[v2] support unaligned access to xHCI Capability

[RFC PATCH v2 7/9] system/memory: assert on invalid unaligned combo

CJ Chen posted 9 patches 2 months, 3 weeks ago

Diff against v1 v2
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Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>, Jesper Devantier <foss@defmacro.it>, Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>, Tyrone Ting <kfting@nuvoton.com>, Hao Wu <wuhaotsh@google.com>, Max Filippov <jcmvbkbc@gmail.com>, Peter Xu <peterx@redhat.com>, David Hildenbrand <david@redhat.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Fabiano Rosas <farosas@suse.de>, Laurent Vivier <lvivier@redhat.com>

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[RFC PATCH v2 7/9] system/memory: assert on invalid unaligned combo

Posted by CJ Chen 2 months, 3 weeks ago

When it comes to this pattern: .valid.unaligned = false and
impl.unaligned = true, is effectlvely contradictory. The .valid
structure indicates that unaligned access should be rejected at
the access validation phase, yet .impl suggests the underlying
device implementation can handle unaligned operations. As a result,
the upper-layer code will never even reach the .impl logic, leading
to confusion.

Signed-off-by: CJ Chen <cjchen@igel.co.jp>
Tested-by: CJ Chen <cjchen@igel.co.jp>
Suggested-by: Peter Xu <peterx@redhat.com>
Acked-by: Tomoyuki Hirose <hrstmyk811m@gmail.com>
---
 system/memory.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/system/memory.c b/system/memory.c
index d6071b4414..b536a62ce9 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -1654,6 +1654,7 @@ void memory_region_init_io(MemoryRegion *mr,
                            const char *name,
                            uint64_t size)
 {
+    g_assert(!ops || !(ops->impl.unaligned && !ops->valid.unaligned));
     memory_region_init(mr, owner, name, size);
     mr->ops = ops ? ops : &unassigned_mem_ops;
     mr->opaque = opaque;
-- 
2.25.1

Re: [RFC PATCH v2 7/9] system/memory: assert on invalid unaligned combo

Posted by Philippe Mathieu-Daudé 2 months, 3 weeks ago

On 22/8/25 11:24, CJ Chen wrote:
> When it comes to this pattern: .valid.unaligned = false and
> impl.unaligned = true, is effectlvely contradictory. The .valid
> structure indicates that unaligned access should be rejected at
> the access validation phase, yet .impl suggests the underlying
> device implementation can handle unaligned operations. As a result,
> the upper-layer code will never even reach the .impl logic, leading
> to confusion.
> 
> Signed-off-by: CJ Chen <cjchen@igel.co.jp>
> Tested-by: CJ Chen <cjchen@igel.co.jp>

It is normal for contributors to test their patches ;)

> Suggested-by: Peter Xu <peterx@redhat.com>
> Acked-by: Tomoyuki Hirose <hrstmyk811m@gmail.com>
> ---
>   system/memory.c | 1 +
>   1 file changed, 1 insertion(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>