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Re: [PATCH v2 05/11] hw/intc/gic: use MxTxAttrs to divine accessing CPU
From: |
Alex Bennée |
Subject: |
Re: [PATCH v2 05/11] hw/intc/gic: use MxTxAttrs to divine accessing CPU |
Date: |
Mon, 26 Sep 2022 16:06:34 +0100 |
User-agent: |
mu4e 1.9.0; emacs 28.2.50 |
Peter Maydell <peter.maydell@linaro.org> writes:
> On Mon, 26 Sept 2022 at 14:39, Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>> Now that MxTxAttrs encodes a CPU we should use that to figure it out.
>> This solves edge cases like accessing via gdbstub or qtest.
>>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/124
>>
>> ---
>> v2
>> - update for new field
>> - bool asserts
>> ---
>> hw/intc/arm_gic.c | 39 ++++++++++++++++++++++-----------------
>> 1 file changed, 22 insertions(+), 17 deletions(-)
>>
>> diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c
>> index 492b2421ab..d907df3884 100644
>> --- a/hw/intc/arm_gic.c
>> +++ b/hw/intc/arm_gic.c
>> @@ -56,17 +56,22 @@ static const uint8_t gic_id_gicv2[] = {
>> 0x04, 0x00, 0x00, 0x00, 0x90, 0xb4, 0x2b, 0x00, 0x0d, 0xf0, 0x05, 0xb1
>> };
>>
>> -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?
>
> thanks
> -- PMM
--
Alex Bennée
- Re: [PATCH v2 01/11] hw: encode accessing CPU index in MemTxAttrs, (continued)
- [PATCH v2 03/11] target/arm: ensure HVF traps set appropriate MemTxAttrs, Alex Bennée, 2022/09/26
- [PATCH v2 08/11] gdbstub: move into its own sub directory, Alex Bennée, 2022/09/26
- [PATCH v2 06/11] hw/timer: convert mptimer access to attrs to derive cpu index, Alex Bennée, 2022/09/26
- [PATCH v2 09/11] gdbstub: move sstep flags probing into AccelClass, Alex Bennée, 2022/09/26
- [PATCH v2 10/11] gdbstub: move breakpoint logic to accel ops, Alex Bennée, 2022/09/26
- [PATCH v2 05/11] hw/intc/gic: use MxTxAttrs to divine accessing CPU, Alex Bennée, 2022/09/26
[PATCH v2 11/11] gdbstub: move guest debug support check to ops, Alex Bennée, 2022/09/26