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Re: [Qemu-devel] [PATCH] intel-iommu: Accept 64-bit writes to FEADDR
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH] intel-iommu: Accept 64-bit writes to FEADDR |
Date: |
Thu, 22 Feb 2018 12:40:13 +0800 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Sat, Feb 17, 2018 at 12:26:19PM +0100, Jan Kiszka wrote:
> From: Jan Kiszka <address@hidden>
>
> Xen is doing this [1] and currently triggers an abort.
>
> [1]
> http://xenbits.xenproject.org/gitweb/?p=xen.git;a=blob;f=xen/drivers/passthrough/vtd/iommu.c;h=daaed0abbdd06b6ba3d948ea103aadf02651e83c;hb=refs/heads/master#l1108
>
> Reported-by: Luis Lloret <address@hidden>
> Signed-off-by: Jan Kiszka <address@hidden>
> ---
> hw/i386/intel_iommu.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 2e841cde27..b61d0da270 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -2129,7 +2129,12 @@ static void vtd_mem_write(void *opaque, hwaddr addr,
>
> /* Fault Event Address Register, 32-bit */
> case DMAR_FEADDR_REG:
> - assert(size == 4);
> + /*
> + * While the register is 32-bit only, some guests (Xen...) write to
> it
> + * with 64-bit. Ignore the upper part, that's likely what the
> hardware
> + * does as well (plus the upper part is not used by our model
> anyway).
> + */
> + assert(size >= 4);
> vtd_set_long(s, addr, val);
> break;
(Sorry for the late response due to Chinese Spring Festival)
I agree with the problem there, but do we still better provide a
conditional vtd_set_quad()? Since from the spec 10.4.13 the upper 32
bits may still be used when x2apic (Extended Interrupt Mode) is
enabled?
Thanks,
--
Peter Xu