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kvm/tdx: Ignore memory conversion to shared of unassigned region

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TDX requires vMMIO region to be shared.  For KVM, MMIO region is the region
which kvm memslot isn't assigned to (except in-kernel emulation).
qemu has the memory region for vMMIO at each device level.

While OVMF issues MapGPA(to-shared) conservatively on 32bit PCI MMIO
region, qemu doesn't find corresponding vMMIO region because it's before
PCI device allocation and memory_region_find() finds the device region, not
PCI bus region.  It's safe to ignore MapGPA(to-shared) because when guest
accesses those region they use GPA with shared bit set for vMMIO.  Ignore
memory conversion request of non-assigned region to shared and return
success.  Otherwise OVMF is confused and panics there.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20240229063726.610065-35-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Isaku Yamahata 2024-02-29 01:36:55 -05:00 committed by Paolo Bonzini
parent c5d9425ef4
commit 565f4768bb
1 changed files with 12 additions and 0 deletions
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12
accel/kvm/kvm-all.c
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@ -2923,6 +2923,18 @@ int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private)
section = memory_region_find(get_system_memory(), start, size);
mr = section.mr;
if (!mr) {
/*
* Ignore converting non-assigned region to shared.
*
* TDX requires vMMIO region to be shared to inject #VE to guest.
* OVMF issues conservatively MapGPA(shared) on 32bit PCI MMIO region,
* and vIO-APIC 0xFEC00000 4K page.
* OVMF assigns 32bit PCI MMIO region to
* [top of low memory: typically 2GB=0xC000000, 0xFC00000)
*/
if (!to_private) {
return 0;
}
return -1;
}