } > > > > +static inline int kvm_cpu__teardown_pvtime(struct kvm *kvm) > > +{ > > + return 0; > > +} > > + > > #endif /* KVM__KVM_CPU_ARCH_H */ > > diff --git a/arm/aarch64/arm-cpu.c b/arm/aarch64/arm-cpu.c > > index d7572b7..7e4a3c1 100644 > > --- a/arm/aarch64/arm-cpu.c > > +++ b/arm/aarch64/arm-cpu.c > > @@ -22,7 +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; > > - return 0; > > + return kvm_cpu__setup_pvtime(vcpu); > > } > > > > static struct kvm_arm_target target_generic_v8 = { > > diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h b/arm/aarch64/include/kvm/kvm-cpu-arch.h > > index 8dfb82e..35996dc 100644 > > --- a/arm/aarch64/include/kvm/kvm-cpu-arch.h > > +++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h > > @@ -19,5 +19,7 @@ > > > > void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init *init); > > int kvm_cpu__configure_features(struct kvm_cpu *vcpu); > > +int kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu); > > +int kvm_cpu__teardown_pvtime(struct kvm *kvm); > > > > #endif /* KVM__KVM_CPU_ARCH_H */ > > diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c > > new file mode 100644 > > index 0000000..720e9de > > --- /dev/null > > +++ b/arm/aarch64/pvtime.c > > @@ -0,0 +1,96 @@ > > +#include "kvm/kvm.h" > > +#include "kvm/kvm-cpu.h" > > +#include "kvm/util.h" > > + > > +#include > > +#include > > + > > +#define ARM_PVTIME_STRUCT_SIZE (64) > > + > > +static void *usr_mem; > > + > > +static int pvtime__alloc_region(struct kvm *kvm) > > +{ > > + char *mem; > > + int ret = 0; > > + > > + mem = mmap(NULL, ARM_PVTIME_BASE, PROT_RW, > > + MAP_ANON_NORESERVE, -1, 0); > > + if (mem == MAP_FAILED) > > + return -errno; > > + > > + ret = kvm__register_ram(kvm, ARM_PVTIME_BASE, > > + ARM_PVTIME_BASE, mem); > > + if (ret) { > > + munmap(mem, ARM_PVTIME_BASE); > > + return ret; > > + } > > + > > + usr_mem = mem; > > + return ret; > > +} > > + > > +static int pvtime__teardown_region(struct kvm *kvm) > > +{ > > + if (usr_mem == NULL) > > + return 0; > > + > > + kvm__destroy_mem(kvm, ARM_PVTIME_BASE, > > + ARM_PVTIME_BASE, usr_mem); > > + munmap(usr_mem, ARM_PVTIME_BASE); > > + usr_mem = NULL; > > + return 0; > > +} > > + > > +int kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu) > > +{ > > + int ret; > > + bool has_stolen_time; > > + u64 pvtime_guest_addr = ARM_PVTIME_BASE + vcpu->cpu_id * > > + 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, > > + .attr = KVM_ARM_VCPU_PVTIME_IPA > > + }; > > + > > + kvm_cfg = &vcpu->kvm->cfg; > > + if (kvm_cfg->no_pvtime) > > + return 0; > > + > > + has_stolen_time = kvm__supports_extension(vcpu->kvm, > > + KVM_CAP_STEAL_TIME); > > + if (!has_stolen_time) { > > + kvm_cfg->no_pvtime = true; > > + return 0; > > + } > > + > > + ret = ioctl(vcpu->vcpu_fd, KVM_HAS_DEVICE_ATTR, &pvtime_attr); > > + if (ret) { > > + perror("KVM_HAS_DEVICE_ATTR failed\n"); > > + goto out_err; > > Nitpick: here we return -1 (ioctl() return value when it fails) instead of > returning -errno. You can set ret = -errno before the perror() call (in > case it also fails for some reason, thus changing the value of errno). > > Not a big deal, but it changes the semantics of the return value for the > function: below, for pvtime__alloc_region() we return -errno, but here we > return -1. Someone who is debugging an error might print this return value > and think that the ioctl() failed with error code EPERM (EPERM is 1), which > is not a valid error code for ioctl() according to man 2 ioctl. It will > also look rather strange for the perror to print the error message > associated with a different error code than the error code that is returned > from this function. > I will update the return code, thanks for the suggestion. > > + } > > + > > + if (!usr_mem) { > > + ret = pvtime__alloc_region(vcpu->kvm); > > + if (ret) { > > + perror("Failed allocating pvtime region\n"); > > + goto out_err; > > + } > > + } > > + > > + pvtime_attr.addr = (u64)&pvtime_guest_addr; > > + ret = ioctl(vcpu->vcpu_fd, KVM_SET_DEVICE_ATTR, &pvtime_attr); > > + if (!ret) > > + return 0; > > Nitpick: same here, ret must be set to -errno before returning. > Right, I will set it to errno on 'ret != 0'. > > + > > + perror("KVM_SET_DEVICE_ATTR failed\n"); > > + pvtime__teardown_region(vcpu->kvm); > > +out_err: > > + return ret; > > +} > > + > > +int kvm_cpu__teardown_pvtime(struct kvm *kvm) > > +{ > > + return pvtime__teardown_region(kvm); > > +} > > diff --git a/arm/include/arm-common/kvm-arch.h b/arm/include/arm-common/kvm-arch.h > > index c645ac0..43b1f77 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_BASE (ARM_RTC_MMIO_BASE + ARM_RTC_MMIO_SIZE) > > +#define ARM_PVTIME_SIZE SZ_64K > > + > > #define KVM_FLASH_MMIO_BASE (ARM_MMIO_AREA + 0x1000000) > > #define KVM_FLASH_MAX_SIZE 0x1000000 > > > > diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c > > index 84ac1e9..00660d6 100644 > > --- a/arm/kvm-cpu.c > > +++ b/arm/kvm-cpu.c > > @@ -144,6 +144,7 @@ void kvm_cpu__arch_nmi(struct kvm_cpu *cpu) > > > > void kvm_cpu__delete(struct kvm_cpu *vcpu) > > { > > + kvm_cpu__teardown_pvtime(vcpu->kvm); > > free(vcpu); > > } > > > > 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 > > -- > > Tested the series, a guest is able to detect pvtime: > > [ 0.008661] arm-pv: using stolen time PV > Thanks for the review and for testing this, > Tested-by: Alexandru Elisei > > With the two nitpicks above fixed, the patch looks correct to me: > > Reviewed-by: Alexandru Elisei > > Thanks, > Alex Cheers, Sebastian