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Re: [Qemu-devel] [PATCH RFC v3 13/14] intel_iommu: allow dynamic switch

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH RFC v3 13/14] intel_iommu: allow dynamic switch of IOMMU region
Date: Mon, 16 Jan 2017 16:01:00 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1

On 2017年01月16日 15:50, Peter Xu wrote:
On Mon, Jan 16, 2017 at 02:20:31PM +0800, Jason Wang wrote:


diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index fd75112..2596f11 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1343,9 +1343,49 @@ static void vtd_handle_gcmd_sirtp(IntelIOMMUState *s)
      vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_IRTPS);
+static void vtd_switch_address_space(VTDAddressSpace *as, bool iommu_enabled)
Looks like you can check s->dmar_enabled here?
Yes, we need to check old state in case we don't need a switch at all.
Actually I checked it...

I mean is there a chance that iommu_enabled( better name should be dmar_enabled) is not equal to s->dmar_enabled? Looks not.

vtd_handle_gcmd_te() did:

    if (en) {
        s->dmar_enabled = true;
        /* Ok - report back to driver */
        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_TES);
    } else {
        s->dmar_enabled = false;

You can vtd_switch_address_space_all(s, en) after this which will call this function. And another caller like you've pointed out has already call this through s->dmar_enabled. So en here is always s->dmar_enalbed?


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