On 5/20/26 18:38, Duan, Zhenzhong wrote:
Hi
-----Original Message-----
From: Liu, Yi L <[email protected]>
Subject: Re: [PATCH v5 14/15] intel_iommu_accel: Add pasid bits size check
On 5/9/26 12:08, Zhenzhong Duan wrote:
If pasid bits size is bigger than host side, host could fail to emulate
all bindings in guest. Add a check to fail device plug early.
Signed-off-by: Zhenzhong Duan <[email protected]>
Tested-by: Xudong Hao <[email protected]>
Reviewed-by: Clement Mathieu--Drif <[email protected]>
---
hw/i386/intel_iommu_internal.h | 1 +
hw/i386/intel_iommu_accel.c | 8 ++++++++
2 files changed, 9 insertions(+)
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index 2c716c5297..519af3fa90 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -196,6 +196,7 @@
#define VTD_ECAP_SRS (1ULL << 31)
#define VTD_ECAP_NWFS (1ULL << 33)
#define VTD_ECAP_SET_PSS(x, v) ((x)->ecap = deposit64((x)->ecap, 35, 5,
v))
+#define VTD_ECAP_GET_PSS(ecap) extract64(ecap, 35, 5)
#define VTD_ECAP_PASID (1ULL << 40)
#define VTD_ECAP_PDS (1ULL << 42)
#define VTD_ECAP_SMTS (1ULL << 43)
diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
index 4ddf66262c..a0dd6b0ee0 100644
--- a/hw/i386/intel_iommu_accel.c
+++ b/hw/i386/intel_iommu_accel.c
@@ -44,6 +44,7 @@ bool vtd_check_hiod_accel(IntelIOMMUState *s,
VTDHostIOMMUDevice *vtd_hiod,
HostIOMMUDevice *hiod = vtd_hiod->hiod;
struct HostIOMMUDeviceCaps *caps = &hiod->caps;
struct iommu_hw_info_vtd *vtd = &caps->vendor_caps.vtd;
+ uint8_t hpasid = VTD_ECAP_GET_PSS(vtd->ecap_reg) + 1;
PCIBus *bus = vtd_hiod->bus;
PCIDevice *pdev = bus->devices[vtd_hiod->devfn];
@@ -64,6 +65,13 @@ bool vtd_check_hiod_accel(IntelIOMMUState *s,
VTDHostIOMMUDevice *vtd_hiod,
return false;
}
+ /* Only do the check when host device support PASIDs */
+ if (caps->max_pasid_log2 && s->pasid > hpasid) {
the second comparison looks strange. hpasid is derived from ecap_reg,
while ecap_reg is from s->pasid... is there any place that changes
the pss filed of ecap_reg afterward? I think this check should be
against caps->max_pasid_log2 as this is the value from hardware. right?
ecap_reg is from ioctl(IOMMU_GET_HW_INFO), it's not ecap register in vIOMMU.
I see. I misunderstood that the hpasid is got from the vIOMMU ecap
register.
My understanding is that guest kernel will pick the min(caps->max_pasid_log2,
s->pasid), so checking the two doesn't make sense?
I think the caps->max_pasid_log2 should be the same with hpasid since
both are from host. Also, I didn't see the logic to pick the
min(caps->max_pasid_log2, s->pasid). This is not expected just like the
aw bits.
We fail if aw-bits > host aw-bits.
