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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v4 1/1] xen/riscv: add RISC-V virtual SBI base extension support for guests
Hello,
Le 30/12/2025 à 16:52, Oleksii Kurochko a écrit :
> Add support of virtual SBI base extension calls for RISC-V guests, delegating
> hardware-specific queries to the underlying SBI and handling version and
> firmware ID queries directly.
>
> The changes include:
> 1. Define new SBI base extension function IDs (SBI_EXT_BASE_GET_MVENDORID,
> SBI_EXT_BASE_GET_MARCHID, SBI_EXT_BASE_GET_MIMPID).
> 2. Introduce XEN_SBI_VER_MAJOR, XEN_SBI_VER_MINOR for imeplenataion of
> SBI_EXT_BASE_GET_SPEC_VERSION.
> 4. Introduce SBI_XEN_IMPID to implement SBI_EXT_BASE_GET_IMP_ID.
> 5. Implement handling of SBI base extension functions, including version,
> firmware ID, and machine-specific queries.
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
> Changes in v4:
> - Move definition of XEN_SBI_VER_{MAJOR, MINOR} to base-extension.c.
> - Correct string format for FID: s/#%#lx/#%lu.
> - Print first EID then FID (as vsbi/core.c code does).
> ---
> Changes in v3:
> - s/XEN_SBI_IMPID/SBI_XEN_IMPID
> - Add ASSERT(eid == SBI_EXT_BASE) in vsbi_base_ecall_handler().
> - Fix code style for switch/case.
> - Use current instead of `vcpu` argument as it was dropped from
> vsbi_base_ecall_handler() prototype.
> - Add comments for define-s XEN_SBI_VER_{MAJOR, MINOR} and SBI_XEN_IMPID.
> ---
> Changes in v2:
> - s/vsbi-base-extension.*/base-extension.*
> - Introduce VCPU_SBI_IMPID, XEN_SBI_VER_MINOR and XEN_SBI_VER_MAJOR.
> - Return VCPU_SBI_IMPID in the case of SBI_EXT_BASE_GET_IMP_ID.
> - Return Xen version in the case of SBI_EXT_BASE_GET_IMP_VERSION.
> - Use domain_crash() instead of panic() for default case.
> - For SBI_EXT_BASE_GET_{MVENDORID,MARCHID,MIMPID} abd SBI_EXT_BASE_PROBE_EXT
> add handling of a domain is h/w or not.
> ---
> xen/arch/riscv/include/asm/sbi.h | 6 ++
> xen/arch/riscv/vsbi/Makefile | 1 +
> xen/arch/riscv/vsbi/base-extension.c | 82 ++++++++++++++++++++++++++++
> 3 files changed, 89 insertions(+)
> create mode 100644 xen/arch/riscv/vsbi/base-extension.c
>
> diff --git a/xen/arch/riscv/include/asm/sbi.h
> b/xen/arch/riscv/include/asm/sbi.h
> index 751bae6d6654..79f7ff5c5501 100644
> --- a/xen/arch/riscv/include/asm/sbi.h
> +++ b/xen/arch/riscv/include/asm/sbi.h
> @@ -14,6 +14,9 @@
>
> #include <xen/cpumask.h>
>
> +/* SBI-defined implementation ID */
> +#define SBI_XEN_IMPID 7
> +
> #define SBI_EXT_0_1_SET_TIMER 0x0
> #define SBI_EXT_0_1_CONSOLE_PUTCHAR 0x1
> #define SBI_EXT_0_1_CONSOLE_GETCHAR 0x2
> @@ -32,6 +35,9 @@
> #define SBI_EXT_BASE_GET_IMP_ID 0x1
> #define SBI_EXT_BASE_GET_IMP_VERSION 0x2
> #define SBI_EXT_BASE_PROBE_EXT 0x3
> +#define SBI_EXT_BASE_GET_MVENDORID 0x4
> +#define SBI_EXT_BASE_GET_MARCHID 0x5
> +#define SBI_EXT_BASE_GET_MIMPID 0x6
>
> /* SBI function IDs for RFENCE extension */
> #define SBI_EXT_RFENCE_REMOTE_FENCE_I 0x0
> diff --git a/xen/arch/riscv/vsbi/Makefile b/xen/arch/riscv/vsbi/Makefile
> index bc5755cb13d6..8ce470f787c5 100644
> --- a/xen/arch/riscv/vsbi/Makefile
> +++ b/xen/arch/riscv/vsbi/Makefile
> @@ -1,2 +1,3 @@
> +obj-y += base-extension.o
> obj-y += core.o
> obj-y += legacy-extension.o
> diff --git a/xen/arch/riscv/vsbi/base-extension.c
> b/xen/arch/riscv/vsbi/base-extension.c
> new file mode 100644
> index 000000000000..41a95ae188dd
> --- /dev/null
> +++ b/xen/arch/riscv/vsbi/base-extension.c
> @@ -0,0 +1,82 @@
> +
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#include <xen/lib.h>
> +#include <xen/sched.h>
> +#include <xen/version.h>
> +
> +#include <asm/processor.h>
> +#include <asm/sbi.h>
> +#include <asm/vsbi.h>
> +
> +/* Xen-controlled SBI version reported to guests */
> +#define XEN_SBI_VER_MAJOR 0
> +#define XEN_SBI_VER_MINOR 2
> +
> +static int vsbi_base_ecall_handler(unsigned long eid, unsigned long fid,
> + struct cpu_user_regs *regs)
> +{
> + int ret = 0;
> + struct sbiret sbi_ret;
> +
> + ASSERT(eid == SBI_EXT_BASE);
> +
> + switch ( fid )
> + {
> + case SBI_EXT_BASE_GET_SPEC_VERSION:
> + regs->a1 = MASK_INSR(XEN_SBI_VER_MAJOR, SBI_SPEC_VERSION_MAJOR_MASK)
> |
> + XEN_SBI_VER_MINOR;
> + break;
> +
> + case SBI_EXT_BASE_GET_IMP_ID:
> + regs->a1 = SBI_XEN_IMPID;
> + break;
> +
> + case SBI_EXT_BASE_GET_IMP_VERSION:
> + regs->a1 = (xen_major_version() << 16) | xen_minor_version();
> + break;
> +
> + case SBI_EXT_BASE_GET_MVENDORID:
> + case SBI_EXT_BASE_GET_MARCHID:
> + case SBI_EXT_BASE_GET_MIMPID:
> + if ( is_hardware_domain(current->domain) )
> + {
> + sbi_ret = sbi_ecall(SBI_EXT_BASE, fid, 0, 0, 0, 0, 0, 0);
> + ret = sbi_ret.error;
> + regs->a1 = sbi_ret.value;
> + }
> + else
> + /*
> + * vSBI should present a consistent, virtualized view to guests.
> + * In particular, DomU-visible data must remain stable across
> + * migration and must not expose hardware-specific details.
> + *
> + * These register(s) must be readable in any implementation,
> + * but a value of 0 can be returned to indicate the field
> + * is not implemented.
> + */
> + regs->a1 = 0;
> +
> + break;
> +
> + case SBI_EXT_BASE_PROBE_EXT:
> + regs->a1 = vsbi_find_extension(regs->a0) ? 1 : 0;
> + break;
> +
> + default:
> + /*
> + * TODO: domain_crash() is acceptable here while things are still
> under
> + * development.
> + * It shouldn't stay like this in the end though: guests should not
> + * be punished like this for something Xen hasn't implemented.
> + */
> + domain_crash(current->domain,
> + "%s: Unsupported ecall: EID: #%#lx FID: #%lu\n",
> + __func__, eid, fid);
I think we should rather report "SBI_ERR_NOT_SUPPORTED" (-2) instead
(eventually logging a warning in Xen) ?
> + break;
> + }
> +
> + return ret;
> +}
> +
> +VSBI_EXT(base, SBI_EXT_BASE, SBI_EXT_BASE, vsbi_base_ecall_handler)
Teddy
--
Teddy Astie | Vates XCP-ng Developer
XCP-ng & Xen Orchestra - Vates solutions
web: https://vates.tech
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