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Re: [Qemu-devel] MSI interrupt support with vioscsi.c miniport driver
From: |
Yan Vugenfirer |
Subject: |
Re: [Qemu-devel] MSI interrupt support with vioscsi.c miniport driver |
Date: |
Sun, 9 Feb 2014 11:24:07 +0200 |
Hi Nicholas,
Adding Vadim Rozenfeld who wrote the virtio-scsi driver.
Best regards,
Yan.
On Feb 7, 2014, at 10:14 PM, Nicholas A. Bellinger <address@hidden> wrote:
> Hi Yan,
>
> So recently I've been doing some KVM guest performance comparisons
> between the scsi-mq prototype using virtio-scsi + vhost-scsi, and
> Windows Server 2012 with vioscsi.sys (virtio-win-0.1-74.iso) +
> vhost-scsi using PCIe flash backend devices.
>
> I've noticed that small block random performance for the MSFT guest is
> at around ~80K IOPs with multiple vioscsi LUNs + adapters, which ends up
> being well below what the Linux guest with scsi-mq + virtio-scsi is
> capable of (~500K).
>
> After searching through the various vioscsi registry settings, it
> appears that MSIEnabled is being explicitly disabled (0x00000000), that
> is different from what vioscsi.inx is currently defining:
>
> [pnpsafe_pci_addreg_msix]
> HKR, "Interrupt Management",, 0x00000010
> HKR, "Interrupt Management\MessageSignaledInterruptProperties",, 0x00000010
> HKR, "Interrupt Management\MessageSignaledInterruptProperties", MSISupported,
> 0x00010001, 0
> HKR, "Interrupt Management\MessageSignaledInterruptProperties",
> MessageNumberLimit, 0x00010001, 4
>
> Looking deeper at vioscsi.c code, I've noticed that MSI_SUPPORTED=0 is
> explicitly disabled at build time in SOURCES + vioscsi.vcxproj, as well
> as VioScsiFindAdapter() code always ends setting msix_enabled = FALSE
> here, regardless of MSI_SUPPORTED:
>
>
> https://github.com/YanVugenfirer/kvm-guest-drivers-windows/blob/master/vioscsi/vioscsi.c#L340
>
> Also looking at virtio_stor.c for the raw block driver, MSI_SUPPORTED=1
> appears to be the default setting for the driver included in the offical
> virtio-win iso builds, right..?
>
> Sooo, I'd like to try enabling MSI_SUPPORTED=1 in a test vioscsi.sys
> build of my own, but before going down the WDK development rabbit whole,
> I'd like to better understand why you've explicitly disabled this logic
> within vioscsi.c code to start..?
>
> Is there anything that needs to be addressed / carried over from
> virtio_stor.c in order to get MSI_SUPPORTED=1 to work with vioscsi.c
> miniport code..?
>
> TIA!
>
> --nab
>
>