When guest deletes PASID entries, QEMU will capture the pasid cache
invalidation request, walk through pasid_cache_list in each passthrough
device to find stale VTDACCELPASIDCacheEntry and delete them.
This happen before the PASID entry addition, because a new added entry
should never be removed.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
---
hw/i386/intel_iommu_accel.c | 70 +++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
index 0acf3ae77f..5a956af916 100644
--- a/hw/i386/intel_iommu_accel.c
+++ b/hw/i386/intel_iommu_accel.c
@@ -16,6 +16,28 @@
#include "hw/pci/pci_bus.h"
#include "trace.h"
+static inline int vtd_hiod_get_pe_from_pasid(VTDACCELPASIDCacheEntry *vtd_pce,
+ VTDPASIDEntry *pe)
+{
+ VTDHostIOMMUDevice *vtd_hiod = vtd_pce->vtd_hiod;
+ IntelIOMMUState *s = vtd_hiod->iommu_state;
+ uint32_t pasid = vtd_pce->pasid;
+ VTDContextEntry ce;
+ int ret;
+
+ if (!s->dmar_enabled || !s->root_scalable) {
+ return -VTD_FR_RTADDR_INV_TTM;
+ }
+
+ ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_hiod->bus),
+ vtd_hiod->devfn, &ce);
+ if (ret) {
+ return ret;
+ }
+
+ return vtd_ce_get_pasid_entry(s, &ce, pe, pasid);
+}
+
bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice *vtd_hiod,
Error **errp)
{
@@ -257,6 +279,52 @@ void vtd_flush_host_piotlb_all_locked(IntelIOMMUState *s, uint16_t domain_id,
vtd_flush_host_piotlb_locked, &piotlb_info);
}
+static void vtd_pasid_cache_invalidate_one(VTDACCELPASIDCacheEntry *vtd_pce,
+ VTDPASIDCacheInfo *pc_info)
+{
+ VTDPASIDEntry pe;
+ uint16_t did;
+
+ /*
+ * VTD_INV_DESC_PASIDC_G_DSI and VTD_INV_DESC_PASIDC_G_PASID_SI require
+ * DID check. If DID doesn't match the value in cache or memory, then
+ * it's not a pasid entry we want to invalidate.
+ */
+ switch (pc_info->type) {
+ case VTD_INV_DESC_PASIDC_G_PASID_SI:
+ if (pc_info->pasid != vtd_pce->pasid) {
+ return;
+ }
+ /* Fall through */
+ case VTD_INV_DESC_PASIDC_G_DSI:
+ did = VTD_SM_PASID_ENTRY_DID(&vtd_pce->pe);
+ if (pc_info->did != did) {
+ return;
+ }
+ }
+
+ if (vtd_hiod_get_pe_from_pasid(vtd_pce, &pe)) {
+ /*
+ * No valid pasid entry in guest memory. e.g. pasid entry was modified
+ * to be either all-zero or non-present. Either case means existing
+ * pasid cache should be invalidated.
+ */
+ QLIST_REMOVE(vtd_pce, next);
+ g_free(vtd_pce);
+ }
+}
+
+/* Delete invalid pasid cache entry from pasid_cache_list */
+static void vtd_pasid_cache_invalidate(VTDHostIOMMUDevice *vtd_hiod,
+ VTDPASIDCacheInfo *pc_info)
+{
+ VTDACCELPASIDCacheEntry *vtd_pce, *next;
+
+ QLIST_FOREACH_SAFE(vtd_pce, &vtd_hiod->pasid_cache_list, next, next) {
+ vtd_pasid_cache_invalidate_one(vtd_pce, pc_info);
+ }
+}
+
static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t pasid,
VTDPASIDEntry *pe)
{
@@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState *s, VTDPASIDCacheInfo *pc_info)
TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
continue;
}
+
+ vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
}
}
--
2.47.3On 3/6/26 11:44, Zhenzhong Duan wrote:
> When guest deletes PASID entries, QEMU will capture the pasid cache
> invalidation request, walk through pasid_cache_list in each passthrough
> device to find stale VTDACCELPASIDCacheEntry and delete them.
As the comment to the last patch, I think this patch should handle both
update and removal of PASID entry.
> This happen before the PASID entry addition, because a new added entry
> should never be removed.
This is confusing. TBH. this order is not quite important as the current
implementation, we don't have multiple pasid entires share same cache
entry, so a given pasid entry, we either add new cache entry or
update/delete cache entry. So I would just drop this line.
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
> hw/i386/intel_iommu_accel.c | 70 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 70 insertions(+)
>
> diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
> index 0acf3ae77f..5a956af916 100644
> --- a/hw/i386/intel_iommu_accel.c
> +++ b/hw/i386/intel_iommu_accel.c
> @@ -16,6 +16,28 @@
> #include "hw/pci/pci_bus.h"
> #include "trace.h"
>
> +static inline int vtd_hiod_get_pe_from_pasid(VTDACCELPASIDCacheEntry *vtd_pce,
> + VTDPASIDEntry *pe)
> +{
> + VTDHostIOMMUDevice *vtd_hiod = vtd_pce->vtd_hiod;
> + IntelIOMMUState *s = vtd_hiod->iommu_state;
> + uint32_t pasid = vtd_pce->pasid;
> + VTDContextEntry ce;
> + int ret;
> +
> + if (!s->dmar_enabled || !s->root_scalable) {
> + return -VTD_FR_RTADDR_INV_TTM;
> + }
> +
> + ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_hiod->bus),
> + vtd_hiod->devfn, &ce);
> + if (ret) {
> + return ret;
> + }
> +
> + return vtd_ce_get_pasid_entry(s, &ce, pe, pasid);
> +}
> +
> bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice *vtd_hiod,
> Error **errp)
> {
> @@ -257,6 +279,52 @@ void vtd_flush_host_piotlb_all_locked(IntelIOMMUState *s, uint16_t domain_id,
> vtd_flush_host_piotlb_locked, &piotlb_info);
> }
>
> +static void vtd_pasid_cache_invalidate_one(VTDACCELPASIDCacheEntry *vtd_pce,
> + VTDPASIDCacheInfo *pc_info)
> +{
> + VTDPASIDEntry pe;
> + uint16_t did;
> +
> + /*
> + * VTD_INV_DESC_PASIDC_G_DSI and VTD_INV_DESC_PASIDC_G_PASID_SI require
> + * DID check. If DID doesn't match the value in cache or memory, then
> + * it's not a pasid entry we want to invalidate.
> + */
> + switch (pc_info->type) {
> + case VTD_INV_DESC_PASIDC_G_PASID_SI:
> + if (pc_info->pasid != vtd_pce->pasid) {
> + return;
> + }
> + /* Fall through */
> + case VTD_INV_DESC_PASIDC_G_DSI:
> + did = VTD_SM_PASID_ENTRY_DID(&vtd_pce->pe);
> + if (pc_info->did != did) {
> + return;
> + }
> + }
> +
> + if (vtd_hiod_get_pe_from_pasid(vtd_pce, &pe)) {
> + /*
> + * No valid pasid entry in guest memory. e.g. pasid entry was modified
> + * to be either all-zero or non-present. Either case means existing
> + * pasid cache should be invalidated.
> + */
> + QLIST_REMOVE(vtd_pce, next);
> + g_free(vtd_pce);
call vtd_accel_update_pc() and vtd_accel_delete_pc() accordingly.
> + }
> +}
> +
> +/* Delete invalid pasid cache entry from pasid_cache_list */
> +static void vtd_pasid_cache_invalidate(VTDHostIOMMUDevice *vtd_hiod,
> + VTDPASIDCacheInfo *pc_info)
> +{
> + VTDACCELPASIDCacheEntry *vtd_pce, *next;
> +
> + QLIST_FOREACH_SAFE(vtd_pce, &vtd_hiod->pasid_cache_list, next, next) {
> + vtd_pasid_cache_invalidate_one(vtd_pce, pc_info);
> + }
> +}
> +
> static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t pasid,
> VTDPASIDEntry *pe)
> {
> @@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState *s, VTDPASIDCacheInfo *pc_info)
> TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
> continue;
> }
> +
> + vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
> vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
> }
> }
>-----Original Message-----
>From: Liu, Yi L <yi.l.liu@intel.com>
>Subject: Re: [PATCH v1 08/13] intel_iommu: Handle PASID entry removal for
>pc_inv_dsc request
>
>On 3/6/26 11:44, Zhenzhong Duan wrote:
>> When guest deletes PASID entries, QEMU will capture the pasid cache
>> invalidation request, walk through pasid_cache_list in each passthrough
>> device to find stale VTDACCELPASIDCacheEntry and delete them.
>
>As the comment to the last patch, I think this patch should handle both
>update and removal of PASID entry.
>
>> This happen before the PASID entry addition, because a new added entry
>> should never be removed.
>
>This is confusing. TBH. this order is not quite important as the current
>implementation, we don't have multiple pasid entires share same cache
>entry, so a given pasid entry, we either add new cache entry or
>update/delete cache entry. So I would just drop this line.
OK, will remove it.
In fact, the order is for performance reason. Imaging there are lots of pasid entires
in pasid_cache_list, we remove stale entries first, then in addition code when we
loop on pasid_cache_list to see if a new pasid entry already exists, we can iterate
less entries.
Thanks
Zhenzhong
>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>> hw/i386/intel_iommu_accel.c | 70
>+++++++++++++++++++++++++++++++++++++
>> 1 file changed, 70 insertions(+)
>>
>> diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
>> index 0acf3ae77f..5a956af916 100644
>> --- a/hw/i386/intel_iommu_accel.c
>> +++ b/hw/i386/intel_iommu_accel.c
>> @@ -16,6 +16,28 @@
>> #include "hw/pci/pci_bus.h"
>> #include "trace.h"
>>
>> +static inline int vtd_hiod_get_pe_from_pasid(VTDACCELPASIDCacheEntry
>*vtd_pce,
>> + VTDPASIDEntry *pe)
>> +{
>> + VTDHostIOMMUDevice *vtd_hiod = vtd_pce->vtd_hiod;
>> + IntelIOMMUState *s = vtd_hiod->iommu_state;
>> + uint32_t pasid = vtd_pce->pasid;
>> + VTDContextEntry ce;
>> + int ret;
>> +
>> + if (!s->dmar_enabled || !s->root_scalable) {
>> + return -VTD_FR_RTADDR_INV_TTM;
>> + }
>> +
>> + ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_hiod->bus),
>> + vtd_hiod->devfn, &ce);
>> + if (ret) {
>> + return ret;
>> + }
>> +
>> + return vtd_ce_get_pasid_entry(s, &ce, pe, pasid);
>> +}
>> +
>> bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice
>*vtd_hiod,
>> Error **errp)
>> {
>> @@ -257,6 +279,52 @@ void
>vtd_flush_host_piotlb_all_locked(IntelIOMMUState *s, uint16_t domain_id,
>> vtd_flush_host_piotlb_locked, &piotlb_info);
>> }
>>
>> +static void vtd_pasid_cache_invalidate_one(VTDACCELPASIDCacheEntry
>*vtd_pce,
>> + VTDPASIDCacheInfo *pc_info)
>> +{
>> + VTDPASIDEntry pe;
>> + uint16_t did;
>> +
>> + /*
>> + * VTD_INV_DESC_PASIDC_G_DSI and VTD_INV_DESC_PASIDC_G_PASID_SI
>require
>> + * DID check. If DID doesn't match the value in cache or memory, then
>> + * it's not a pasid entry we want to invalidate.
>> + */
>> + switch (pc_info->type) {
>> + case VTD_INV_DESC_PASIDC_G_PASID_SI:
>> + if (pc_info->pasid != vtd_pce->pasid) {
>> + return;
>> + }
>> + /* Fall through */
>> + case VTD_INV_DESC_PASIDC_G_DSI:
>> + did = VTD_SM_PASID_ENTRY_DID(&vtd_pce->pe);
>> + if (pc_info->did != did) {
>> + return;
>> + }
>> + }
>> +
>> + if (vtd_hiod_get_pe_from_pasid(vtd_pce, &pe)) {
>> + /*
>> + * No valid pasid entry in guest memory. e.g. pasid entry was modified
>> + * to be either all-zero or non-present. Either case means existing
>> + * pasid cache should be invalidated.
>> + */
>> + QLIST_REMOVE(vtd_pce, next);
>> + g_free(vtd_pce);
>
>call vtd_accel_update_pc() and vtd_accel_delete_pc() accordingly.
>
>> + }
>> +}
>> +
>> +/* Delete invalid pasid cache entry from pasid_cache_list */
>> +static void vtd_pasid_cache_invalidate(VTDHostIOMMUDevice *vtd_hiod,
>> + VTDPASIDCacheInfo *pc_info)
>> +{
>> + VTDACCELPASIDCacheEntry *vtd_pce, *next;
>> +
>> + QLIST_FOREACH_SAFE(vtd_pce, &vtd_hiod->pasid_cache_list, next, next) {
>> + vtd_pasid_cache_invalidate_one(vtd_pce, pc_info);
>> + }
>> +}
>> +
>> static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t pasid,
>> VTDPASIDEntry *pe)
>> {
>> @@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState *s,
>VTDPASIDCacheInfo *pc_info)
>> TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
>> continue;
>> }
>> +
>> + vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
>> vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
>> }
>> }
On 3/23/26 14:08, Duan, Zhenzhong wrote:
>>> static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t pasid,
>>> VTDPASIDEntry *pe)
>>> {
>>> @@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState *s,
>> VTDPASIDCacheInfo *pc_info)
>>> TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
>>> continue;
>>> }
>>> +
>>> + vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
>>> vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
a minor optimization, for PASDI selective, if
vtd_pasid_cache_invalidate() already handled the invalidation, then the
vtd_replay_pasid_bind_for_dev() can be skipped.
>-----Original Message-----
>From: Liu, Yi L <yi.l.liu@intel.com>
>Subject: Re: [PATCH v1 08/13] intel_iommu: Handle PASID entry removal for
>pc_inv_dsc request
>
>On 3/23/26 14:08, Duan, Zhenzhong wrote:
>
>>>> static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t
>pasid,
>>>> VTDPASIDEntry *pe)
>>>> {
>>>> @@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState
>*s,
>>> VTDPASIDCacheInfo *pc_info)
>>>> TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
>>>> continue;
>>>> }
>>>> +
>>>> + vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
>>>> vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
>
>a minor optimization, for PASDI selective, if
>vtd_pasid_cache_invalidate() already handled the invalidation, then the
>vtd_replay_pasid_bind_for_dev() can be skipped.
Good idea, will do.
Thanks
Zhenzhong
On 3/23/26 14:08, Duan, Zhenzhong wrote:
>
>
>> -----Original Message-----
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Subject: Re: [PATCH v1 08/13] intel_iommu: Handle PASID entry removal for
>> pc_inv_dsc request
>>
>> On 3/6/26 11:44, Zhenzhong Duan wrote:
>>> When guest deletes PASID entries, QEMU will capture the pasid cache
>>> invalidation request, walk through pasid_cache_list in each passthrough
>>> device to find stale VTDACCELPASIDCacheEntry and delete them.
>>
>> As the comment to the last patch, I think this patch should handle both
>> update and removal of PASID entry.
>>
>>> This happen before the PASID entry addition, because a new added entry
>>> should never be removed.
>>
>> This is confusing. TBH. this order is not quite important as the current
>> implementation, we don't have multiple pasid entires share same cache
>> entry, so a given pasid entry, we either add new cache entry or
>> update/delete cache entry. So I would just drop this line.
>
> OK, will remove it.
>
> In fact, the order is for performance reason. Imaging there are lots of pasid entires
> in pasid_cache_list, we remove stale entries first, then in addition code when we
> loop on pasid_cache_list to see if a new pasid entry already exists, we can iterate
> less entries.
got it. you can mark it in the code.
> Thanks
> Zhenzhong
>
>>
>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>> ---
>>> hw/i386/intel_iommu_accel.c | 70
>> +++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 70 insertions(+)
>>>
>>> diff --git a/hw/i386/intel_iommu_accel.c b/hw/i386/intel_iommu_accel.c
>>> index 0acf3ae77f..5a956af916 100644
>>> --- a/hw/i386/intel_iommu_accel.c
>>> +++ b/hw/i386/intel_iommu_accel.c
>>> @@ -16,6 +16,28 @@
>>> #include "hw/pci/pci_bus.h"
>>> #include "trace.h"
>>>
>>> +static inline int vtd_hiod_get_pe_from_pasid(VTDACCELPASIDCacheEntry
>> *vtd_pce,
>>> + VTDPASIDEntry *pe)
>>> +{
>>> + VTDHostIOMMUDevice *vtd_hiod = vtd_pce->vtd_hiod;
>>> + IntelIOMMUState *s = vtd_hiod->iommu_state;
>>> + uint32_t pasid = vtd_pce->pasid;
>>> + VTDContextEntry ce;
>>> + int ret;
>>> +
>>> + if (!s->dmar_enabled || !s->root_scalable) {
>>> + return -VTD_FR_RTADDR_INV_TTM;
>>> + }
>>> +
>>> + ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_hiod->bus),
>>> + vtd_hiod->devfn, &ce);
>>> + if (ret) {
>>> + return ret;
>>> + }
>>> +
>>> + return vtd_ce_get_pasid_entry(s, &ce, pe, pasid);
>>> +}
>>> +
>>> bool vtd_check_hiod_accel(IntelIOMMUState *s, VTDHostIOMMUDevice
>> *vtd_hiod,
>>> Error **errp)
>>> {
>>> @@ -257,6 +279,52 @@ void
>> vtd_flush_host_piotlb_all_locked(IntelIOMMUState *s, uint16_t domain_id,
>>> vtd_flush_host_piotlb_locked, &piotlb_info);
>>> }
>>>
>>> +static void vtd_pasid_cache_invalidate_one(VTDACCELPASIDCacheEntry
>> *vtd_pce,
>>> + VTDPASIDCacheInfo *pc_info)
>>> +{
>>> + VTDPASIDEntry pe;
>>> + uint16_t did;
>>> +
>>> + /*
>>> + * VTD_INV_DESC_PASIDC_G_DSI and VTD_INV_DESC_PASIDC_G_PASID_SI
>> require
>>> + * DID check. If DID doesn't match the value in cache or memory, then
>>> + * it's not a pasid entry we want to invalidate.
>>> + */
>>> + switch (pc_info->type) {
>>> + case VTD_INV_DESC_PASIDC_G_PASID_SI:
>>> + if (pc_info->pasid != vtd_pce->pasid) {
>>> + return;
>>> + }
>>> + /* Fall through */
>>> + case VTD_INV_DESC_PASIDC_G_DSI:
>>> + did = VTD_SM_PASID_ENTRY_DID(&vtd_pce->pe);
>>> + if (pc_info->did != did) {
>>> + return;
>>> + }
>>> + }
>>> +
>>> + if (vtd_hiod_get_pe_from_pasid(vtd_pce, &pe)) {
>>> + /*
>>> + * No valid pasid entry in guest memory. e.g. pasid entry was modified
>>> + * to be either all-zero or non-present. Either case means existing
>>> + * pasid cache should be invalidated.
>>> + */
>>> + QLIST_REMOVE(vtd_pce, next);
>>> + g_free(vtd_pce);
>>
>> call vtd_accel_update_pc() and vtd_accel_delete_pc() accordingly.
>>
>>> + }
>>> +}
>>> +
>>> +/* Delete invalid pasid cache entry from pasid_cache_list */
>>> +static void vtd_pasid_cache_invalidate(VTDHostIOMMUDevice *vtd_hiod,
>>> + VTDPASIDCacheInfo *pc_info)
>>> +{
>>> + VTDACCELPASIDCacheEntry *vtd_pce, *next;
>>> +
>>> + QLIST_FOREACH_SAFE(vtd_pce, &vtd_hiod->pasid_cache_list, next, next) {
>>> + vtd_pasid_cache_invalidate_one(vtd_pce, pc_info);
>>> + }
>>> +}
>>> +
>>> static void vtd_find_add_pc(VTDHostIOMMUDevice *vtd_hiod, uint32_t pasid,
>>> VTDPASIDEntry *pe)
>>> {
>>> @@ -423,6 +491,8 @@ void vtd_pasid_cache_sync_accel(IntelIOMMUState *s,
>> VTDPASIDCacheInfo *pc_info)
>>> TYPE_HOST_IOMMU_DEVICE_IOMMUFD)) {
>>> continue;
>>> }
>>> +
>>> + vtd_pasid_cache_invalidate(vtd_hiod, pc_info);
>>> vtd_replay_pasid_bind_for_dev(vtd_hiod, start, end, pc_info);
>>> }
>>> }
>
>-----Original Message----- >From: Liu, Yi L <yi.l.liu@intel.com> >Subject: Re: [PATCH v1 08/13] intel_iommu: Handle PASID entry removal for >pc_inv_dsc request > >On 3/23/26 14:08, Duan, Zhenzhong wrote: >> >> >>> -----Original Message----- >>> From: Liu, Yi L <yi.l.liu@intel.com> >>> Subject: Re: [PATCH v1 08/13] intel_iommu: Handle PASID entry removal for >>> pc_inv_dsc request >>> >>> On 3/6/26 11:44, Zhenzhong Duan wrote: >>>> When guest deletes PASID entries, QEMU will capture the pasid cache >>>> invalidation request, walk through pasid_cache_list in each passthrough >>>> device to find stale VTDACCELPASIDCacheEntry and delete them. >>> >>> As the comment to the last patch, I think this patch should handle both >>> update and removal of PASID entry. >>> >>>> This happen before the PASID entry addition, because a new added entry >>>> should never be removed. >>> >>> This is confusing. TBH. this order is not quite important as the current >>> implementation, we don't have multiple pasid entires share same cache >>> entry, so a given pasid entry, we either add new cache entry or >>> update/delete cache entry. So I would just drop this line. >> >> OK, will remove it. >> >> In fact, the order is for performance reason. Imaging there are lots of pasid >entires >> in pasid_cache_list, we remove stale entries first, then in addition code when we >> loop on pasid_cache_list to see if a new pasid entry already exists, we can iterate >> less entries. > >got it. you can mark it in the code. Will do. Thanks Zhenzhong
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