Re: [PATCH v7 3/4] xen/riscv: panic if the device tree advertises neither Svade nor Svadu

[Zhang Zheng <zhangzheng@xxxxxxxxxxx>]

On Fri, 16 Oct 2026 17:34:19 +0200, Baptiste Le Duc 
<baptiste.le-duc@xxxxxxxxxx> wrote:
> p2m_set_pte_flags() presets the A/D bits of G-stage PTEs only when
> RISCV_ISA_EXT_svade is set, which is correct only if the device tree is.
> 
> The privileged spec allows exactly two schemes for updating the PTE A and D
> bits: hardware sets them on access and on write, or accessing a page whose
> A and/or D bit is clear raises a page fault so that software can set them
> (ratified as Svade). Every implementation uses one of them, but platforms
> designed before Svade and Svadu were ratified, such as the HiFive Premier
> P550, may advertise neither. Xen then cannot tell which scheme is in
> effect, so rather than guess, panic in riscv_fill_hwcap() when the device
> tree advertises neither Svade nor Svadu, so that the device tree gets
> fixed.
> 
> [...]

Tested-by: Zhang Zheng <zhangzheng@xxxxxxxxxxx>

-- 
Zhang Zheng <zhangzheng@xxxxxxxxxxx>