Peter Maydell <peter.mayd...@linaro.org> writes:
> On Mon, 26 Sept 2022 at 16:08, Alex Bennée <alex.ben...@linaro.org> wrote: >> Peter Maydell <peter.mayd...@linaro.org> writes: >> > On Mon, 26 Sept 2022 at 14:39, Alex Bennée <alex.ben...@linaro.org> wrote: >> >> -static inline int gic_get_current_cpu(GICState *s) >> >> +static inline int gic_get_current_cpu(GICState *s, MemTxAttrs attrs) >> >> { >> >> - if (!qtest_enabled() && s->num_cpu > 1) { >> >> - return current_cpu->cpu_index; >> >> - } >> >> - return 0; >> >> + /* >> >> + * Something other than a CPU accessing the GIC would be a bug as >> >> + * would a CPU index higher than the GICState expects to be >> >> + * handling >> >> + */ >> >> + g_assert(attrs.requester_type == MEMTXATTRS_CPU); >> >> + g_assert(attrs.requester_id < s->num_cpu); >> > >> > Would it be a QEMU bug, or a guest code bug ? If it's possible >> > for the guest to mis-program a DMA controller to do a read that >> > goes through this function, we shouldn't assert. (Whether that >> > can happen will depend on how the board/SoC code puts together >> > the MemoryRegion hierarchy, I think.) >> >> Most likely a QEMU bug - how would a DMA master even access the GIC? > > If it's mapped into the system address space, the same way > as it does any memory access. For instance on the virt board > we just map the distributor MemoryRegion straight into the > system address space, and any DMA master can talk to it. > This is of course not how the hardware really works (where > the GIC is part of the CPU itself), but, as noted in previous > threads, up-ending the MemoryRegion handling in order to be > able to put the GIC only in the address space(s) that the CPU > sees would be a lot of work, which is why we didn't try to > solve the "how do you figure out which CPU is writing to the > GIC" problem that way. So hw_error? I don't think there is a way we can safely continue unless we just want to fallback to "it was vCPU 0 what did it". > > thanks > -- PMM -- Alex Bennée