On 02.06.2025 21:17, dm...@proton.me wrote:
> From: Denis Mukhin <dmuk...@ford.com>
>
> Rewrite emulation_flags_ok() to simplify future modifications.
>
> No functional change intended.
>
> Signed-off-by: Denis Mukhin <dmuk...@ford.com>
> Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> Reviewed-by: Teddy Astie <teddy.as...@vates.tech>
> ---
> Changes since v4:
> - updated commentaries
> - added Teddy's R-b, kept Stefano's R-b
> ---
> xen/arch/x86/domain.c | 91 ++++++++++++++++++++++++++++++++++---------
> 1 file changed, 73 insertions(+), 18 deletions(-)
Given this diffstat, I wonder what the other x86 maintainers think about
this.
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -743,32 +743,87 @@ int arch_sanitise_domain_config(struct
> xen_domctl_createdomain *config)
> return 0;
> }
>
> +/*
> + * Verify that the domain's emulation flags resolve to a supported
> configuration.
> + *
> + * This ensures we only allow a known, safe subset of emulation combinations
> + * (for both functionality and security). Arbitrary mixes are likely to cause
> + * errors (e.g., null pointer dereferences).
> + *
> + * NB: use the internal X86_EMU_XXX symbols, not the public XEN_X86_EMU_XXX
> + * symbols.
> + */
> static bool emulation_flags_ok(const struct domain *d, uint32_t emflags)
> {
> + enum {
> + CAP_PV = BIT(0, U),
> + CAP_HVM = BIT(1, U),
> + CAP_HWDOM = BIT(2, U),
> + CAP_DOMU = BIT(3, U),
> + };
> + static const struct {
> + unsigned int caps;
> + uint32_t min;
> + uint32_t opt;
> + } configs[] = {
> +#ifdef CONFIG_PV
> + /* PV */
> + {
> + .caps = CAP_PV | CAP_DOMU,
> + .min = 0,
> + .opt = 0,
Why the latter two initializers? Imo adding ones which say nothing else than
what's the default is only enlarging code without much real benefit.
> + },
> +
> + /* PV dom0 */
> + {
> + .caps = CAP_PV | CAP_HWDOM,
> + .min = X86_EMU_PIT,
> + .opt = 0,
> + },
> +#endif /* #ifdef CONFIG_PV */
> +
> +#ifdef CONFIG_HVM
> + /* PVH dom0 */
> + {
> + .caps = CAP_HVM | CAP_HWDOM,
> + .min = X86_EMU_LAPIC | X86_EMU_IOAPIC | X86_EMU_VPCI,
> + .opt = 0,
> + },
> +
> + /* HVM domU */
> + {
> + .caps = CAP_HVM | CAP_DOMU,
> + .min = X86_EMU_ALL & ~(X86_EMU_VPCI | X86_EMU_USE_PIRQ),
> + /* HVM PIRQ feature is user-selectable. */
> + .opt = X86_EMU_USE_PIRQ,
> + },
> +
> + /* PVH domU */
> + {
> + .caps = CAP_HVM | CAP_DOMU,
> + .min = X86_EMU_LAPIC,
> + .opt = 0,
> + },
> +#endif /* #ifdef CONFIG_HVM */
> + };
> + unsigned int i, caps = is_hardware_domain(d) ? CAP_HWDOM : CAP_DOMU;
> +
> + if ( is_pv_domain(d) )
> + caps |= CAP_PV;
> + else if ( is_hvm_domain(d) )
> + caps |= CAP_HVM;
There's no 3rd case, so this could be expressed with plain "else", and hence
also with a conditional operator, and hence could also be right in the
initializer. How far to go with those transformations I'm not sure; personally
I'd go all the way, but I'd be okay-ish with just the first of the steps.
Jan
