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Re: [Qemu-devel] [PATCH v2] msix: don't mask already masked vectors on r
From: |
Marcel Apfelbaum |
Subject: |
Re: [Qemu-devel] [PATCH v2] msix: don't mask already masked vectors on reset |
Date: |
Fri, 8 Dec 2017 09:09:06 -0500 (EST) |
----- Original Message -----
> From: "Ladi Prosek" <address@hidden>
> To: address@hidden
> Cc: address@hidden, address@hidden, address@hidden, "alex williamson"
> <address@hidden>
> Sent: Friday, December 8, 2017 8:31:13 AM
> Subject: [PATCH v2] msix: don't mask already masked vectors on reset
>
> msix_mask_all() is supposed to invoke the release vector notifier if the
> state of the
> respective vector changed from unmasked to masked. The way it's currently
> called from
> msix_reset(), though, may result in calling the release notifier even if the
> vector
> is already masked.
>
> 1) msix_reset() clears out the msix_cap field and the msix_table.
> 2) msix_mask_all() runs with was_masked=false for all vectors because of 1),
> which
> results in calling the release notifier on all vectors.
> 3) if msix_reset() is subsequently called again, it goes through the same
> steps and
> calls the release notifier on all vectors again.
>
> This commit moves msix_mask_all() up so it runs before the device state is
> lost. And
> it adds an assignment to msix_function_masked so that the device remembers
> that
> MSI-X is masked.
>
> This is likely a low impact issue, found while debugging an already broken
> device. It
> is however easy to fix and the expectation that the use and release notifier
> invocations
> are always balanced is very natural.
>
> Signed-off-by: Ladi Prosek <address@hidden>
> ---
>
> v1->v2:
> * fixed typo in commit message "or" -> "to" (Marcel)
> * directly set msix_function_masked to true instead of calling
> msix_update_function_masked() (Marcel)
>
>
> hw/pci/msix.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/pci/msix.c b/hw/pci/msix.c
> index c944c02135..d6a4dbdb6b 100644
> --- a/hw/pci/msix.c
> +++ b/hw/pci/msix.c
> @@ -500,11 +500,12 @@ void msix_reset(PCIDevice *dev)
> return;
> }
> msix_clear_all_vectors(dev);
> + msix_mask_all(dev, dev->msix_entries_nr);
> dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] &=
> ~dev->wmask[dev->msix_cap + MSIX_CONTROL_OFFSET];
> memset(dev->msix_table, 0, dev->msix_entries_nr * PCI_MSIX_ENTRY_SIZE);
> memset(dev->msix_pba, 0, QEMU_ALIGN_UP(dev->msix_entries_nr, 64) / 8);
> - msix_mask_all(dev, dev->msix_entries_nr);
> + dev->msix_function_masked = true;
> }
>
> /* PCI spec suggests that devices make it possible for software to configure
> --
> 2.13.6
>
>
Thanks Ladi!
Reviewed-by: Marcel Apfelbaum <address@hidden>