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Re: [PATCH V4 14/24] arm/ioreq: Introduce arch specific bits for IOREQ/DM features

On 17/01/2021 17:11, Oleksandr wrote:

On 15.01.21 22:26, Julien Grall wrote:

Hi Julien

Hi Oleksandr,

          ret = relinquish_memory(d, &d->xenpage_list);
          if ( ret )
diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index ae7ef96..9814481 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -16,6 +16,7 @@
   * GNU General Public License for more details.
  +#include <xen/ioreq.h>
  #include <xen/lib.h>
  #include <xen/spinlock.h>
  #include <xen/sched.h>
@@ -23,6 +24,7 @@
  #include <asm/cpuerrata.h>
  #include <asm/current.h>
  #include <asm/mmio.h>
+#include <asm/hvm/ioreq.h>

Shouldn't this have been included by "xen/ioreq.h"?
Well, for V1 asm/hvm/ioreq.h was included by xen/ioreq.h. But, it turned out that there was nothing inside common header required arch one to be included and I was asked to include arch header where it was indeed needed (several *.c files).

Fair enough.


If you return IO_HANDLED here, then it means the we will take care of previous I/O but the current one is going to be ignored.
Which current one? As I understand, if try_fwd_ioserv() gets called with vio->req.state == STATE_IORESP_READY then this is a second round after emulator completes the emulation (the first round was when we returned IO_RETRY down the function and claimed that we would need a completion), so we are still dealing with previous I/O. vcpu_ioreq_handle_completion() -> arch_ioreq_complete_mmio() -> try_handle_mmio() -> try_fwd_ioserv() -> handle_ioserv() And after we return IO_HANDLED here, handle_ioserv() will be called to complete the handling of this previous I/O emulation.
Or I really missed something?

Hmmm... I somehow thought try_fw_ioserv() would only be called the first time. Do you have a branch with your code applied? This would help to follow the different paths.

  diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 6819a3b..c235e5b 100644
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -10,6 +10,7 @@
  #include <asm/gic.h>
  #include <asm/vgic.h>
  #include <asm/vpl011.h>
+#include <public/hvm/dm_op.h>

May I ask, why do you need to include dm_op.h here?
I needed to include that header to make some bits visible (XEN_DMOP_IO_RANGE_PCI, struct xen_dm_op_buf, etc). Why here - is a really good question. I don't remember exactly, probably I followed x86's domain.h which also included it. So, trying to remove the inclusion here, I get several build failures on Arm which could be fixed if I include that header from dm.h and ioreq.h:

Shall I do this way?

If the failure are indeded because ioreq.h and dm.h use definition from public/hvm/dm_op.h, then yes. Can you post the errors?


  #include <public/hvm/params.h>
    struct hvm_domain
@@ -262,6 +263,8 @@ static inline void arch_vcpu_block(struct vcpu *v) {}     #define arch_vm_assist_valid_mask(d) (1UL << VMASST_TYPE_runstate_update_flag)
  +#define has_vpci(d)    ({ (void)(d); false; })
  #endif /* __ASM_DOMAIN_H__ */
diff --git a/xen/include/asm-arm/hvm/ioreq.h b/xen/include/asm-arm/hvm/ioreq.h
new file mode 100644
index 0000000..19e1247
--- /dev/null
+++ b/xen/include/asm-arm/hvm/ioreq.h

Shouldn't this directly be under asm-arm/ rather than asm-arm/hvm/ as the IOREQ is now meant to be agnostic?
Good question... The _common_ IOREQ code is indeed arch-agnostic. But, can the _arch_ IOREQ code be treated as really subarch-agnostic? I think, on Arm it can and it is most likely ok to keep it in "asm-arm/", but how it would be correlated with x86's IOREQ code which is HVM specific and located
in "hvm" subdir?

Sorry, I don't understand your answer/questions. So let me ask the question differently, is asm-arm/hvm/ioreq.h going to be included from common code?

If the answer is no, then I see no reason to follow the x86 here.
If the answer is yes, then I am quite confused why half of the series tried to remove "hvm" from the function name but we still include "asm/hvm/ioreq.h".


Julien Grall



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