Re: [PATCH v3 1/3] lib: sbi: Add RISC-V vector context save/restore support

From: "Radim Krčmář" <radim.krcmar@oss.qualcomm.com>
To: <dave.patel@riscstar.com>, "Samuel Holland" <samuel.holland@sifive.com>
Cc: "Scott Bambrough" <scott@riscstar.com>,
	"Robin Randhawa" <robin.randhawa@sifive.com>,
	"Anup Patel" <anup.patel@qti.qualcomm.com>,
	"Ray Mao" <raymond.mao@riscstar.com>,
	"Anup Patel" <anuppate@qti.qualcomm.com>,
	"Dhaval" <dhaval@rivosinc.com>,
	"Peter Lin" <peter.lin@sifive.com>, <opensbi@lists.infradead.org>,
	"opensbi" <opensbi-bounces@lists.infradead.org>
Subject: Re: [PATCH v3 1/3] lib: sbi: Add RISC-V vector context save/restore support
Date: Thu, 02 Apr 2026 15:35:05 +0200	[thread overview]
Message-ID: <DHIPIKMRJ56H.UTR2JQR6X23E@oss.qualcomm.com> (raw)
In-Reply-To: <20260331055858.305207-2-dave.patel@riscstar.com>

2026-03-31T06:58:55+01:00, <dave.patel@riscstar.com>:
> From: Dave Patel <dave.patel@riscstar.com>
>
> Eager context switch: Add support for saving and restoring RISC-V vector
> extension state in OpenSBI. This introduces a per-hart vector context
> structure and helper routines to perform full context save and restore.
>
> The vector context includes vl, vtype, vcsr CSRs along with storage for all
> 32 vector registers. The register state is saved and restored using byte-wise
> vector load/store instructions (vse8.v/vle8.v), making the implementation
> independent of current SEW/LMUL configuration.
>
> The implementation follows an eager context switching model where the entire
> vector state is saved and restored on every context switch. This provides a
> simple and deterministic mechanism without requiring lazy trap-based
> management.
>
> Notes:
> - The SBI_MAX_VLENB is configured using CONFIG_SBI_MAX_VLENB.
>
> Signed-off-by: Dave Patel <dave.patel@riscstar.com>
> ---

You missed my comment on [v2 1/3]:
https://lore.kernel.org/opensbi/DHG4IUERGFUV.3TT9CFPZ9YEDG@qti.qualcomm.com/

The two points are:
1. Possible cross-domain data access.
2. Writes to read-only CSRs.

Thanks.

-- 
opensbi mailing list
opensbi@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/opensbi