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UefiCpuPkg: Fix issue that IsModified is wrongly set in PageTableMap
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REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4614

About the IsModified, current function doesn't consider that hardware
also may change the pagetable. The issue is that in the first call of
internal function PageTableLibMapInLevel, the function assume page
table is not changed, and add ASSERT to check. But hardware may change
the page table, which cause the ASSERT happens.
Fix the issue by adding addtional condition to only check if the page
table is changed when the software want to modify the page table.
Also, add more comment to explain this behavior.

Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Crystal Lee <CrystalLee@ami.com.tw>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
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@LiuZhiguang001 @mergify
LiuZhiguang001 authored and mergify[bot] committed Feb 22, 2024
1 parent c10e570 commit 8ccd63d
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Showing 2 changed files with 16 additions and 6 deletions.
4 changes: 3 additions & 1 deletion UefiCpuPkg/Include/Library/CpuPageTableLib.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,9 @@ typedef enum {
Page table entries that map the linear address range are reset to 0 before set to the new attribute
when a new physical base address is set.
@param[in] Mask The mask used for attribute. The corresponding field in Attribute is ignored if that in Mask is 0.
@param[out] IsModified TRUE means page table is modified. FALSE means page table is not modified.
@param[out] IsModified TRUE means page table is modified by software or hardware. FALSE means page table is not modified by software.
If the output IsModified is FALSE, there is possibility that the page table is changed by hardware. It is ok
because page table can be changed by hardware anytime, and caller don't need to Flush TLB.
@retval RETURN_UNSUPPORTED PagingMode is not supported.
@retval RETURN_INVALID_PARAMETER PageTable, BufferSize, Attribute or Mask is NULL.
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18 changes: 13 additions & 5 deletions UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -294,7 +294,7 @@ IsAttributesAndMaskValidForNonPresentEntry (
Page table entries that map the linear address range are reset to 0 before set to the new attribute
when a new physical base address is set.
@param[in] Mask The mask used for attribute. The corresponding field in Attribute is ignored if that in Mask is 0.
@param[out] IsModified TRUE means page table is modified. FALSE means page table is not modified.
@param[in, out] IsModified Change IsModified to True if page table is modified and input parameter Modify is TRUE.
@retval RETURN_INVALID_PARAMETER For non-present range, Mask->Bits.Present is 0 but some other attributes are provided.
@retval RETURN_INVALID_PARAMETER For non-present range, Mask->Bits.Present is 1, Attribute->Bits.Present is 1 but some other attributes are not provided.
Expand All @@ -314,7 +314,7 @@ PageTableLibMapInLevel (
IN UINT64 Offset,
IN IA32_MAP_ATTRIBUTE *Attribute,
IN IA32_MAP_ATTRIBUTE *Mask,
OUT BOOLEAN *IsModified
IN OUT BOOLEAN *IsModified
)
{
RETURN_STATUS Status;
Expand Down Expand Up @@ -587,7 +587,10 @@ PageTableLibMapInLevel (
OriginalCurrentPagingEntry.Uint64 = CurrentPagingEntry->Uint64;
PageTableLibSetPle (Level, CurrentPagingEntry, Offset, Attribute, &CurrentMask);

if (OriginalCurrentPagingEntry.Uint64 != CurrentPagingEntry->Uint64) {
if (Modify && (OriginalCurrentPagingEntry.Uint64 != CurrentPagingEntry->Uint64)) {
//
// The page table entry can be changed by this function only when Modify is true.
//
*IsModified = TRUE;
}
}
Expand Down Expand Up @@ -629,7 +632,10 @@ PageTableLibMapInLevel (
// Check if ParentPagingEntry entry is modified here is enough. Except the changes happen in leaf PagingEntry during
// the while loop, if there is any other change happens in page table, the ParentPagingEntry must has been modified.
//
if (OriginalParentPagingEntry.Uint64 != ParentPagingEntry->Uint64) {
if (Modify && (OriginalParentPagingEntry.Uint64 != ParentPagingEntry->Uint64)) {
//
// The page table entry can be changed by this function only when Modify is true.
//
*IsModified = TRUE;
}

Expand All @@ -654,7 +660,9 @@ PageTableLibMapInLevel (
Page table entries that map the linear address range are reset to 0 before set to the new attribute
when a new physical base address is set.
@param[in] Mask The mask used for attribute. The corresponding field in Attribute is ignored if that in Mask is 0.
@param[out] IsModified TRUE means page table is modified. FALSE means page table is not modified.
@param[out] IsModified TRUE means page table is modified by software or hardware. FALSE means page table is not modified by software.
If the output IsModified is FALSE, there is possibility that the page table is changed by hardware. It is ok
because page table can be changed by hardware anytime, and caller don't need to Flush TLB.
@retval RETURN_UNSUPPORTED PagingMode is not supported.
@retval RETURN_INVALID_PARAMETER PageTable, BufferSize, Attribute or Mask is NULL.
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