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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id l12sm53801683wrs.11.2022.02.23.01.41.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Feb 2022 01:41:30 -0800 (PST) Date: Wed, 23 Feb 2022 09:41:28 +0000 From: Sebastian Ene To: Andre Przywara Subject: Re: [PATCH kvmtool v3] aarch64: Add stolen time support Message-ID: References: <2772b40f99a30ecd475fa83641d40994@kernel.org> <20220222171558.1a77d501@donnerap.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220222171558.1a77d501@donnerap.cambridge.arm.com> Cc: maz@kernel.org, will@kernel.org, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, Feb 22, 2022 at 05:15:57PM +0000, Andre Przywara wrote: > On Tue, 22 Feb 2022 14:50:56 +0000 > Alexandru Elisei wrote: > > > Hi, > > > > On Tue, Feb 22, 2022 at 02:35:24PM +0000, Marc Zyngier wrote: > > > On 2022-02-22 14:28, Alexandru Elisei wrote: > > > > Hi, > > > > > > > > On Tue, Feb 22, 2022 at 02:18:40PM +0000, Marc Zyngier wrote: > > > > > On 2022-02-22 13:58, Alexandru Elisei wrote: > > > > > > Hi, > > > > > > > > > > > > On Tue, Feb 22, 2022 at 10:08:30AM +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. The exact format of the structure stored by the > > > > > > > hypervisor is described in the ARM DEN0057A document. > > > > > > > > > > > > > > Signed-off-by: Sebastian Ene > > > > > > > --- > > > > > > > Changelog since v2: > > > > > > > - Moved the AARCH64_PVTIME_* definitions from arm-common/kvm-arch.h > > > > > > > to > > > > > > > arm64/pvtime.c as pvtime is only available for arm64. > > > > > > > > > > > > > > Changelog since v1: > > > > > > > - Removed the pvtime.h header file and moved the definitions to > > > > > > > kvm-cpu-arch.h > > > > > > > Verified if the stolen time capability is supported before > > > > > > > allocating > > > > > > > and mapping the memory. > > > > > > > > > > > > > > Makefile | 1 + > > > > > > > arm/aarch64/arm-cpu.c | 1 + > > > > > > > arm/aarch64/include/kvm/kvm-cpu-arch.h | 1 + > > > > > > > arm/aarch64/pvtime.c | 89 > > > > > > > ++++++++++++++++++++++++++ > > > > > > > arm/kvm-cpu.c | 14 ++-- > > > > > > > 5 files changed, 99 insertions(+), 7 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/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..247e4f3 > > > > > > > --- /dev/null > > > > > > > +++ b/arm/aarch64/pvtime.c > > > > > > > @@ -0,0 +1,89 @@ > > > > > > > +#include "kvm/kvm.h" > > > > > > > +#include "kvm/kvm-cpu.h" > > > > > > > +#include "kvm/util.h" > > > > > > > + > > > > > > > +#include > > > > > > > +#include > > > > > > > + > > > > > > > +#define AARCH64_PVTIME_IPA_MAX_SIZE SZ_64K > > > > > > > +#define AARCH64_PVTIME_IPA_START (ARM_MEMORY_AREA - \ > > > > > > > + AARCH64_PVTIME_IPA_MAX_SIZE) > > > > > > > > > > > > This doesn't change the fact that it overlaps with KVM_PCI_MMIO_AREA, > > > > > > which is > > > > > > exposed to the guest in the DTB (see my reply to v2). > > > > > > > > > > Yup, this is a bit of a problem, and overlapping regions are > > > > > a big no-no. Why can't the pvtime region be dynamically placed > > > > > after the RAM (after checking that there is enough space to > > > > > register it in the IPA space)? > > > > > > > > In theory, is there something to stop someone from creating a VM with > > > > enough > > > > memory to reach the end of the IPA space? > > > > > > No, but we can either steal 64kB from that upper limit if that's the > > > case, or let the user know that stolen time is disabled because they > > > have been greedy... > > > > If we decide to go with having the pvtime region after RAM, I would prefer to > > disable it if there's no room, and print a big warning letting the user know > > what is happening and why, instead of silently shrinking the memory size > > specified by the user. > > > > I've CC'ed Andre, he's the last one who made changes to the memory layout when > > he added the flash device. Hi, > > Why don't we just put that inside the MMIO "region", so after the RTC, for > instance? This is in a separate memslot anyway, and there is plenty of > space there for a 64K page. > I'd just add some lines to arm/include/arm-common/kvm-arch.h to that > effect. > I think that should work, thanks for the suggestion. > Cheers, > Andre Thanks, Sebastian _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm