From: Andrew Jones <ajones@ventanamicro.com>
To: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Cc: qemu-devel@nongnu.org, qemu-riscv@nongnu.org,
alistair.francis@wdc.com, bmeng@tinylab.org,
liweiwei@iscas.ac.cn, zhiwei_liu@linux.alibaba.com,
palmer@rivosinc.com
Subject: Re: [PATCH v3 12/19] target/riscv: add KVM specific MISA properties
Date: Mon, 26 Jun 2023 08:24:47 +0200 [thread overview]
Message-ID: <20230626-b5e6933676608436b6558fc4@orel> (raw)
In-Reply-To: <20230622135700.105383-13-dbarboza@ventanamicro.com>
On Thu, Jun 22, 2023 at 10:56:53AM -0300, Daniel Henrique Barboza wrote:
> Using all TCG user properties in KVM is tricky. First because KVM
> supports only a small subset of what TCG provides, so most of the
> cpu->cfg flags do nothing for KVM.
>
> Second, and more important, we don't have a way of telling if any given
> value is an user input or not. For TCG this has a small impact since we
> just validating everything and error out if needed. But for KVM it would
> be good to know if a given value was set by the user or if it's a value
> already provided by KVM. Otherwise we don't know how to handle failed
> kvm_set_one_regs() when writing the configurations back.
>
> These characteristics make it overly complicated to use the same user
> facing flags for both KVM and TCG. A simpler approach is to create KVM
> specific properties that have specialized logic, forking KVM and TCG use
> cases for those cases only. Fully separating KVM/TCG properties is
> unneeded at this point - in fact we want the user experience to be as
> equal as possible, regardless of the acceleration chosen.
>
> We'll start this fork with the MISA properties, adding the MISA bits
> that the KVM driver currently supports. A new KVMCPUConfig type is
> introduced. It'll hold general information about an extension. For MISA
> extensions we're going to use the newly created misa_ext_infos[] to
> populate their name and description. 'offset' holds the MISA bit (RVA,
> RVC, ...). We're calling it 'offset' instead of 'misa_bit' because this
> same KVMCPUConfig struct will be used to multi-letter extensions later
> on.
>
> This new type also holds a 'user_set' flag. This flag will be set when
> the user set an option that's different than what is already configured
> in the host, requiring KVM intervention to write the regs back during
> kvm_arch_init_vcpu(). Similar mechanics will be implemented for
> multi-letter extensions as well.
>
> There is no need to duplicate more code than necessary, so we're going
> to use the existing kvm_riscv_init_user_properties() to add the KVM
> specific properties. Any code that is adding a TCG user prop is then
> changed slightly to verify first if there's a KVM prop with the same
> name already added.
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
> target/riscv/cpu.c | 10 ++++++
> target/riscv/kvm.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 88 insertions(+)
>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
next prev parent reply other threads:[~2023-06-26 6:26 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-22 13:56 [PATCH v3 00/19] target/riscv, KVM: fixes and enhancements Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 01/19] target/riscv: skip features setup for KVM CPUs Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 02/19] hw/riscv/virt.c: skip 'mmu-type' FDT if satp mode not set Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 03/19] target/riscv/cpu.c: restrict 'mvendorid' value Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 04/19] target/riscv/cpu.c: restrict 'mimpid' value Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 05/19] target/riscv/cpu.c: restrict 'marchid' value Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 06/19] target/riscv: use KVM scratch CPUs to init KVM properties Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 07/19] target/riscv: read marchid/mimpid in kvm_riscv_init_machine_ids() Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 08/19] target/riscv: handle mvendorid/marchid/mimpid for KVM CPUs Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 09/19] linux-headers: Update to v6.4-rc1 Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 10/19] target/riscv/kvm.c: init 'misa_ext_mask' with scratch CPU Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 11/19] target/riscv/cpu: add misa_ext_info_arr[] Daniel Henrique Barboza
2023-06-23 9:30 ` Andrew Jones
2023-06-22 13:56 ` [PATCH v3 12/19] target/riscv: add KVM specific MISA properties Daniel Henrique Barboza
2023-06-23 9:38 ` Andrew Jones
2023-06-23 14:14 ` Daniel Henrique Barboza
2023-06-24 7:32 ` Andrew Jones
2023-06-25 22:38 ` Daniel Henrique Barboza
2023-06-26 6:24 ` Andrew Jones [this message]
2023-06-22 13:56 ` [PATCH v3 13/19] target/riscv/kvm.c: update KVM MISA bits Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 14/19] target/riscv/kvm.c: add multi-letter extension KVM properties Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 15/19] target/riscv/cpu.c: remove priv_ver check from riscv_isa_string_ext() Daniel Henrique Barboza
2023-06-23 9:46 ` Andrew Jones
2023-06-22 13:56 ` [PATCH v3 16/19] target/riscv/cpu.c: create KVM mock properties Daniel Henrique Barboza
2023-06-23 9:58 ` Andrew Jones
2023-06-23 14:28 ` Daniel Henrique Barboza
2023-06-24 7:41 ` Andrew Jones
2023-06-26 17:27 ` Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 17/19] target/riscv: update multi-letter extension KVM properties Daniel Henrique Barboza
2023-06-22 13:56 ` [PATCH v3 18/19] target/riscv/kvm.c: add kvmconfig_get_cfg_addr() helper Daniel Henrique Barboza
2023-06-22 13:57 ` [PATCH v3 19/19] target/riscv/kvm.c: read/write (cbom|cboz)_blocksize in KVM Daniel Henrique Barboza
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