From: Quan Xu Date: Fri, 25 Sep 2015 16:03:04 +0000 (+0200) Subject: vt-d: fix IM bit unmask of Fault Event Control Register in init_vtd_hw() X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~2492 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=26b300bd727ef00a8f60329212a83c3b027a48f7;p=xen.git vt-d: fix IM bit unmask of Fault Event Control Register in init_vtd_hw() Bit 0:29 in Fault Event Control Register are 'Reserved and Preserved', software cannot write 0 to it unconditionally. Software must preserve the value read for writes. Suggested-by: Jan Beulich Signed-off-by: Quan Xu --- diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c index 1d8b561f38..82549376cf 100644 --- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -2012,6 +2012,7 @@ static int init_vtd_hw(void) struct iommu_flush *flush = NULL; int ret; unsigned long flags; + u32 sts; /* * Basic VT-d HW init: set VT-d interrupt, clear VT-d faults. @@ -2025,7 +2026,9 @@ static int init_vtd_hw(void) clear_fault_bits(iommu); spin_lock_irqsave(&iommu->register_lock, flags); - dmar_writel(iommu->reg, DMAR_FECTL_REG, 0); + sts = dmar_readl(iommu->reg, DMAR_FECTL_REG); + sts &= ~DMA_FECTL_IM; + dmar_writel(iommu->reg, DMAR_FECTL_REG, sts); spin_unlock_irqrestore(&iommu->register_lock, flags); }